One dimensional (1D) Pt(II)-based metallo-supramolecular polymer with carboxylic acids (polyPtC) was synthesized using a new asymmetrical ditopic ligand with a pyridine moiety bearing two carboxylic acids. The carboxylic acids in the polymer successfully served as apohosts for imidazole loaded in the polymer interlayer scaffold to generate highly ordered 1D imidazole channels through the metallo-supramolecular polymer chains. The 1D structure of imidazole loaded polymer (polyPtC-Im) was analyzed in detail by thermogravimetric analysis, powder X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and ultraviolet–visible and photoluminescence spectroscopic measurements. PolyPtC-Im exhibited proton conductivity of 1.5 × 10–5 S cm–1 at 120 °C under completely anhydrous conditions, which is 6 orders of magnitude higher than that of the pristine metallo-supramolecular polymer.Keywords: anhydrous proton conductivity; imidazole; impedance; metallo-supramolecular polymer; platinum(II);

Two Ni(II)-based metallo-supramolecular polymers (polyNiL1 and polyNiL2) with different metal–metal distances were synthesized via (1 : 1) complexation between the Ni salts with bis(1,10-phenanthroline)s and their DNA binding properties and cytotoxicity were revealed. Short metal–metal distances (1.35 nm) in polyNiL2 showed ∼7 times stronger DNA binding properties and remarkably higher cytotoxicity to Hela-Fucci cells than long metal–metal distances (1.95 nm) in polyNiL1. Enhancement of Ni polymer-induced cell killing has been observed in a cell cycle study.

A unique type of gold nanocluster ligand was prepared for metallo-supramolecular polymer synthesis. The nanocluster was capped with mercapto-phenyl-terpyridine and supramolecular polymers were prepared by complexation with Fe(II) salt. The obtained polymers exhibited a porous structure with high ionic conductivity. The ionic conductivity was found to be more than an order of magnitude higher than the polymer without gold nanoclusters.

Linear Fe(II)-based metallo-supramolecular polymer chains were precisely aligned by the simple replacement of the counteranion with an N,N′-bis(4-benzosulfonic acid)perylene-3,4,9,10-tetracarboxylbisimide (PSA) dianion, which linked the polymer chains strongly. A parallel alignment of the polymer chains promoted by the PSA dianions yielded nanosheets formation. The nanosheets’ structure was analyzed with FESEM, HRTEM, UV–vis, and XRD in detail. The nanosheets showed more than 5 times higher proton conductivity than the original polymer due to the smooth ionic conduction through the aligned polymer chains. The complex impedance plot with two semicircles also suggested the presence of grain boundaries in the polymer nanosheets.

Water-soluble helical Fe(II)-based metallosupramolecular polymers ((P)- and (M)-polyFe) were synthesized by 1:1 complexation of Fe(II) ions and bis(terpyridine)s bearing a (R)- and (S)-BINOL spacer, respectively. The binding affinity to calf thymus DNA (ct-DNA) was investigated by titration measurements. (P)-PolyFe with the same helicity as B-DNA showed 40-fold higher binding activity (Kb = 13.08 × 107 M–1) to ct-DNA than (M)-polyFe. The differences in binding affinity were supported by electrochemical impedance spectroscopy analysis. The charge-transfer resistance (Rct) of (P)-polyFe increased from 2.5 to 3.9 kΩ upon DNA binding, while that of (M)-polyFe was nearly unchanged. These results indicate that ionically strong binding of (P)-polyFe to DNA chains decreased the mobility of ions in the conjugate. Unique rod-like images were obtained by atomic force microscopy measurement of the DNA conjugate with (P)-polyFe, likely because of the rigid binding between DNA chains and the polymer. Differences in polymer chirality lead to significantly different cytotoxicity levels in A549 cells. (P)-PolyFe showed higher binding affinity to B-DNA and much higher cytotoxicity than (M)-polyFe. The helicity in metallosupramolecular polymer chains was important not only for chiral recognition of DNA but also for coordination to a biological target in the cellular environment.

