A library of six selenorhodamine dyes (4-Se–9-Se) were synthesized, characterized, and evaluated as photosensitizers of TiO2 in dye-sensitized solar cells (DSSCs). The dyes were constructed around either a bis(julolidyl)- or bis(half-julolidyl)-modified selenoxanthylium core functionalized at the 9-position with a thienyl group bearing a carboxylic, hydroxamic, or phosphonic acid for attachment to TiO2. Absorption bands of solvated dyes 4-Se–9-Se were red-shifted relative to the dimethylamino analogues. The dyes adsorbed to TiO2 as mixtures of monomeric and H-aggregated dyes, which exhibited broadened absorption spectra and increased light-harvesting efficiencies relative to the solvated monomeric dyes. Carboxylic acid-bearing dyes 4-Se and 7-Se initially exhibited the highest incident photon-to-current efficiencies (IPCEs) of 65–80% under monochromatic illumination, but the dyes desorbed rapidly from TiO2 into solutions of HCl (0.1 M) in a CH3CN:H2O mixed solvent (120:1 v:v). The hydroxamic acid- and phosphonic acid-bearing dyes 5-Se, 6-Se, 8-Se, and 9-Se exhibited lower IPCEs (49–65%) immediately after preparation of DSSCs; however, the dyes were vastly more inert on TiO2, and IPCEs decreased only minimally with successive measurements under constant illumination. Power-conversion efficiencies (PCEs) of the selenorhodamine-derived DSSCs were less than 1%, probably due to inefficient regeneration of the dyes following electron injection. For a given anchoring group, the bis(half-julolidyl) dyes exhibited higher open-circuit photovoltages and PCEs than the corresponding bis(julolidyl) dyes. The hydroxamic acid- and phosphonic acid-bearing dyes are intriguing photosensitizers of TiO2 in light of their aggregation-induced spectral broadening, high monochromatic IPCEs, and relative inertness to desorption into acidic media.

Extracorporeal photopheresis (ECP) has been used successfully in the treatment of erythrodermic cutaneous T cell lymphoma (CTCL), and other T cell-mediated disorders. Not all patients obtain a significant or durable response from ECP. The design of a selective photosensitizer that spares desirable lymphocytes while targeting malignant T cells may promote cytotoxic T cell responses and improve outcomes after ECP. A series of selenorhodamines built with variations of the Texas red core targeted the mitochondria of malignant T cells, were phototoxic to malignant T cells presumably via their ability to generate singlet oxygen, and were transported by P-glycoprotein (P-gp). To determine the selectivity of the photosensitizers in the ECP milieu, staphylococcal enterotoxin B (SEB)-stimulated and non-stimulated human lymphocytes were combined with HUT-78 cells (a CTCL) to simulate ECP. The amide-containing analogues of the selenorhodamines were transported more rapidly than the thioamide analogues in monolayers of MDCKII-MDR1 cells and, consequently, were extruded more rapidly from P-gp-expressing T cells than the corresponding thioamide analogues. Selenorhodamine 6 with the Texas red core and a piperidylamide functionality was phototoxic to >90% of malignant T cells while sparing >60% of both stimulated and non-stimulated T cells. In the resting T cells, (63 ± 7)% of the CD4+ T cell compartment, and (78 ± 2.5)% of the CD8+ cytotoxic T cell population were preserved, resulting in an enrichment of healthy and cytotoxic T cells after photodepletion.

Extended thio- and selenorhodamines with a linear or angular fused benzo group were prepared. The absorption maxima for these compounds fell between 640 and 700 nm. The extended rhodamines were evaluated for their potential as photosensitizers for photodynamic therapy in Colo-26 cells. These compounds were examined for their photophysical properties (absorption, fluorescence, and ability to generate singlet oxygen), for their dark and phototoxicity toward Colo-26 cells, and for their co-localization with mitochondrial-specific agents in Colo-26 and HUT-78 cells. The angular extended rhodamines were effective photosensitizers toward Colo-26 cells with 1.0 J cm−2 laser light delivered at λmax ± 2 nm with values of EC50 of (2.8 ± 0.4) × 10−7 M for sulfur-containing analogue 6-S and (6.4 ± 0.4) × 10−8 M for selenium-containing analogue 6-Se. The linear extended rhodamines were effective photosensitizers toward Colo-26 cells with 5 and 10 J cm−2 of broad-band light (EC50’s ⩽ 2.4 × 10−7 M).

