A series of metallo Ru(II), Fe(II), Co(II) bisterpyridine polymers were prepared with naphthalene diimide (NDI) groups inserted between two 4′-phenyl-2,2:6′,2′′-terpyridine (phtpy) groups. Core-substituted NDIs typically have long-lived excited states with relatively high quantum yields, yet the NDI emission in these metallopolymers was completely quenched, most likely because of efficient electron-transfer from the M(phtpy)22+ groups to the excited NDIs. AFM, TEM and SEM experiments indicate that the regiochemistry of the substitution on the core of the naphthalene diimide, together with coordination of the terpyridine ligand to different metals, strongly influences the morphologies of the resulting metallosupramolecular polymers. The morphologies of spin-coated samples of the para-substituted polymers revealed the formation of long, bundled nanorods. Lengths on the order of ∼8 μm were observed for the bundle of the longest polymers (5-Ru) by both AFM and TEM microscopy. The morphologies of the meta substituted polymers, on the other hand, exhibited significantly shorter and less well-defined morphologies.

The two tautomeric forms of N-confused tetraphenylporphyrin (NCTPP) show distinctly different absorption spectra. The existence of each tautomer in solution has been shown to be strongly solvent-dependent. In the present work, we have studied the tautomerization using absorption spectroscopy in 15 different solvents. While changes in the two tautomers are not large in the Soret band region, the distinct spectral changes between the two tautomers in the Q-band region provide a convenient way to measure the concentration of each tautomer. The resulting data shows a strong correlation between the tautomer and the H-bond accepting ability of the solvent. The anomaly in this data is for the alcoholic solvents ethanol and methanol, for which we observe evidence for H-bonding, presumably between the exterior N2 nitrogen of the NCTPP and the O–H proton of the solvent.

Two monosubstituted and one tetrasubstituted N-confused porphyrins (1–3) were prepared in ca. 3–5% yields using a [2 + 2] synthesis. The monosubstituted porphyrins have carbomethoxy (1) or nitro (2) substituents on one of the meso-phenyl groups, while the meso-phenyl groups of the third NCP (3) are substituted with nitro, bromo, and methyl groups in an AB2C pattern. The specific regiochemistry of the aryl rings around the macrocycle in each porphyrin was definitively determined using a combination of 1D (1H and 13C) and 2D (gHMBC, gHSQC and ROESY) NMR spectroscopy. The absorption spectra of 1–3 in CH2Cl2 are similar to those of N-confused tetraphenylporphyrin (NCTPP) but have Soret and Q bands that are shifted to lower energies with smaller extinction coefficients in comparison to those for NCTPP.

The self-assembly of bolaamphiphile 1 into nanotubes containing a nanostructured electron donor/acceptor heterojunction is reported. In 10% MeOH/H2O, the tetraphenylporphyrin (TPP) and 1,4,5,8-naphthalenetetracarboxylic acid diimide chromophores engage in strong J-type π–π interactions within monolayer rings that further stack into the nanotube assemblies. In 10% MeOH/H2O at pH 1 or 11 or in pure MeOH, assembly is driven exclusively by the TPP ring, leading to the formation of nonspecific, unstructured aggregates. Steady-state, time-resolved fluorescence and femtosecond transient absorption spectroscopy revealed a strong dependence of the fluorescence decay and electron-transfer/charge-recombination time constants on the nature of the assemblies. These studies highlight the importance of local nanostructure in determining the photophysical properties of optoelectronic materials.