•Novel glucose oxidase immobilization matrix for glucose biosensor is described.•Efficient and precise glucose electrochemical detection is achieved.•The biosensor has good selectivity/stability, with ease of electrode preparation.A Co(II)-based metallo-supramolecular polymer (polyCo) was used as a novel matrix to immobilize glucose oxidase (GOx) for enzymatic glucose sensing. A facile fabrication of a modified glassy carbon electrode (GCE) was achievable by a one-step co-immobilization method. UV–vis spectroscopy and cyclic voltammetry were used to characterize the electrochemical biosensor and the sensing mechanism of the reaction on the polyCo-modified GCE. After the optimization of composition and loading of the polyCo/GOx GCE, the fabricated sensor demonstrated excellent amperometric quantification of glucose, with high sensitivity (47.1 μA mM−1 cm−2) in the linear range of up to 1.4 mM. The selectivity, based on the enzyme matrix without any pretreatment, was also sufficiently high. The outstanding stability of the sensor supported our assumption that metallo-supramolecular polymers can be used as electrode materials for glucose biosensors.

A Cd(II)-based metallo-supramolecular polymer (polyCd) was formed via the 1:1 complexation of Cd(II) ions with bis(1,10-phenanthroline) bearing a fluorine moiety as a luminescent spacer. The stepwise complexation was observed in UV-vis spectral titration. Selective sensing of Cd(II) ions based on the luminescent polymer formation was successfully achieved with sensitivity down to 8 nM concentration.

High proton conduction (8.5 × 10−2 mS cm−1) was observed in a Mo(VI)-based metallo-supramolecular polymer with carboxylic acids at 95%RH. The integration of OH groups into the polymer was analysed using FTIR spectroscopy and found to be crucial for the proton transport in the polymer.

Black-to-transmissive electrochromism has been obtained with a Co(II)-based metallo-supramolecular polymer (polyCo). Thin films of polyCo, based on bisterpyridine ligand assembled with Co(II) metal ion, were constructed by spray casting the polymer onto ITO glass. With such simple fabricating means to form good-quality films, polyCo films show stable switching at the central metal ion of the Co(II)/Co(I) redox reaction when immersed in aqueous solution. With an increase in the pH of the aqueous electrolyte solution from neutral, the film exhibits a color response due to the interaction between the d-orbital electron and hydroxide ions affecting the d–d* transition. As a result, a nearly transparent-to-black electrochromic performance can be achieved with a transmittance difference at 550 nm of 74.3% (81.9–7.6%) in pH 13 solution. The light absorption of the film can be tuned over light regions from visible to near-infrared with a large attenuation.Keywords: aqueous; bisterpyridine; cobalt; electrochromism; metallo-supramolecular polymer

In this study, electrochemical responses of inkjet-printed multicolored electrochromic devices (ECD) were studied to evaluate the feasibility of presenting multiple colors in one ECD. Metallo-supramolecular polymers (MEPE) solutions with two primary colors were inkjet-printed on flexible electrodes. By digitally controlling print dosages of each species, the colors of the printed EC thin film patterns can be adjusted directly without premixing or synthesizing new materials. The printed EC thin films were then laminated with a solid transparent thin film electrolyte and a transparent conductive thin film to form an ECD. After applying a dc voltage, the printed ECDs exhibited great contrast with a transmittance change (ΔT) of 40.1% and a high coloration efficiency of 445 cm2 C–1 within a short darkening time of 2 s. The flexible ECDs also showed the same darkening time of 2 s and still had a high ΔT of 30.1% under bending condition. This study demonstrated the feasibility to fabricate display devices with different color setups by an all-solution process and can be further extended to other types of displays.Keywords: electrochromic devices; flexible electronics; inkjet printing; metallo-supramolecular; multicolor patterning