Extended rhodamines were prepared by inserting an additional fused benzene ring into the rhodamine xanthylium core. The synthesis of “bent” dyes 4-E (E = S, Se, Te) began with regioselective lithiation of the 1-position of N,N-diisopropyl 6-dimethylamino-2-naphthamide (11b) with n-BuLi/TMEDA (≥25:1 1- vs 3-lithiation) followed by addition of a dichalcogenide electrophile. The synthesis of “linear” dyes 5-E (E = S, Se, Te) began with regioselective lithiation of the 3-position of N,N-diethyl 6-dimethylamino-2-naphthamide (11a) with lithium tetramethylpiperidide (≥50:1 3- vs 1-lithiation) followed by addition of a dichalcogenide electrophile. Dyes 4-E and 5-E have absorption maxima in the 633–700 nm range. Dyes 4-E generate singlet oxygen upon irradiation while dyes 4-S and 5-S are highly fluorescent, with quantum yields for fluorescence of 0.47 and 0.18, respectively. DFT calculations were performed on the 4-E and 5-E chromophores. For the dyes 4-E, the lowest energy excitation is due solely to the HOMO–LUMO transition. For dyes 5-E, the lowest energy excitation is a combination of two excitations, both having contributions from the HOMO to LUMO and HOMO-1 to LUMO.

Surfaced enhanced Raman scattering (SERS) nanotags operating with 1280 nm excitation were constructed from reporter molecules selected from a library of 14 chalcogenopyrylium dyes containing phenyl, 2-thienyl, and 2-selenophenyl substituents and a surface of hollow gold nanoshells (HGNs). These 1280 SERS nanotags are unique as they have multiple chalcogen atoms available which allow them to adsorb strongly onto the gold surface of the HGN thus producing exceptional SERS signals at this long excitation wavelength. Picomolar limits of detection (LOD) were observed and individual reporters of the library were identified by principal component analysis and classified according to their unique structure and SERS spectra.

Biofouling on ships and boats, characterized by aquatic bacteria and small organisms attaching to the hull, is an important global issue, since over 80000 tons of antifouling paint is used annually. This biofilm, which can form in as little as 48 hours depending on water temperature, increases drag on watercraft, which greatly reduces their fuel efficiency. In addition, biofouling can lead to microbially induced corrosion (MIC) due to H2S formed by the bacteria, especially sulfate-reducing bacteria.When the International Maritime Organization (IMO) international convention banned the use of effective but environmentally damaging coatings containing tributyl tin in 2008, the development of clean and effective antifouling systems became more important than ever. New nonbiocidal coatings are now in high demand. Scientists have developed new polymers, materials, and biocides, including new elastomeric coatings that they have obtained by improving the original silicone (polydimethylsiloxane) formulation patented in 1975. However, the high cost of silicones, especially of fluoropolymer-modified silicones, has generally prevented their large-scale diffusion. In 2009, traditional antifouling coatings using cuprous oxide formulated in copolymer paints still represented 95% of the global market volume of anti-fouling paints.The sol–gel nanochemistry approach to functional materials has emerged as an attractive candidate for creating low fouling surfaces due to the unique structure and properties of silica-based coatings and of hybrid inorganic–organic silicas in particular. Sol–gel formulations easily bind to all types of surfaces, such as steel, fiberglass, aluminum, and wood. In addition, they can cure at room temperature and form thin glassy coatings that are markedly different from thick silicone elastomeric foul-releasing coatings. Good to excellent performance against biofouling, low cure temperatures, enhanced and prolonged chemical and physical stability, ease of application, and the waterborne nature of sol–gel coatings all support the diffusion of these paints to efficiently reduce the accumulation of fouling layers on valued surfaces immersed in marine or fluvial waters. Furthermore, sol–gel glassy coatings are transparent and can be effectively applied to optical devices, windows, and solar panels used in lake, fluvial, or marine environments.Sol–gel technology is eminently versatile, and the first generation sol–gel paints have already shown good performance. Even so, vast opportunities still exist for chemists to develop novel sol–gel derived coatings to both prevent biofouling and enhance the hydrodynamic properties of boat and ship hulls. Moreover, researchers have prepared and applied multifunctional sol–gel coatings providing protection against both biofouling and corrosion. They have tested these in the marine environment with good preliminary results.In this Account, we discuss some of our new strategies for the controlled functionalization of surfaces for the development of efficient antifouling and foul-releasing systems and summarize the main achievements with biocidal and nonbiocidal sol–gel coatings. We conclude by giving insight into the marine coatings and sol–gel products markets, providing arguments to justify our conclusion that the sol–gel coatings technology is now a mature platform for the development of economically viable and environmentally friendly antifouling and foul-release formulations of enhanced performance.

We examined a series of selenorhodamines with amide and thioamide functionality at the 5-position of a 9-(2-thienyl) substituent on the selenorhodamine core for their potential as photosensitizers for photodynamic therapy (PDT) in P-glycoprotein (P-gp) expressing cells. These compounds were examined for their photophysical properties (absorption, fluorescence, and ability to generate singlet oxygen), for their uptake into Colo-26 cells in the absence or presence of verapamil, for their dark and phototoxicity toward Colo-26 cells, for their rates of transport in monolayers of multidrug-resistant, P-gp-overexpressing MDCKII-MDR1 cells, and for their colocalization with mitochondrial specific agents in Colo-26 cells. Thioamide derivatives 16b and 18b were more effective photosensitizers than amide derivatives 15b and 17b. Selenorhodamine thioamides 16b and 18b were useful in a combination therapy to treat Colo-26 cells in vitro: a synergistic therapeutic effect was observed when Colo-26 cells were exposed to PDT and treatment with the cancer drug doxorubicin.

