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A light-on sensor that could detect N-heteroaromatic vapour by luminescence was fabricated using a coordinatively unsaturated Cu(I) complex [CuI(xantphos)] (xantphos = 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene, Cu-x). The vapoluminescent thin film, Cu-x@PVP was prepared using Cu-x and polyvinylpyrrolidone (PVP) via spin-coating. When the hardly emissive film was exposed to pyridine (py) vapour, it emitted bright blue-green luminescence immediately (≦15 s), while on exposure to 2-methylpyrazine (Mepyz), yellow emission occurred. By taking up vapour molecules, four-coordinate Cu(I) complexes with intense luminescence originating from thermally activated delayed fluorescence (TADF) are rapidly produced, as evidenced from both spectroscopy and computational studies. The unsaturated structure of Cu-x enabled a rapid response to vapour based on the ligand addition reaction compared to previous vapochromic Cu(I) complex systems based on the ligand-exchange reaction. Cu-x@PVP was easily recovered by the release of vapour molecules in the air, indicating a reversible vapochromic behaviour. X-ray diffraction measurements indicated a reversible transformation from the triangular Cu-x to the tetrahedral species [CuI(L)(xantphos)] (Cu-x–L; L = py, Mepyz) by the coordination/dissociation of the N-heteroaromatic vapour molecules. The efficient vapour response for the thin film was confirmed compared with that of the bulk powder: The apparent rate constant to the vapochromic response, kobs, was estimated to be 3 × 10−2 s−1 for Cu-x@PVP based on the emission intensity evolution by the Mepyz vapour, which was approximately six times larger than that of the Cu-x powder sample (kobs = 5 × 10−3 s−1). The results demonstrate that the utilisation of the coordinatively unsaturated Cu(I) complex provides a promising strategy for the easy sensing of toxic vapours, such as N-heteroaromatics. [ABSTRACT FROM AUTHOR]

A coordination polymer, [Cu(SCN)(iqi)]n (iqi = isoquinoline), containing copper(I) thiocyanate and a nitrogen-containing π-conjugated ligand, iqi, has been synthesized and its physical properties were evaluated. This coordination polymer has a two-dimensional (2D) sheet structure consisting of copper(I) thiocyanate and shows photoluminescence derived from 3MLCT and photoconductive properties. [ABSTRACT FROM AUTHOR]

Molecular crystals of Pt(II) complexes with metallophilic interactions can provide bright assembly-induced luminescence with colour tunability. However, the brittleness of many of these crystals makes their application in flexible optical materials difficult. Herein, we have achieved the elastic deformation of crystals of polyhalogenated Pt(II) complexes exhibiting bright assembly-induced luminescence. A crystal of [Pt(bpic)(dFppy)] (Hbpic = 5-bromopicolinic acid, HdFppy = 2-(2,4-difluorophenyl)pyridine) and a co-crystal of [Pt(bpic)(dFppy)] and [Pt(bpic)(ppy)] (Hppy = 2-phenylpyridine) were found to exhibit significant elastic deformation due to their highly anisotropic interaction topologies. While the crystal of [Pt(bpic)(dFppy)] exhibited monomer-based ligand-centred 3ππ* emission with an emission quantum yield of 0.40, the co-crystal exhibited bright, triplet metal–metal-to-ligand charge transfer (3MMLCT) emission owing to Pt⋯Pt interactions, thereby achieving a significantly higher emission quantum yield of 0.94. [ABSTRACT FROM AUTHOR]

A series of Pt(II) complexes bearing N-heterocyclic carbenes, [Pt(CN)2(Rim-Mepy)] (Rim-MepyH+ = 3-alkyl-1-(4-methyl-(2-pyridinyl))-1H-imidazolium, R = Me, Et, iPr, or tBu), exhibits triboluminescence in the visible range from blue to red, as well as the corresponding intense photoluminescence. Remarkably, among the complexes, the iPr-substituted one exhibits chromic triboluminescence behaviour during the process of rubbing and also vapour exposure. [ABSTRACT FROM AUTHOR]