A platinum(II)-based, luminescent, metallo-supramolecular polymer (PolyPtL1) having an inherent dipole moment was synthesized via complexation of Pt(II) ions with an asymmetric ligand L1, containing terpyridyl and pyridyl moieties. The synthesized ligand and polymer were well characterized by various NMR techniques, optical spectroscopy, and cyclic voltammetry studies. The morphological study by atomic force microscopy revealed the individual and assembled polymer chains of 1–4 nm height. The polymer was specifically attached on Au-electrodes to produce two types of film (films 1 and 2) in which the polymer chains were aligned with their dipoles in opposite directions. The Au-surface bounded films were characterized by UV–vis, Raman spectroscopy, cyclic voltammetry, and atomic force microscopy study. The quantum mechanical calculation determined the average dipole moment for each monomer unit in PolyPtL1 to be about 5.8 D. The precise surface derivatization permitted effective tuning of the direction dipole moment, as well as the direction of rectification of the resulting polymer-attached molecular diodes. Film 1 was more conductive in positive bias region with an average rectification ratio (RR = I(+4 V)/I(−4 V)) ≈ 20, whereas film 2 was more conducting in negative bias with an average rectification ratio (RR = I(−4 V)/I(+4 V)) ≈ 18.Keywords: Au-electrode; dipole moment; metallo-supramolecular polymer; platinum(II); rectification

Fe(II)-, Co(II)- and Ni(II)-based metallo-supramolecular polymers with three-dimensional (3D) hyperbranched structures (3D-polyFe, 3D-polyCo and 3D-polyNi) showed highly humidity-responsive ionic conductivity. The 3D polymers exhibited 10–100 times higher ionic conductivity than their 1D linear equivalents due to the improved ion conduction pathway in the amorphous 3D structure.

Metallo-supramolecular polymers, which were synthesized via the 1:1 complexation of metal ions with ditopic organic ligands, showed unique electro- and photo-chemical properties based on the metal–ligand or metal–metal interactions. Fe(II)-, Ru(II)- and Cu(II)-based metallo-supramolecular polymer films exhibited reversible electrochromic behaviour and electrochromic display devices were successfully fabricated. A polymer containing both Fe(II) and Ru(II) ions exhibited multi-colour electrochromic properties. Ionic conductivity of a Ni(II)-based polymer film was significantly enhanced with increasing humidity, and real-time humidity sensing was realized by utilizing the polymer film. A Eu(III)-based polymer showed vapoluminescence. Reversible switching of emission was achieved in the polymer with Fe(II) and Eu(III) ions introduced in an alternating manner.

Metallo-supramolecular polymers composed of Ni(II) ions and bis(2,9-dimethyl-1,10-phenanthroline) showed ionic conductivity, which enhanced by about four orders of magnitude with increasing relative humidity from 30 to 98% RH, in the film state. Four Ni(II)-based polymers with different counter anions were synthesized to investigate the ionic conduction mechanism. The highest ionic conductivity (5 × 10−2 S cm−1) at 98% RH was observed in the polymer with chloride ions as the counter anion. The Grotthuss-type proton transfer mechanism was indicated by the low activation energy (0.21 eV) for the ionic conduction. The polymer film prepared on an interdigitated electrode showed dynamic humidity-sensing properties based on the quick and large current-response to humidity change.

A series of Fe(II)-based metallo-supramolecular polymers with three-dimensional (3-D) structures were synthesized by the stepwise complexation of an Fe(II) salt with different ratios of a linear bis(terpyridine) ligand and a branched tris(terpyridine) ligand. Atomic force microscopy images of the polymer films showed a drastic change in the surface morphology upon varying the amount of the branched ligand. The surface of a designed 3-D construction film showed a highly porous structure (pore size: approximately 30–50 nm in diameter), probably due to the formation of a hyperbranched polymer structure. All the 3-D polymers had a blue color based on the metal-to-ligand charge-transfer (MLCT) absorption and exhibited excellent electrochromic properties. The most highly porous 3-D-structured film showed the best electrochromic performance; as compared with a 1-D linear polymer, the switching times were improved 38.7% for the coloring (0.31 → 0.19 s) and 37.9% for the bleaching (0.58 → 0.36 s). The transmittance change (ΔT) increased 21.8% (41.6 → 50.7%). Also, the coloration efficiency (η) was enhanced 45.3% (263.8 → 383.4 cm2 C–1). The redox in the 3-D film was diffusion-controlled, as supported by the linear relationship between the current and square root of the scan rate. It is considered that the porous structure of the 3-D polymer films contributed to smooth ionic transfer during the redox and to the improved electrochromic properties.Keywords: 3-D; coloration efficiency; electrochromism; metallo-supramolecular polymer; self-assembly;

Ni(II)-based metallo-supramolecular polymers (polyNiL1-4) were synthesized via complexation of Ni(II) ions with bis(1,10-phenanthroline) ligands bearing a different spacer and/or substituents. The ionic conductivity of the polymer films was greatly enhanced with increasing relative humidity. It was also found that the polymer without a hydrophobic spacer (polyNiL3) showed about 500 times as high ionic conductivity as the polymer with a spacer. The ionic conductivity of the polyNiL3 film reached 0.75 × 10−3 S cm−1 at 98%RH.