Analogues of Texas red incorporating the heavy chalcogens S, Se, and Te atoms in the xanthylium core were prepared from the addition of aryl Grignard reagents to appropriate chalcogenoxanthone precursors. The xanthones were prepared via directed metalation of amide precursors, addition of dichalcogenide electrophiles, and electrophilic cyclization of the resulting chalcogenides with phosphorus oxychloride and triethylamine. The Texas red analogues incorporate two fused julolidine rings containing the rhodamine nitrogen atoms. Analogues containing two “half-julolidine” groups (a trimethyltetrahydroquinoline) and one julolidine and one “half-julolidine” were also prepared. The photophysics of the Texas red analogues were examined. The S-analogues were highly fluorescent, the Se-analogues generated single oxygen (1O2) efficiently upon irradiation, and the Te-analogues were easily oxidized to rhodamines with the telluroxide oxidation state. The tellurorhodamine telluroxides absorb at wavelengths ≥690 nm and emit with fluorescence maxima >720 nm. A mesityl-substituted tellurorhodamine derivative localized in the mitochondria of Colo-26 cells (a murine colon carcinoma cell line) and was oxidized in vitro to the fluorescent telluroxide.

Diaryl ditellurides were oxidized in situ to give aryltellurinic acids, which catalyzed the oxidation of NaBr with H2O2 in buffered aqueous solutions. The aryltellurinic acids were slowly oxidized under the reaction conditions to the corresponding telluronic acids, which did not catalyze oxidation of NaBr with H2O2. Both 4-(methoxyphenyl)tellurinic acid and 4-(methoxyphenyl)telluronic acid were characterized in solution by 125Te NMR and for their effectiveness as catalysts in kinetics studies. The effectiveness of the tellurinic acids as catalysts was very sensitive to electron demand in the intermediates present during the course of the reaction. Electron-withdrawing substituents favor the deprotonated tellurinic acid (tellurinate) in solution, while electron-donating substituents favor the protonated tellurinic acid. Of the nine ditellurides screened for their ability to accelerate the oxidation of NaBr with H2O2, diphenyl ditelluride emerged as the most active. The addition of only 0.20 mol % of this ditelluride (relative to substrate) promoted a 240-fold increase in the rate of oxidation of NaBr with H2O2, as measured by the bromination of 4-pentenoic acid. The “Br+” species prepared in situ were trapped by a series of alkenoic acids and activated aryl compounds.

Several 9-aryl-3,6-diaminotelluroxanthylium dyes with phenyl, 2-methylphenyl, and 2,4,6-trimethylphenyl substituents at the 9-position were prepared. The characterization of these compounds included determination of 125Te NMR spectra, fluorescence quantum yields (ΦF), and quantum yields for the generation of singlet oxygen [Φ(1O2)]. While these compounds were essentially nonfluorescent (ΦF < 0.005), they produce 1O2 with Φ(1O2) between 0.43 and 0.90. The tellurorosamines were oxidized with 1O2 via self-photosensitization to the corresponding telluroxides, which allowed their preparation free of excess oxidant. Telluroxides with a 9-(2-methylphenyl) or 9-(2,4,6-trimethylphenyl) substituent were fluorescent with quantum yields for fluorescence between 0.20 and 0.31. Steric bulk at the 9-position of the resulting telluroxides impacted rates of inter- and intramolecular attack of nucleophiles and stability of the telluroxide in aqueous media near physiological pH. The yield of reduction of the telluroxide with glutathione was also dependent on the steric bulk of the 9-aryl substituent. The structure of products from oxidation of the 9-(4-bromophenyl) tellurorosamine was determined by X-ray crystallography and indicated the addition of oxygen nucleophiles to the 9-position of the telluroxide oxidation state of the tellurorosamine.