We synthesized new oxygen-evolving molecular Ru(II) catalysts with one or two carbazole moieties on the axial pyridyl ligands, namely [Ru(bda)(cbz-py)(py)] and [Ru(bda)(cbz-py)2] [C1 and C2; bdaH2 = 2,2′-bipyridyl-6,6′-dicarboxylic acid, py = pyridine, and cbz-py = 9-(pyridin-4-yl)-9H-carbazole] to investigate the effect of cbz modification on the photophysical and catalytic properties of the well-known molecular catalyst [Ru(bda)(py)2] (C0). The initial oxygen-evolving catalytic activities of C1 and C2 were higher than that of C0 in both a chemical reaction driven by the strong oxidant (NH4)2[Ce(NO3)6] (CAN = ceric ammonium nitrate) and photochemical oxidation using a [Ru(bpy)3]2+ (bpy = 2,2′-bipyridine) photosensitizer with Na2S2O8 as the sacrificial oxidant. The higher activities were ascribed to the electron-withdrawing cbz groups, which promoted the radical coupling reaction to form a RuIV–O–O–RuIV species. A unique oxygen-evolution rate change behaviour was observed for both C1 and C2 in the presence of a large excess of CAN, suggesting the competitive oxidation of the cbz moiety during the chemical oxygen evolution reaction. This work suggests that the cbz modification of an oxygen evolution molecular catalyst is a promising approach for integrating the hole accumulator near the oxygen evolution catalytic centre. [ABSTRACT FROM AUTHOR]

Single crystals showing elastic flexibility have attracted increasing attention as next-generation soft materials. Herein, we successfully developed a series of polyhalogenated platinum(II)–bipyridine complexes showing solvent-of-crystallisation-dependent elastic flexibility. Notably, methanol-solvated crystals were the first examples of flexible crystals showing assembly-induced luminescence arising from the triplet metal–metal-to-ligand charge transfer (3MMLCT) excited state. Furthermore, factors inducing elastic deformability based on the packing structures of the crystals were explored. [ABSTRACT FROM AUTHOR]

The luminescent and proton conductive Pt(II) complex [PtCl(tpy-o-py)]Cl and its HCl adduct [PtCl(tpy-o-pyH)]Cl2 (o-Pt and o-Pt·HCl , respectively; tpy-o-py = 2,2′:6′,2′′-terpyridine-6′,2′′′-pyridine) were synthesised and their crystal structures, vapochromic behaviour, and proton conduction, were investigated and compared to those of the para isomers [PtCl(tpy-p-py)]Cl and [PtCl(tpy-p-pyH)]Cl2 (p-Pt and p-Pt·HCl , respectively; tpy-p-py = 2,2′:6′,2′′-terpyridine-4′,4′′′-pyridine). X-ray structure analysis revealed that the intermolecular metallophilic (Pt⋯Pt) interaction was negligible in o-Pt but effective in o-Pt·HCl. Reversible transformation between o-Pt and o-Pt·HCl coupled with significant colour and luminescence changes was achieved by four different external stimuli, namely: exposure of o-Pt to humid HCl gas to form o-Pt·HCl , heating, exposure to MeOH vapour, and finally drying in air to regenerate the original o-Pt. The intraligand π–π* orange emission observed for o-Pt exhibited negligible dependence on the relative humidity (RH). Conversely, o-Pt·HCl exhibited red metal–metal-to-ligand charge-transfer (MMLCT) phosphorescence at 725 nm, originating from effective intermolecular Pt–Pt interactions, and interesting vapochromic behaviour that was dependent on the RH. Notably, o-Pt·HCl presented higher conductivity than the p-Pt·HCl isomer at RH < 80%. This trend was reversed at RH values > 80%, probably owing to the second water-adsorption-induced transformation of p-Pt·HCl. The cooperative phenomenon between the proton conduction and vapochromic behaviour observed for both o-Pt·HCl and p-Pt·HCl should allow the visualisation of the proton-conducting pathway, without the need for a bulk electrode, via the absorption and emission colours at both macroscopic and microscopic levels. [ABSTRACT FROM AUTHOR]