A series of Fe/Ru-based bimetallo-supramolecular polymers were synthesized by a stepwise coordination of Fe(II) and Ru(II) ions to bis(terpyridyl)benzene (L1). The polymers exhibited multi-colour electrochromic behaviour based on the redox potential of the metal ion. Electrochemical and electrochromic properties of the polymer films were analyzed in acetonitrile with 0.1 M lithium perchlorate as an electrolyte. The polymer films showed high optical contrast and very fast response times, demonstrated by transmittance changes (ΔT) at 508 and 585 nm that were 68% and 37%, respectively, within a few seconds. Coloration efficiencies (η) were established for the first time in a metallo-supramolecular electrochromic system, with values of 242.1 and 188.2 (cm2 C−1) at different wavelengths.

By utilizing different coordination properties of a lanthanide ion and a transition metal ion, a heterometallo-supramolecular polymer with Eu(III) and Fe(II) ions introduced alternately (polyEuFe) was precisely prepared via stepwise complexation of the metal ions to a new unsymmetrical ligand with both a dicarboxylate-substituted terpyridine and an unsubstituted terpyridine. The polymer showed unique, reversible “on–off” switching of the Eu(III) luminescence by electrochemical redox of the Fe ions in the solid-state.

A series of Zn(II)-based metallo-supramolecular polymers were prepared by 1:1 complexation of Zn(ClO4)2 and bis(terpyridine)s with electron-donating (alkoxy) or electron-withdrawing (cyano) groups at the 6-position of the peripheral pyridine moiety. The Zn(II)-based polymers displayed relatively high quantum yields (ΦPL = 0.68–0.76) in solution at room temperature. More importantly, they showed different luminescent colours of blue, cyan, and green in the film state, because of the large Stokes shift caused by the substituent effect of the ligand.

Co(III)- and Fe(III)-based metallosupramolecular polymers with aromatic azo ligands were synthesized via polycondensation of the diamino-substituted metal complexes with aromatic dialdehydes. Three different amino-substituted Co(III)-complexes were prepared through CN fusion reaction of [Co(pap)3](ClO4)2 with 1,4-phenylenediamine. All Co(III)- and Fe(III)-monomers and the metallosupramolecular polymers and a Co(III)-dimer were characterized by NMR, MS and UV–vis spectroscopy. Both the Co(III)- and Fe(III)-based metallosupramolecular polymers were electrochemically active and exhibited reversible electrochromism. The color of the Co(III)-based metallosupramolecular polymer could be changed upon application of an appropriate potential and regenerated upon reversal of the potential.Graphical abstract

Metallo-supramolecular polymers (RuL1, RuL2, RuL3, FeL3, and FeL4) prepared by complexation of bis(terpyridine) derivatives with Ru2+ or Fe2+ ions with octahedral coordination structures showed high binding ability to several DNAs (calf thymus DNA, herring sperm DNA, [poly(dA-dT)]2, and [poly(dG-dC)]2), which were revealed by UV–Vis absorption titration experiments. The electrostatic interactions between the metal cations of the polymers and phosphate anions of DNA led to formation of conjugate structure. The binding constant observed reached 3.7 × 107 M−1, which is the highest among values reported for metal complexes to date. Based on a long strand structure of the polymer, groove binding is most possible binding mode. Cell viability experiments showed that RuL3 and FeL3 displayed highly statistical significance (**p<0.01) to human non small cell lung cancer cell lines (NCI-H460).

An Eu-based metallo-supramolecular polymer (polyEu) was prepared by self-assembly coordination polymerization. Unique vapoluminescence property of polyEu triggered by acid–base vapor was found and a photoluminescence display in switchable imaging by acid–base vapor was fabricated.