•We have used transient absorption spectroscopy to measure relative electron-injection yields from selenorhodamine dyes to titanium dioxide.•Electrons were injected approximately twice as efficiently from dyes anchored to TiO2 via carboxylate linkages than via phosphonate linkages.•For a given anchoring mode, electrons were injected approximately twice as efficiently from H-aggregated dyes than from non-aggregated dyes.We used transient absorption spectroscopy to characterize excited-state electron injection from a 2,7-bis(dimethylamino)-9-(5-phosphonothien-2-yl)selenoxanthylium dye (3-Se) into TiO2. Dye 3-Se adsorbed to TiO2 via the phosphonic acid group as a mixture of H-aggregates and monomers. Injection of electrons from photoexcited 3-Se into TiO2 yielded the dication radical (3-Se+) and an associated transient absorption at wavelengths shorter than 540 nm, the amplitude of which was proportional to the quantum yield of electron injection (ϕinj). Our data revealed that ϕinj from H-aggregated 3-Se was (2.0 ± 1.3)-fold greater than from monomeric 3-Se; therefore, H-aggregation increased the efficiencies of both light-harvesting and electron injection. Comparison with our reported data for the analogous carboxylic acid-functionalized dye (1-Se) revealed that ϕinj via the carboxylate linkage was (2.3 ± 1.1)-fold greater than via the phosphonate linkage. Thus, electron-injection reactivity is sensitive to both the aggregation state and the surface-anchoring mode of these chalcogenorhodamine dyes. The decrease of ϕinj for 3-Se is offset by its enhanced stability and persistence on TiO2, rendering the phosphonic acid-functionalized and H-aggregated dye a particularly attractive sensitizer.

Chalcogenopyrylium monomethine dyes were prepared via condensation of a 4-methylchalcogenopyrylium compound with a chalcogenopyran-4-one bearing a 4-(diethoxyphosphoryl)phenyl substituent (or the phosphonic acid derivative). The dyes have absorbance maxima of 603–697 nm in the window where the solar spectrum is most intense. The dyes formed H-aggregates on TiO2, increasing the light-harvesting efficiency of the dyes. Shortcircuit photocurrent action spectra were acquired to evaluate the influence of dye structure on the photoelectrochemical performance.

Twenty-seven chalcogenopyrylium derivatives varying in the heteroatom of the pyrylium core and substituents at the 2-, 4-, and 6-positions were examined for their effect on human MRP1-mediated uptake of tritiated estradiol glucuronide into inside-out membrane vesicles, their affinity for and ability to stimulate the ATPase activity of purified human P-glycoprotein (P-gp)-His10, and their ability to promote uptake of calcein AM and vinblastine in multidrug-resistant cells. Differences in their effects on MRP1 and P-gp activity were noted, and a second set of thiopyrylium compounds with systematic substituent changes was examined to refine these differences further. Derivatives with tert-butyl substituents in the 2- and 6-positions had the lowest inhibitory activity toward both transporters. Derivatives with thioamide functionality in the 4-position were more active against MRP1 than derivatives with amide functionality. Conversely, derivatives with amide functionality in the 4-position were more active in P-gp than derivatives with thioamide functionality.

Twelve thiorhodamine derivatives have been examined for their ability to stimulate the ATPase activity of purified human P-glycoprotein (P-gp)-His10, to promote uptake of calcein AM and vinblastine into multidrug-resistant, P-gp-overexpressing MDCKII-MDR1 cells, and for their rates of transport in monolayers of multidrug-resistant, P-gp-overexpressing MDCKII-MDR1 cells. The thiorhodamine derivatives have structural diversity from amide and thioamide functionality (N,N-diethyl and N-piperidyl) at the 5-position of a 2-thienyl substituent on the thiorhodamine core and from diversity at the 3-amino substituent with N,N-dimethylamino, fused azadecalin (julolidyl), and fused N-methylcyclohexylamine (half-julolidyl) substituents. The julolidyl and half-julolidyl derivatives were more effective inhibitors of P-gp than the dimethylamino analogues. Amide-containing derivatives were transported much more rapidly than thioamide-containing derivatives.

We used transient absorption spectroscopy to characterize excited-state electron injection from a 2,7-bis(dimethylamino)-9-(2-thienyl-5-carboxy)selenoxanthylium dye (1-Se) and a 2,7-bis(dimethylamino)-9-(3-thienyl-2-carboxy)selenoxanthylium dye (2-Se) to TiO2. Monolayers of 1-Se on nanocrystalline TiO2 films consisted of both H-aggregated and nonaggregated dyes, whereas 2-Se underwent little or no aggregation upon adsorption. Two transient spectral signals were correlated with the dication radicals (1-Se+ and 2-Se+) generated by electron injection: an absorption at wavelengths shorter than 540 nm and a bleach from approximately 540−650 nm. Relative quantum yields for electron injection (ϕinj) were calculated from the measured amplitudes of these signals. The value of ϕinj for H-aggregated 1-Se was approximately 2-fold greater than ϕinj for nonaggregated 1-Se and approximately 3-fold greater than ϕinj for nonaggregated 2-Se. Thus, H-aggregation can increase both the light-harvesting efficiencies and the electron-injection yields of rhodamine derivatives. Our findings suggest that controlled aggregation of organic dyes may represent an attractive strategy for improving the global energy-conversion efficiencies of organic dye-sensitized solar cells and photocatalysts.