The radical anions and radical cations of the two tautomers (1e and 1i) of 5,10,15,20-tetraphenyl N-confused free-base porphyrin have been studied using a combination of cyclic voltammetry, steady state absorption spectroscopy, and computational chemistry. N-Confused porphyrins (NCPs), alternatively called 2-aza-21-carba-5,10,15,20-tetraphenylporphyrins or inverted porphyrins, are of great interest for their potential as building blocks in assemblies designed for artificial photosynthesis, and understanding the absorption spectra of the corresponding radical ions is paramount to future studies in multicomponent arrays where electron-transfer reactions are involved. NCP 1e was shown to oxidize at a potential of Eox 0.65 V vs Fc+|Fc in DMF and reduce at Ered −1.42 V, while the corresponding values for 1i in toluene were Eox 0.60 V and Ered −1.64 V. The geometries of these radical ions were computed at the B3LYP/6-31+G(d)//B3LYP/6-31G(d) level in the gas phase and in solution using the polarizable continuum model (PCM). From these structures and that of H2TPP and its corresponding radical ions, the computed redox potentials for 1e and 1i were calculated using the Born–Haber cycle. While the computed reduction potentials and electron affinities were in excellent agreement with the experimental reduction potentials, the calculated oxidation potentials displayed a somewhat less ideal relationship with experiment. The absorption spectra of the four radical ions were also measured experimentally, with radical cations 1e•+ and 1i•+ displaying significant changes in the Soret and Q-band regions as well as new low energy absorption bands in the near-IR region. The changes in the absorption spectra of radical anions 1e•- and 1i•- were not as dramatic, with the changes occurring only in the Soret and Q-band regions. These results were favorably modeled using time-dependent density functional calculations at the TD-B3LYP/6-31+G(d)//B3LYP/6-31G(d) level. These results were also compared to the existing data of free base tetraphenylporphyrin and free base tetraphenylchlorin.

Computational investigations into the ground and singlet excited-state structures and the experimental ground-state absorption spectra of N-confused tetraphenylporphyrin tautomers 1e and 1i and N-confused porphines (NCP) 2e and 2i have been performed. Structural data for the ground state, performed at the B3LYP/6-31G(d), B3LYP/6-31+G(d)//B3LYP/6-31G(d), and B3LYP/6-311+G(d)//B3LYP/6-31G(d) levels, are consistent with those performed at lower levels of theory. Calculations of the gas-phase, ground-state absorption spectrum are qualitatively consistent with condensed phase experiments for predicting the relative intensities of the Q(0,0) and Soret bands. Inclusion of implicit solvation in the calculations substantially improves the correlation of the energy of the Soret band with experiment for both tautomers (1e, 435 nm predicted, 442 nm observed in DMAc; 1i, 435 nm predicted, 437 nm observed in CH2Cl2). The x- and y-polarized Q-band transitions were qualitatively reproduced for 1e in both the gas phase and with solvation, although the low-energy absorption band in 1i was predicted at substantially higher energy (646 nm in the gas phase and 655 nm with solvation) than observed experimentally (724 nm in CH2Cl2). Franck−Condon state and equilibrated singlet excited-state geometries were calculated for unsubstituted NCP tautomers 2e and 2i at the TD-B3LYP/SVP and TD-B3LYP/TZVP//TD-B3LYP/SVP levels. Electronic difference density plots were calculated from these geometries, thereby indicating the change of electron density in the singlet excited states. Adiabatic S1 and S2 geometries of these compounds were also calculated at the TD-B3LYP/SVP level, and the results indicate that while 2i is a more stable ground-state molecule by ∼7.0 kcal mol−1, the energy difference for the S1 excited states is only ∼1.0 kcal mol−1 and is 6.1 kcal mol−1 for the S2 excited states.

A series of metallo Ru(II), Fe(II), Co(II) bisterpyridine polymers were prepared with naphthalene diimide (NDI) groups inserted between two 4′-phenyl-2,2:6′,2′′-terpyridine (phtpy) groups. Core-substituted NDIs typically have long-lived excited states with relatively high quantum yields, yet the NDI emission in these metallopolymers was completely quenched, most likely because of efficient electron-transfer from the M(phtpy)22+ groups to the excited NDIs. AFM, TEM and SEM experiments indicate that the regiochemistry of the substitution on the core of the naphthalene diimide, together with coordination of the terpyridine ligand to different metals, strongly influences the morphologies of the resulting metallosupramolecular polymers. The morphologies of spin-coated samples of the para-substituted polymers revealed the formation of long, bundled nanorods. Lengths on the order of ∼8 μm were observed for the bundle of the longest polymers (5-Ru) by both AFM and TEM microscopy. The morphologies of the meta substituted polymers, on the other hand, exhibited significantly shorter and less well-defined morphologies.