Enantiopure phenylazomethine cages ((S)- and (R)-PAC) were selectively obtained by one-pot dehydration of chiral (S)- and (R)-syn-tris(norborneno)benzene with p-phenylenediamine in moderate yields (56% and 50%), respectively. The structure and chirality of PACs in solution and solid state were confirmed by NMR, CD, X-ray diffraction and DFT calculations.

We have fabricated a unique memristive device by molecular engineering and demonstrated that the leakage current tuning in the device is 100 times more efficient than that in a standard device. Molecular analogs of the memristive matrices used here are an electrochemically active conjugated Co(III) polymer (CP) and a nonconjugated Co(III) polymer (NCP), which have been synthesized in good yield and characterized by 1H NMR spectroscopy. Redox switching of an organic−metallic hybrid polymer generates bistable states with a large ON/OFF ratio that supports random flip-flops for several hours. Thus, we provide a synthetic solution to leakage current restriction, one of the fundamental problems faced when fabricating state-of-the-art electronic devices.

Strong electrostatic interaction between metallo-supramolecular polymers and DNA was confirmed by UV-vis and CD spectral measurements during titration, and cyclic voltammetry. The stable conjugation structure based on groove binding was revealed by using QM/MM computational methodology and supported by AFM.

New gold nanoparticles covered with cyclic phenylazomethine (CPA) were obtained by a one-pot synthesis. It is confirmed by XPS that imines of CPA in the nanoparticles (Au-CPA) are partially reduced to amines. The amine part of CPA in Au-CPA is attached to the surfaces of gold nanoparticles, and the imine part works as a redox-active site. A glassy carbon electrode modified with Au-CPA was revealed to work as an electrochemical probe for metal ion sensing.

Dimethyl-substituted bis-terpyridines (L1 and L2) are synthesized as novel ditopic ligand through aldol condensation, Michael-type bis-addition and Suzuki-type cross-coupling. Metallo-supramolecular coordination polymers are obtained by complexation of the bis-terpyridines with metal ions [Ru(II), Fe(II), Co(II)] in suitable solvent. The complexation ratio (1:1) of the ligand with the metal ion in the coordination polymer is confirmed by UV–vis titration experiments and Job’s plot analysis. The binding constants (logK) in the complexation are very high (>9) and the results show that steric hindrance by the methyl groups of the ligand can be ignored in the polymer formation. Their optical, photophysical and electrochemical properties are characterized by UV–vis, luminescence measurements and cyclic voltammetry, respectively, and the substituent effects are discussed. Especially, the luminescence of the Ru(II) polymers is quenched by introduction of the methyl group to bis-terpyridine. Molecular weights of the polymers are estimated by SEC-viscometry-RALS method.

The optically active metallo-supramolecular polymers were successfully synthesized via complexation of Fe(II) ions with new bis-terpyridines containing chiral tetra-ethylene glycol units at the ortho-position of the peripheral pyridine rings. In addition, we also revealed solvent and temperature effects toward assembly and dis-assembly behavior of polymers.

Organic-metallic hybrid polymers are formed by the complexation of metal ions with organic modules bearing two coordination sites. The hybrid polymers consisting of bis-terpyridines and metal ions such as Fe(II) or Ru(II) have a specific color based on the metal-to-ligand charge transfer (MLCT) absorption. Cyclic voltammograms of the polymers exhibit a reversible redox wave according to the redox reaction of the metal ions. Interestingly, a polymer film cast on an indium tin oxide (ITO) electrode exhibits excellent electrochromic properties; the color of the film disappears when a higher potential as compares to the redox potential of the metal ions is applied to the polymer film. In addition, multicolor electrochromic changes appear on introducing two types of metal ions to the polymer. Electrochromic solid-state devices are successfully fabricated by using these polymers.