Rhodamine photosensitizers (PSs) substituting S or Se for O in the xanthene ring give turnover numbers (TONs) as high as 9000 for the generation of hydrogen via the reduction of water using [CoIII(dmgH)2(py)Cl] (where dmgH = dimethylglyoximate and py = pyridine) as the catalyst and triethanolamine as the sacrificial electron donor. The turnover frequencies were 0, 1700, and 5500 mol H2/mol PS/h for O, S, and Se derivatives, respectively (ΦH2 = 0%, 12.2%, and 32.8%, respectively), which correlates well with relative triplet yields estimated from quantum yields for singlet oxygen generation. Phosphorescence from the excited PS was quenched by the sacrificial electron donor. Fluorescence lifetimes were similar for the O- and S-containing rhodamines (∼2.6 ns) and shorter for the Se analog (∼0.1 ns). These data suggest a reaction pathway involving reductive quenching of the triplet excited state of the PS giving the reduced PS− that then transfers an electron to the Co catalyst. The longer-lived triplet state is necessary for effective bimolecular electron transfer. While the cobalt/rhodamine/triethanolamine system gives unprecedented yields of hydrogen for the photoreduction of water, mechanistic insights regarding the overall reaction pathway as well as system degradation offer significant guidance to developing even more stable and efficient photocatalytic systems.

21,23-Ditelluraporphyrins 3, 9, and 16−18 bearing phenyl, 4-methoxyphenyl, and/or 3,4,5-trimethoxyphenyl meso substituents were prepared by the condensation of 2,5-di[hydroxy(aryl)methyl]tellurophenes 12 with 2,5-di[2-pyrrolo(aryl)methyl]tellurophenes 15 in the presence of BF3−etherate followed by oxidation with p-chloranil. Compounds 15 were prepared from tellurophenes 12 with pyrrole and BF3−etherate. Tellurophenes 12 were prepared in 44−72% isolated yield by the addition of 1,6-diarylhexa-2,4-diyn-1,6-diols 13 to the reduction product of Te powder and LiBHEt3. No additional Lewis acid was necessary in these reactions. Coupling of 1-aryl-2-propyn-1-ols (14) with CuCl, pyridine, and air in MeOH gave diyndiols 13. 26,28-Ditellurasapphyrin 10 was isolated in 0.6% yield from the reaction mixture that produced 9 in 12% isolated yield. The X-ray structure of 10 showed a nearly planar sapphyrin core with the Te atoms of both tellurophene rings pointing to the center of the core. 30,33-Ditellurarubyrin 11 was isolated in 32% yield by the reaction of two equivalents of trifluoroacetic acid with tellurophene dipyrrane 15c. 125Te NMR spectra were recorded for the compounds of this study.

We have examined 46 tetramethylrosamine/rhodamine derivatives with structural diversity in the heteroatom of the xanthylium core, the amino substituents of the 3- and 6-positions, and the alkyl, aryl, or heteroaryl group at the 9-substituent. These compounds were examined for affinity and ATPase stimulation in isolated MDR3 CL P-gp and human P-gp-His10, for their ability to promote uptake of calcein AM and vinblastine in multidrug-resistant MDCKII−MDR1 cells, and for transport in monolayers of MDCKII−MDR1 cells. Thioamide 31-S gave KM of 0.087 μM in human P-gp. Small changes in structure among this set of compounds affected affinity as well as transport rate (or flux) even though all derivatives examined were substrates for P-gp. With isolated protein, tertiary amide groups dictate high affinity and high stimulation while tertiary thioamide groups give high affinity and inhibition of ATPase activity. In MDCKII−MDR1 cells, the tertiary thioamide-containing derivatives promote uptake of calcein AM and have very slow passive, absorptive, and secretory rates of transport relative to transport rates for tertiary amide-containing derivatives. Thioamide 31-S promoted uptake of calcein AM and inhibited efflux of vinblastine with IC50’s of ∼2 μM in MDCKII−MDR1 cells.

Various 1-[[bis(1-methylethyl)amino]carbonyl]-2-(dibromo-n-alkylseleno)ferrocene derivatives reacted with 2 equiv of 4-pentenoic acid or 5-hexenoic acid to give the corresponding γ- or δ-lactones, respectively, from transfer of the alkyl group bound to selenium to the terminal alkene carbon. In the lactone cyclization, 1-[[bis(1-methylethyl)amino]carbonyl]-2-(bromoselenenyl)ferrocene (25) is formed and reacts with a second equivalent of the alkenoic acid to give either 5-[1-[[bis(1-methylethyl)amino]carbonyl]ferrocene-2-selenenylmethyl]tetrahydro-2-furanone (23) or 6-[1-[[bis(1-methylethyl)amino]carbonyl]ferrocene-2-selenenylmethyl]tetrahydro-2H-pyran-2-one (26) as a mixture of diastereomers in yields comparable to the corresponding γ- or δ-lactone. The addition of 1-[[bis(1-methylethyl)amino]carbonyl]-2-(dibromo-n-butylseleno)ferrocene to 3-butenoic acid gave alkyl transfer to the internal alkene carbon and formation of the γ-lactone. Density functional theory (DFT) geometry optimizations were performed on several idealized n-alkyldibromselenoferrocene structures to examine the role of iron in the alkyl transfer and the role of various structural features on the alkyl carbon−selenium bond length. The results of the computations suggested that the ferrocenyl iron was not involved in the alkyl transfer reactions.