A homogeneous thin film of a simple and highly luminescent Cu(I) complex, [CuI(PPh3)2(py)] (PPh3 = triphenylphosphine, py = pyridine) (Cu–py), was fabricated via spin coating using polyvinylpyrrolidone (PVP) and pyridine without destroying the complex. The thin film (Cu–py@PVP), with a thickness of 1 μm, exhibited efficient response to vapour, exhibiting reversible luminescence changes between blue-green and yellow upon exposure to vapours of N-heteroaromatic compounds such as py and 2-methylpyrazine (Mepyz). Vapochromic luminescence colour change resulting from ligand substitution was also observed in the crystal state, but the response of the thin film was remarkably faster than that of the crystalline samples. The vapour-induced ligand exchange on the thin film was fully characterised by comparing the luminescence properties of the Cu–py crystal with the newly prepared Cu(I) complex, [CuI(Mepyz)(PPh3)2] (Cu–Mepyz). [ABSTRACT FROM AUTHOR]

Porous molecular crystals (PMCs) should function as new-generation functional porous materials, but the selective crystallisation of PMCs is still difficult. Herein we demonstrate that the liquid–liquid interface between the MeOH/H2O mixture and alkanes promotes the crystallisation of a Pt(II)-based PMC, rather than the nonporous form. This new crystallisation method allows control of not only the porosity but also the luminescence of the Pt(II) complex crystal. [ABSTRACT FROM AUTHOR]

Recently, non-crystalline coordination materials have been shown to represent a versatile class of functional materials. However, such materials incorporating metal complex clusters have remained largely unexplored. Herein, we demonstrate that a luminescent tetranuclear ReV cluster melts at 489 K, with the cluster structure being maintained in the corresponding supercooled ionic liquid phase. [ABSTRACT FROM AUTHOR]

Controlled generation of homoleptic versus heteroleptic Au I2 M (M = NiII, ZnII) trinuclear complexes, which is achieved by a slight change in the diphosphine P^P linker of digold(I) metalloligands, [Au2(P^P)(D -pen)2]2− (L1P^P; D -pen = D -penicillaminate) and [Au2(P^P)(L -cys)2]2− (L2P^P; L -cys = L -cysteinate), is reported. The reactions of a 1 : 1 mixture of L1dppm and L2dppm (dppm = bis(diphenylphosphino)methane) with M = NiII, ZnII gave the homoleptic Au I2 M complexes, [M(L1dppm)] and [M(L2dppm)], which co-crystallized to form [M(L1dppm)]·[M(L2dppm)] (1M). Similar reactions using L1dppe and L2dppe (dppe = bis(diphenylphosphino)ethane), instead of L1dppm and L2dppm, led to the selective production and crystallization of the heteroleptic Au I2 M complex, [M(L3dppe)] (2M; L3dppe = [Au2(dppe)(L -cys)(D -pen)]2−), accompanied by the scrambling of L1dppe and L2dppe. The homoleptic 1M and the heteroleptic 2M showed different absorption (green versus blue) and emission (yellow versus orange) colours for M = NiII and ZnII, respectively. [ABSTRACT FROM AUTHOR]

In this study, we discovered a method to synthesize large single crystals of Cu-BTC MOFs (Cu-s) with the assistance of a surfactant (PF-127) in an ethanol–water mixture solution. Single crystal and powder XRD (X-ray diffraction) measurements revealed that Cu-s, with the appearance of long rods, has the chemical formula Cu(BTC)3·H2O. We proposed the growth mechanism of Cu-s by a series of experiments and demonstrated that the addition of surfactant PF-127 can effectively inhibit the contact between Cu2+ ions and BTC ligands, which favoured the growth of Cu-s along the a-axis and suppressed the fast formation of porous Cu-BTC MOFs (HKUST-1). Considering that the photoactive properties of Cu-s and its relatively large size (an average length of up to ∼3 mm), we constructed a simple photo-detector device, showing excellent photo-sensing properties under illumination. [ABSTRACT FROM AUTHOR]

Luminescent ionic liquids, based on anionic Pt(ii) complexes, were developed. Depending on the cyclometalating ligands used, they exhibit thermochromic luminescence with different colours. The chromic properties in the flexible liquid and glass states emerge through the self-assembling character of the square-planar Pt(ii) complexes. [ABSTRACT FROM AUTHOR]