We present the study of photophysical properties of several Ru(II)-based metallo-supramolecular coordination polymers (MEPEs) constructed from various ditopic bis-terpyridines (bis-tpy) bearing electron-rich (OMe) or electron-deficient (Br) groups at the 6-position of the pyridyl periphery and having different spacers for connecting the two tpy moieties. The MEPEs are distinct from the frequently reported analogues derived from unsubstituted tpy. The photophysical properties such as emission spectroscopic properties and lifetime at both room temperature and 77 K are presented. The MEPEs are luminescent at room temperature with quantum yields (Φlum) < 10−6 and lifetimes on a timescale of nanoseconds (τ = ca. 6.6–22.4 ns), and display strong luminescence at 77 K with Φlum = ca. 0.21–2.5 × 10−2 and lifetimes on a timescale of microseconds (τ = ca. 2.4–7.9 μs). More importantly, we find that introduction of either an electron-rich or an electron-deficient functional group at the 6-position of the ligands results in a clearly decreased absorption intensity of the derived MEPEs. This result is in contrast to the reported data in the literature where an increased intensity was observed when substitution occurred at the 4′-position of tpys, regardless of the electron-rich or electron-deficient nature of the substituents. In accordance with the absorption behaviour, substitution at the 6-position also leads to a notably different effect on the luminescent properties of the complexes. Thus, our results provide an alternative strategy for the de novo design of new materials.

As novel organic modules in organic–metallic hybrid materials, we synthesized bromo-substituted bis-terpyridines and cyclic phenylazomethine. Bromo-substituted bis-terpyridines were prepared via condensation of aromatic dienones with bromo-substituted pyridinium salt in the presence of ammonium acetate. On the other hand, cyclic phenylazomethine was obtained during dehydration of an aromatic amine with an aromatic ketone in the presence of titanium tetrachloride as a Lewis acid. Since these organic modules have multi-coordination sites and high coordination ability for metal ions such as iron and cobalt ions, organic–metallic hybrid materials were formed by complexation of these organic modules with metal ions. Electrochemical properties of the hybrid materials were investigated using cyclic voltammetry.

A rich variety of novel ditopic bis-terpyridines, by symmetric and unsymmetric introduction of functional groups in the pyridine rings, as well as tuning the spacers for bridging the two terpyridine moieties, is described. These bis-terpyridines are useful ligands for developing new metallo-supramolecular materials with novel functions, as well as for investigating the structure–property relationships. In order to investigate the structural factors of bis-terpyridine based metallo-supramolecular materials, such as the functional groups in the ring periphery of the ligands and the spacers between the two terpyridine coordination components, several different types of CoII-bis-terpyridine supramolecular polymers were prepared from various bis-terpyridine functional modules and Co(OAc)2. The absorption and the electrochemical behavior of these new supramolecular polymers were studied by UV/Vis spectroscopy and differential pulse voltammetry (DPV), respectively. The results showed that the introduction of electron donating groups at the pyridine ring affects remarkably the charge transfer and electrochemical properties of the coordination polymers. In addition, the electrochromic properties of the coordination polymers were also studied. Significant color change and high reversibility were observed from these polymers.

Poly(phenylazomethine) derivatives are interesting compounds as “functional modules” in organic-metallic hybrid nano-materials. We synthesized oligo(phenylazomethine)s (OPAs), the aniline-capped OPAs (OPA's), and dendritic poly(phenylazomethine)s (DPAs) via dehydration of aromatic amines with aromatic ketones in the presence of TiCl4. DPA derivatives having tris(thienylphenyl)amine and tetraphenylporphyrin as the core (TPA-DPAs and Por-DPAs) and aniline-capped DPAs were obtained during the dehydration of the DPA dendrons with tris(4-aminothienylphenyl)amine, tetra(4-aminophenyl)porphyrin, and aniline, respectively. Stepwise radial complexation with SnCl2 in DPAs, TPA-DPAs, Por-DPAs, and aniline-capped DPAs, was found as stepwise shifts of the isosbestic point during the UV–vis spectroscopic observation. The coordination constants of four kinds of imines in the aniline-capped DPA G4 with trifluoroacetic acid were determined.