The multidrug efflux pump P-glycoprotein (Pgp) couples drug transport to ATP hydrolysis. Previously, using a synthetic library of tetramethylrosamine (TMR) analogues, we observed significant variation in ATPase stimulation (VmD). Concentrations required for half-maximal ATPase stimulation (KmD) correlated with ATP hydrolysis transition-state stabilization and ATP occlusion (EC50D) at a single site. Herein, we characterize several TMR analogues that elicit modest turnover (kcat ≤ 1–2 s−1) compared to verapamil (VER) (kcat ∼ 10 s−1). Apparent ATPase activities manifest as nearly equivalent to basal values. In some cases, KmD parameters for drug stimulation of ATPase could not be accurately determined, yet these same TMR analogues promoted ATP occlusion at relatively low concentrations (∼0.4–40 µM). Moreover, the TMR analogues competitively inhibited VER-dependent ATPase activity at concentrations similar to those required for ATP occlusion. Finally, the TMR analogues facilitated uptake of calcein-AM into CR1R12 and MDCK-MDR1 cells and are actively transported by Pgp in monolayers of MDCK-MDR1 cells at similarly low concentrations (∼1–20 µM). ADP·Vi release kinetics were identical in the presence of the TMR derivatives, VER, or in the absence of drug, suggesting that slow turnover is not likely due to slow release of the ATP hydrolysis products ADP and Pi. These data support the partition model in which drug site occupancy converts residual basal ATPase activity to a drug-dependent mechanism even in cases where stimulation appears to be exactly compensatory to basal values. It is noteworthy that when compared to previously reported TMR analogues, subtle modification of the TMR scaffold can confer large differences in ATP turnover.

A series of chalcogenopyrylium dyes were evaluated as modulators/inhibitors of P-glycoprotein (Pgp). Their ability to inhibit verapamil (VER)-dependent ATPase activity (IC50 values) in lipid-activated, mouse Cys-less mdr3 Pgp was determined. Their ability to promote calcein-AM (CAM) uptake in MDCKII-MDR1 cells and their capacity to be transported by Pgp in monolayers of MDCKII-MDR1 cells were also evaluated. The chalcogenopyrylium dyes promoted CAM uptake with values of EC50 between 5 × 10−6 and 3.5 × 10−5 M and 7 of the 9 dyes examined in transport studies were substrates for Pgp with efflux ratios (PBA/AB) between 14 and 390. Binding of three compounds (1-S, 3-S, and 4-S) to Pgp was also assessed by fluorescence. These three thiopyrylium dyes showed increased fluorescence upon binding to Pgp, giving apparent binding constants, Kapp, on the order of 10−7 to 10−6 M. Compound 8-Te was particularly intriguing since it appeared to influence Pgp at low micromolar concentrations as evidenced by its influence on VER-stimulated ATPase activity (IC50 of 1.2 × 10−6 M), CAM uptake (EC50 of 5.4 × 10−6 M), as well as [3H]-vinblastine transport by Pgp in cells (IC50 of 4.3 × 10−6 M) and within inside-out membrane vesicles (IC50 of 9.6 × 10−6 M). Yet, Pgp did not influence the distribution of 8-Te in MDCKII-MDR1 monolayers suggesting that 8-Te may bind to an allosteric site.A series of chalcogenopyrylium compounds were evaluated as inhibitors/modulators of P-glycoprotein in lipid-activated protein, inside-out membrane vesicles, and in human MDCKIIMDR1 cells.

The DNA binding efficacy and preferred mode of binding of a series of rhodamine-related chalcogenoxanthylium dyes was investigated by isothermal titration calorimetry (ITC) using ctDNA, [poly(dCdG)]2 and [poly(dAdT)]2, and by a topoisomerase I DNA unwinding (Topo I) assay. The dyes of this study showed tight binding to ctDNA with binding constants, Kb, on the order of 106–107 M−1. The ITC and Topo I assay studies suggested that the 9-substituent has a strong impact on binding modes ranging from an apparent preference for intercalation with a 9-2-thienyl substituent (similar binding to [poly(dCdG)]2 and [poly(dAdT)]2, re-supercoiling of DNA in the Topo I assay at <10−5 M dye), to mixed binding modes with 9-phenyl derivatives (2- to 3-fold preference for binding to [poly(dAdT)]2, re-supercoiling of DNA in the Topo I assay at ∼2 × 10−5 M dye), to minor groove binding in a 9-(2-thienyl-5-diethylcarboxamide) derivative (strong preference for binding to [poly(dAdT)]2, did not show complete re-supercoiling in the Topo I assay). No binding to ctDNA was observed in one derivative with a 9-(3-thienyl-2-diethylcarboxamide) substituent, which cannot be co-planar with the xanthylium core. In series of dyes where the chalcogen atom was varied, the selenoxanthylium derivatives had 2- to 3-fold higher values of Kb than the corresponding xanthylium, thioxanthylium, or telluroxanthylium derivatives, which all showed comparable values of Kb. The chalcogen atom appeared to have little influence on binding mode.The binding of a series of rhodamine-related chalcogenoxanthylium dyes to DNA was measured using isothermal titration calorimetry and a topoisomerase I DNA unwinding assay.