A luminescent Pt(ii) complex [Pt(CN)2(H4dpbpy)] (1P; H4dpbpy = 2,2′-bipyridine-4,4′-diphosphonic acid) bearing a phosphonic-acid-functionalized bipyridine ligand was successfully synthesized and its unique two-way vapochromic behaviour investigated. X-ray structure analyses of both the anhydrous 1P and penta-hydrated 1P·5H2O phases clearly reveal the activation of intermolecular Pt…Pt interactions through the adsorption of water vapour. Emission spectroscopy reveals that the penta-hydrated 1P·5H2O complex exhibits an orange emission at 585 nm that shifts in two directions, to a blue-green emission at 469 nm by drying at 100 °C or to a red emission at 701 nm by drying under vacuum at room temperature. Thermogravimetric analyses and powder X-ray diffraction studies clearly reveal that anhydrous 1P, with negligible intermolecular Pt…Pt interactions, is formed by drying at 100 °C whereas the monohydrate 1P·H2O phase, with effective Pt…Pt interactions, is formed by drying under vacuum. [ABSTRACT FROM AUTHOR]

[CuCl(PPh3)2(4-Mepy)] (PPh3 = triphenylphosphine, 4-Mepy = 4-methylpyridine), a highly blue-luminescent mononuclear copper(i) complex, shows reversible emission colour change ranging from blue-green to red by vapour exposure to N-heteroaromatics, such as pyridine, pyrimidine, and 2-methylpyrazine. The remarkable colour changes occur due the ligand exchange reaction between the solid and gas. Such ligand exchange reactions would be applicable to various vapours with coordination ability and be useful for the sensing of such volatile organic compounds as well as a new convenient methodology for the preparation of luminescent complexes. [ABSTRACT FROM AUTHOR]

The stepwise reaction of a zwitterionic ligand, 4-methylamino-6-methyliminio-3-oxocyclohexa-1,4-dien-1-olate (QH2) with [Pt2(μ-Cl)2(ppy)2] (Hppy = 2-phenylpyridine) afforded a mononuclear complex, [Pt(ppy)(QH)] (1), and a dinuclear complex, [{Pt(ppy)}2(μ-Q)] (2). Using [Pd2(μ-Cl)2(ppy)2] in the second step resulted in the formation of a heterodinuclear complex, [{Pt(ppy)}(μ-Q){Pd(ppy)}] (3), which is the first heterodinuclear complex bridged by a quinonoid ligand. Single crystal X-ray diffraction analysis revealed that all three complexes adopted double-decker structures in the crystal. For 1, intermolecular N–H…O interactions between uncoordinated N–H and O groups in two adjacent square-planar mononuclear units led to the formation of hydrogen-bonded dimers, which stacked to form a herringbone structure with a double-decker tetranuclear motif. For 2 and 3, dinuclear units bridged by Q2− formed a double-decker motif similar to that of 1, but a tetranuclear chain in the herringbone pattern was characteristic of the dinuclear complexes. Pt…Pt (or Pt…Pd) distances were more than 3.5 Å, twice the van der Waals radii of Pt, suggesting weak electronic metal–metal interactions in the crystal structures. Thus, the different colours observed (brown, purple, and dark green for 1, 2, and 3, respectively) mainly originated from the molecular structures. In fact, the three complexes exhibited colourful solutions of yellow, red, and green. UV-vis absorption spectroscopy and time-dependent density-functional theory (TD-DFT) calculations revealed that colour variations occurred depending on the electronic states composed of metal ions and the quinonoid ligand. [ABSTRACT FROM AUTHOR]