Heterometallo-supramolecular polymers with Pt(II) and Fe(II) ions introduced alternately (cis-polyPtFe and trans-polyPtFe) in a precise way were prepared successfully by the 1:1 complexation of Fe(II) ions with cis- or trans-conformational organo-Pt(II) ligands. The conformational difference between cis- and trans-greatly changed the morphology, crystallinity, ionic conductivity, electrochromic properties, and redox-triggered fluorescence of the polymers. The cis-polyPtFe exhibited better crystallinity and low ionic conductivity, whereas trans-polyPtFe showed an amorphous nature with high ionic conductivity. Both the polymers exhibited reversible electrochromism between purple and yellow colors due to the redox of Fe(II)/(III) upon applying a potential of 0 V or +3 V. The trans-polyPtFe showed better electrochromic stability and response times compared to cis-polyPtFe. In addition, the trans-polyPtFe also showed an improved response in redox-triggered Raman scattering switching compared to cis-polyPtFe over a long time range.

An Eu-based metallo-supramolecular polymer (polyEu) was prepared by self-assembly coordination polymerization. Unique vapoluminescence property of polyEu triggered by acid–base vapor was found and a photoluminescence display in switchable imaging by acid–base vapor was fabricated.

A Cd(II)-based metallo-supramolecular polymer (polyCd) was formed via the 1:1 complexation of Cd(II) ions with bis(1,10-phenanthroline) bearing a fluorine moiety as a luminescent spacer. The stepwise complexation was observed in UV-vis spectral titration. Selective sensing of Cd(II) ions based on the luminescent polymer formation was successfully achieved with sensitivity down to 8 nM concentration.

Strong electrostatic interaction between metallo-supramolecular polymers and DNA was confirmed by UV-vis and CD spectral measurements during titration, and cyclic voltammetry. The stable conjugation structure based on groove binding was revealed by using QM/MM computational methodology and supported by AFM.

We present the study of photophysical properties of several Ru(II)-based metallo-supramolecular coordination polymers (MEPEs) constructed from various ditopic bis-terpyridines (bis-tpy) bearing electron-rich (OMe) or electron-deficient (Br) groups at the 6-position of the pyridyl periphery and having different spacers for connecting the two tpy moieties. The MEPEs are distinct from the frequently reported analogues derived from unsubstituted tpy. The photophysical properties such as emission spectroscopic properties and lifetime at both room temperature and 77 K are presented. The MEPEs are luminescent at room temperature with quantum yields (Φlum) < 10−6 and lifetimes on a timescale of nanoseconds (τ = ca. 6.6–22.4 ns), and display strong luminescence at 77 K with Φlum = ca. 0.21–2.5 × 10−2 and lifetimes on a timescale of microseconds (τ = ca. 2.4–7.9 μs). More importantly, we find that introduction of either an electron-rich or an electron-deficient functional group at the 6-position of the ligands results in a clearly decreased absorption intensity of the derived MEPEs. This result is in contrast to the reported data in the literature where an increased intensity was observed when substitution occurred at the 4′-position of tpys, regardless of the electron-rich or electron-deficient nature of the substituents. In accordance with the absorption behaviour, substitution at the 6-position also leads to a notably different effect on the luminescent properties of the complexes. Thus, our results provide an alternative strategy for the de novo design of new materials.

A series of Fe/Ru-based bimetallo-supramolecular polymers were synthesized by a stepwise coordination of Fe(II) and Ru(II) ions to bis(terpyridyl)benzene (L1). The polymers exhibited multi-colour electrochromic behaviour based on the redox potential of the metal ion. Electrochemical and electrochromic properties of the polymer films were analyzed in acetonitrile with 0.1 M lithium perchlorate as an electrolyte. The polymer films showed high optical contrast and very fast response times, demonstrated by transmittance changes (ΔT) at 508 and 585 nm that were 68% and 37%, respectively, within a few seconds. Coloration efficiencies (η) were established for the first time in a metallo-supramolecular electrochromic system, with values of 242.1 and 188.2 (cm2 C−1) at different wavelengths.