A series of thio- and selenopyrylium analogues of 2,4-di(4-dimethylaminophen-yl)-6-methylthiopyrylium iodide were prepared in five steps from 4-dimethylaminophenyl-propargyl aldehyde and the corresponding lithium acetylide. When bound to DNA, all of the dyes absorb at wavelengths >600 nm, which avoids the hemoglobin band I maximum at 575 nm. The binding of the series of dyes to double-stranded DNA was examined spectrophotometrically and by isothermal titration calorimetry to determine binding constants, by a topoisomerase I DNA unwinding assay, by competition dialysis with [poly(dGdC)]2 and [poly(dAdT)]2, and by ethidium bromide displacement studies to examine propensities for intercalation, and by circular dichroism studies. The dyes were found to show mixed binding modes.A series of thio- and seleno-analogues of 2,4-di(4-dimethylaminophenyl)-6-methylthiopyrylium iodide was prepared and the binding of these dyes to DNA was examined spectrophotometrically, by isothermal titration calorimetry, by a topoisomerase I assay, by competition dialysis, and by circular dichroism spectroscopy.

21,23-Dithiaporphyrins (2–10) were designed and prepared as analogues of 5,20-diphenyl-10,15-bis(4-carboxylatomethoxy)phenyl-21,23-dithiaporphyrin (1) to examine the impact of steric bulk at the 5- and 20-meso positions as well as the impact of symmetry. Changes at the meso positions had minimal impact on the UV–vis–near-IR absorption spectra, quantum yields for the generation of singlet oxygen, and quantum yields for fluorescence and some impact on values of the octanol/water partition coefficient. Of the compounds 1–10, 5-phenyl-20-(2-thienyl)-10,15-bis-(4-carboxylatomethoxy-phenyl)-21,23-dithiaporphyrin (3) showed the greatest phototoxicity toward cultured R3230AC cells, with 68% cell kill at 1 × 10−7 M and irradiation with 5 J cm−2 of 350–750 nm light. Results in this study suggest that smaller substituents on the meso ring and less symmetrical compounds are more effective as photosensitizers than compounds with two bulky substituents at adjoining meso sites and a higher symmetry. The mitochondria appear to be involved in the process of phototoxicity as determined by the inhibition of whole cell cytochrome c oxidase activity in cells treated with 3 and light. No impact upon mitochondrial cytochrome c oxidase activity was observed in cells treated with 3 and no light. Fluorescence microscopy studies suggest that the mitochondria are not initial sites of accumulation of 3.

Several thio and seleno analogues of tetramethylrosamine (TMR) were prepared. Thio derivatives of TMR have absorption maxima near 570 nm, while seleno derivatives of TMR have absorption maxima near 580 nm. The 3- or 4-N,N-dimethylaminophenyl substituent in the 9-position greatly increases internal conversion, which lowers quantum yields for fluorescence and the generation of singlet oxygen. Thio and seleno analogues of TMR are effective photosensitizers against chemosensitive AUXB1 cells in vitro and against multidrug-resistant CR1R12 cells in vitro, which have been treated with verapamil. The CR1R12 cells accumulated significantly lower concentrations of the photosensitizers relative to the AUXB1 cells presumably due to the expression of P-glycoprotein (Pgp) in the CR1R12 cells. Following treatment with 5 × 10−5 M verapamil, the uptake in CR1R12 cells of several fluorescent thio analogues of TMR is comparable to that observed for the chemosensitive AUXB1 cells.A series of substituted thio and seleno analogues of tetramethylrosamine were prepared and evaluated as photosensitizers against chemosensitive AUXB1 cells and multidrug-resistant CR1R12 cells.

Thio- and selenoxanthylium dyes were prepared by the addition of 2-lithiothiophene, 4-N,N-dimethylaminophenylmagnesium bromide, and 1-naphthylmagnesium bromide to the appropriate 2,7-bis-N,N-dimethylaminochalcogenoxanthen-9-one, followed by dehydration and ion exchange to the chloride salts. The corresponding chalcogenoxanthylium dyes were evaluated as photosensitizers for the inactivation of intracellular and extracellular virus in red blood cell suspensions and for the inactivation of selected strains of gram (+) and gram (−) bacteria in red blood cell suspensions. Selected combinations of photosensitizer and light gave >6 log10 inactivation of intracellular and extracellular virus, and >4 log10 inactivation of extracellular bacteria with varying levels of hemolyis, following a 42-day storage of red blood cell suspensions. Photocleavage experiments with plasmid DNA and the chalcogenoxanthylium dyes suggested the genomic material contained in the virus and in the bacteria as one possible target for the photodynamic action of some of these dyes.A series of substituted thio- and seleno-analogues of tetramethylrosamine was prepared and evaluated as photosensitizers for the photodynamic purging of blood-borne viral and bacterial pathogens.