The redox-active metalloligand (RML) (Et3NH)3[CrIII(F4Cat)3] (F4Cat = perfluorocatecholato) (1) was synthesized and its interactions with guest metal ions Li+, Mn2+, Fe2+, Co2+, Cu2+, and Zn2+ were examined. Cyclic voltammetry measurements and spectroelectrochemical studies revealed that complex 1 shows three-step ligand-centred one-electron oxidation to consecutively generate [CrIII(F4Cat)2(F4SQ)]2− (F4SQ = perfluorosemiquinonato), [CrIII(F4Cat)(F4SQ)2]−, and [CrIII(F4SQ)3] at −0.12, 0.23, and 0.53 V vs. Ag/Ag+ in dichloromethane, or at −0.21, 0.08, and 0.50 V in acetonitrile (MeCN), respectively. Titration experiments in MeCN revealed that treatment of 1 with Cu2+ leads to the formation of [CrIII(F4Cat)2(F4SQ)]2− and Cu+via a redox reaction. However, when 1 was treated with Li+, Mn2+, Fe2+, Co2+, and Zn2+, further titration experiments revealed that these metal ions coordinated via the lone pairs on the coordinating oxygen atoms of the F4Cat2− moieties in a one-to-one ratio, and binding constants of 3.7 (±0.3) × 104 (Li+), 1.5 (±0.2) × 105 (Mn2+), 2.2 (±0.4) × 105 (Fe2+), 1.9 (±0.2) × 105 (Co2+), and 3.8 (±0.4) × 105 M−1 (Zn2+) were established. Moreover, the oxidation potentials of 1 were positively shifted by 0.08–0.33 V upon addition of guest metal ions. Spectroelectrochemical studies of 1 in the presence of guest metal ions suggested that ligand-centred one- and two-electron oxidation of the RML occurred for Li+, Mn2+, Co2+, and Zn2+, respectively, while guest metal-centred one-electron oxidation was observed for Fe2+. Considering all the aforementioned results, this study demonstrated for the first time the ability of [CrIII(F4Cat)3]3− to act as a RML in solution. [ABSTRACT FROM AUTHOR]

The introduction of a Au(iii) ion into a mesogenic core, [M(Bdt)(Cnbpy)]+ (Bdt = 1,2-benzenedithiolato and Cnbpy = 4,4′-di-alkyl-2,2′-bipyridine (n = 13 (4,4′-di-tridecyl-2,2′-bipyridine (C13bpy)) and 8,10 (4,4′-di-(3-octyltridecyl)-2,2′-bipyridine (C8,10bpy)))), leads to the formation of ionic molecular assemblies in crystalline and mesophases. Successive syntheses of precursor complexes, [AuCl2(Cnbpy)]PF6 (n = 13 (1) and 8,10 (2)), followed by the target complexes, [Au(Bdt)(Cnbpy)]PF6 (n = 13 (3) and 8,10 (4)), were achieved. The crystallographic analysis of 3 revealed that the central cationic cores form a characteristic one-dimensional columnar structure, which is an essential property for the formation of columnar structures in the liquid crystalline phase. The central cores of the [Au(Bdt)(C13bpy)]+ cations in 3 stack alternatively so as to cancel out their dipole moments and the counteranions lie between the cationic columns. Furthermore, the introduction of the branched alkyl tails in 4 induces the formation of a rectangular columnar liquid crystalline phase (Colr) with C2/m symmetry, and it melts to an isotropic liquid at 69 °C. The Colr phase of 4 is partially similar in its liquid crystalline structure to the neutral [Pt(Bdt)(C8,10bpy)] liquid crystal in a hexagonal columnar phase reported previously, while complex 4 shows a lower clearing point than that of the Pt analogue. Based on these results, the present study demonstrates the designability of the liquid crystalline structures of the [M(Bdt)(C8,10bpy)] skeleton together with their assembled structures and physico-chemical properties. [ABSTRACT FROM AUTHOR]

Four new bimetallic coordination polymers (CPs), {M[Pt(CN)2(5,5′-dcbpy)]·4H2O}n(M = Mg2+, Ca2+, Sr2+, Ba2+; 5,5′-H2dcbpy = 5,5′-dicarboxy-2,2′-bipyridine) were synthesized using four alkaline-earth metal ions and a Pt(ii)-diimine metalloligand [Pt(CN)2(5,5′-H2dcbpy)]. All four CPs are isomorphous with the Zn complex, {Zn[Pt(CN)2(5,5′-dcbpy)]·4H2O}n, which exhibits effective metallophilic interactions between Pt(ii) ions. These CPs exhibited colourful thermochromic behaviour and solid-state solvatochromic-like behaviours when suspended in various solvents. Thermogravimetric analysis and vapour-adsorption measurements revealed that the CPs can reversibly adsorb water and MeOH vapours. The emission energy of the triplet metal-metal-to-ligand charge-transfer (3MMLCT) state varied markedly upon guest adsorption/desorption. The chromic and vapour-adsorption properties of these CPs depend strongly on the cross-linking M2+ions. [ABSTRACT FROM AUTHOR]