Metallo-supramolecular polymers, which were synthesized via the 1:1 complexation of metal ions with ditopic organic ligands, showed unique electro- and photo-chemical properties based on the metal–ligand or metal–metal interactions. Fe(II)-, Ru(II)- and Cu(II)-based metallo-supramolecular polymer films exhibited reversible electrochromic behaviour and electrochromic display devices were successfully fabricated. A polymer containing both Fe(II) and Ru(II) ions exhibited multi-colour electrochromic properties. Ionic conductivity of a Ni(II)-based polymer film was significantly enhanced with increasing humidity, and real-time humidity sensing was realized by utilizing the polymer film. A Eu(III)-based polymer showed vapoluminescence. Reversible switching of emission was achieved in the polymer with Fe(II) and Eu(III) ions introduced in an alternating manner.

Ni(II)-based metallo-supramolecular polymers (polyNiL1-4) were synthesized via complexation of Ni(II) ions with bis(1,10-phenanthroline) ligands bearing a different spacer and/or substituents. The ionic conductivity of the polymer films was greatly enhanced with increasing relative humidity. It was also found that the polymer without a hydrophobic spacer (polyNiL3) showed about 500 times as high ionic conductivity as the polymer with a spacer. The ionic conductivity of the polyNiL3 film reached 0.75 × 10−3 S cm−1 at 98%RH.

Metallo-supramolecular polymers composed of Ni(II) ions and bis(2,9-dimethyl-1,10-phenanthroline) showed ionic conductivity, which enhanced by about four orders of magnitude with increasing relative humidity from 30 to 98% RH, in the film state. Four Ni(II)-based polymers with different counter anions were synthesized to investigate the ionic conduction mechanism. The highest ionic conductivity (5 × 10−2 S cm−1) at 98% RH was observed in the polymer with chloride ions as the counter anion. The Grotthuss-type proton transfer mechanism was indicated by the low activation energy (0.21 eV) for the ionic conduction. The polymer film prepared on an interdigitated electrode showed dynamic humidity-sensing properties based on the quick and large current-response to humidity change.

A unique type of gold nanocluster ligand was prepared for metallo-supramolecular polymer synthesis. The nanocluster was capped with mercapto-phenyl-terpyridine and supramolecular polymers were prepared by complexation with Fe(II) salt. The obtained polymers exhibited a porous structure with high ionic conductivity. The ionic conductivity was found to be more than an order of magnitude higher than the polymer without gold nanoclusters.

A series of Zn(II)-based metallo-supramolecular polymers were prepared by 1:1 complexation of Zn(ClO4)2 and bis(terpyridine)s with electron-donating (alkoxy) or electron-withdrawing (cyano) groups at the 6-position of the peripheral pyridine moiety. The Zn(II)-based polymers displayed relatively high quantum yields (ΦPL = 0.68–0.76) in solution at room temperature. More importantly, they showed different luminescent colours of blue, cyan, and green in the film state, because of the large Stokes shift caused by the substituent effect of the ligand.

By utilizing different coordination properties of a lanthanide ion and a transition metal ion, a heterometallo-supramolecular polymer with Eu(III) and Fe(II) ions introduced alternately (polyEuFe) was precisely prepared via stepwise complexation of the metal ions to a new unsymmetrical ligand with both a dicarboxylate-substituted terpyridine and an unsubstituted terpyridine. The polymer showed unique, reversible “on–off” switching of the Eu(III) luminescence by electrochemical redox of the Fe ions in the solid-state.

High proton conduction (8.5 × 10−2 mS cm−1) was observed in a Mo(VI)-based metallo-supramolecular polymer with carboxylic acids at 95%RH. The integration of OH groups into the polymer was analysed using FTIR spectroscopy and found to be crucial for the proton transport in the polymer.

A fluorescent dye anion (sulforhodamine B, SRB) was successfully introduced into a Fe(II)-based metallo-supramolecular polymer (polyFe) by exchanging the counter anion. The exchange was confirmed by elemental analysis, UV-vis absorption spectroscopy, 1H-NMR spectroscopy, and FTIR spectroscopy. A solid-state device using the obtained polymer (polyFe–SRB) shows electrochromic properties based on the electrochemical redox of Fe(II) ions by applying ±2.8 V. The device shows electrochemical switching of photoluminescence at 584 nm by applying ±2.8 V. This switching was caused by the appearance and disappearance of the metal-to-ligand charge transfer (MLCT) absorption of polyFe–SRB. It is considered that the MLCT absorbs the excitation light at 560 nm or the emission from SRB.