Tetramethylrosamine and its thio- and seleno- analogues (TMR-O, TMR-S, and TMR-Se, respectively) were examined for their ability to be transported by Pgp into chemo-resistant CR1R12 cells. Verapamil (7 × 10−6 M) enhanced the uptake of TMR-O and TMR-S into CR1R12 cells compared to those cultures not previously exposed to verapamil. The uptake of TMR-O and TMR-S in CR1R12 cells in the presence of 7 × 10−6 M verapamil was equivalent to its uptake in the chemo-sensitive parent cell line AUXB1 in the absence or presence of verapamil. None of the TMR analogues were effective alone as photosensitizers of CR1R12 cells. However, when either TMR-S or TMR-Se was added to CR1R12 cells after 7 × 10−6 M verapamil exposure for 2 h, irradiation of cultures with 5.0 J cm−2 of 350–750 nm light caused significant phototoxicity. TMR-O showed no significant phototoxicity in the presence of verapamil. Chemo-sensitive AUXB1 cells are equally susceptible to phototoxicity using TMR-Se with or without previous exposure to verapamil. The Pgp modulators verapamil and CsA increased the uptake of CAM into CR1R12. Exposure of CR1R12 cells to TMR-S or TMR-Se for 2 h in the dark resulted in no significant change in the intracellular accumulation of CAM. However, 1 h of light exposure after incubation of cells with TMR-S or TMR-Se resulted in an up to 2-fold increase in CAM uptake.

2,6-Bis(4-anilino)-4-(4-N,N-dimethylanilino)thiopyrylium chloride (AA1) and -selenopyrylium chloride (AA1-Se) and 2,6-bis(4-anilino)-4-(4-N-morpholinophenyl)thiopyrylium chloride (1) and -selenopyrylium chloride (2) were prepared via the addition of 4-N,N-dimethylanilino magnesium bromide and 4-N-morpholinophenyl magnesium bromide to chalcogenopyranones 3 followed by treatment with HCl gas then water. Cellular uptake of these dyes varied from 12 ± 3 fmol/cell for AA1 to 150 ± 40 fmol/cell for AA1-Se. upon exposure to 5 × 10−5 M solutions of the dyes for 3 h. Exposure of cell cultures to 1.8 J/cm2 of 360–750-nm light following incubation with 1 × 10−6 M of either AA1, 1, or 2 for 24 h resulted in no significant additional phototoxicity while AA1-Se showed a significant (P<0.05) reduction in cell viability from 81% to 46%. Thiopyrylium dyes AA1 and 1 showed significant dark toxicity relative to selenopyrylium dyes AA1-Se and 2, respectively. AA1 was the only one of the four dyes to show inhibition of whole-cell mitochondrial cytochrome c oxidase activity in the dark. Irradiation of whole cells or mitochondrial suspensions treated with AA1, AA1-Se, or 2 gave inhibition of mitochondrial cytochrome c oxidase activity. Studies of JC-1-efflux indicated that all four cationic dyes accelerated the loss of JC-1 from the mitochondria, which suggests that all four dyes target the mitochondria.Graphic

Thio and seleno analogues of tetramethylrosamine were prepared by the directed-metalation/cyclization of the corresponding N,N-diethyl 2-(3-dimethylaminophenylchalcogeno)-4-dimethylaminobenzamide to the 2,7-bis-(N,N-dimethylamino)-9H-chalcogenoxanthen-9-one followed by the addition of phenylmagnesium bromide, dehydration, and ion exchange to the chloride salt. The thio and seleno tetramethylrosamines had longer wavelengths of absorption and higher quantum yields for the generation of singlet oxygen than tetramethylrosamine. Both the thio and selenoanalogues of tetramethylrosamine were efficient photosensitizers against R3230AC rat mammary adenocarcinoma cells in vitro.Graphic

Surfaced enhanced Raman scattering (SERS) nanotags operating with 1280 nm excitation were constructed from reporter molecules selected from a library of 14 chalcogenopyrylium dyes containing phenyl, 2-thienyl, and 2-selenophenyl substituents and a surface of hollow gold nanoshells (HGNs). These 1280 SERS nanotags are unique as they have multiple chalcogen atoms available which allow them to adsorb strongly onto the gold surface of the HGN thus producing exceptional SERS signals at this long excitation wavelength. Picomolar limits of detection (LOD) were observed and individual reporters of the library were identified by principal component analysis and classified according to their unique structure and SERS spectra.