We synthesized a thiosemicarbazone-functionalized flavin (Fl-(H)TSC: 2-[2-(3,4-dihydro-7,8-dimethyl-2,4-dioxobenzo[g]pteridin-10(2H)-yl)ethylidene]-hydrazinecarbothioamide) and its Pt(ii) complex [Pt(Fl-TSC)2], and characterized it using X-ray diffraction, UV–visible absorption and luminescence spectroscopy. X-ray structural analysis for [Pt(Fl-TSC)2] revealed that the structure of the isoalloxazine part was almost the same as that in lumiflavin (7,8,10-trimethylisoalloxazine), and the thiosemicarbazone moiety acted as a bidentate ligand to form a PtS2N2planar conformation. UV–visible absorption and luminescence spectra of these compounds were very similar to those of riboflavin, but the emission intensity and the lifetime decreased considerably. Theoretical calculations suggested that the charge-separated state (Fl−-TSC+) contributed to the faster quenching from the 1π–π* emission state. [ABSTRACT FROM AUTHOR]

A novel zeolite-like host framework was created by spontaneous aggregation of the title molecule in the solid state. X-Ray diffraction analysis showed that the geminal catechol-substituted molecules are linked together via a network of hydrogen bonds. The host framework is stabilized by small solvent molecules, trapped in the crystal cavities without any stronger than van der Waals' interaction between the guest and the surrounding host molecules. [ABSTRACT FROM AUTHOR]

Porous molecular crystals (PMCs) have gained significant importance as next-generation functional porous materials. However, the selective crystallisation of the PMC phase remains a challenge. Herein, we have systematically controlled the stability of the luminescent PMC phase prepared using the luminescent Pt(II) complex [Pt(pbim)(N^O)] (pbim = 2-phenylbenzimidazolate, N^O = N-heteroaryl carboxylate) with Pt⋯Pt electronic interactions. The PMC phase formation varied significantly among the complexes depending on the heteroaryl group of the ancillary N^O ligand; the oxazolyl-bearing complex did not form a PMC phase, whereas the pyrazyl- and 5-fluoropyridyl-bearing complexes spontaneously formed a porous structure. This difference was rationalised by the π-stacking capability of the heteroaryl group of the ancillary ligand. Furthermore, owing to the presence of the one-dimensional Pt⋯Pt chains in this PMC phase, the photophysical properties of PMCs resulting from the Pt⋯Pt interactions were also significantly changed by the ancillary ligands.

A coordination polymer, [Cu(SCN)(iqi)] n (iqi = isoquinoline), containing copper(I) thiocyanate and a nitrogen-containing π-conjugated ligand, iqi, has been synthesized and its physical properties were evaluated. This coordination polymer has a two-dimensional (2D) sheet structure consisting of copper(I) thiocyanate and shows photoluminescence derived from 3 MLCT and photoconductive properties.

Molecular crystals of Pt(II) complexes with metallophilic interactions can provide bright assembly-induced luminescence with colour tunability. However, the brittleness of many of these crystals makes their application in flexible optical materials difficult. Herein, we have achieved the elastic deformation of crystals of polyhalogenated Pt(II) complexes exhibiting bright assembly-induced luminescence. A crystal of [Pt(bpic)(dFppy)] (Hbpic = 5-bromopicolinic acid, HdFppy = 2-(2,4-difluorophenyl)pyridine) and a co-crystal of [Pt(bpic)(dFppy)] and [Pt(bpic)(ppy)] (Hppy = 2-phenylpyridine) were found to exhibit significant elastic deformation due to their highly anisotropic interaction topologies. While the crystal of [Pt(bpic)(dFppy)] exhibited monomer-based ligand-centred 3 ππ* emission with an emission quantum yield of 0.40, the co-crystal exhibited bright, triplet metal-metal-to-ligand charge transfer ( 3 MMLCT) emission owing to Pt⋯Pt interactions, thereby achieving a significantly higher emission quantum yield of 0.94.

We synthesized new oxygen-evolving molecular Ru(II) catalysts with one or two carbazole moieties on the axial pyridyl ligands, namely [Ru(bda)(cbz-py)(py)] and [Ru(bda)(cbz-py) 2 ] [C1 and C2; bdaH 2 = 2,2'-bipyridyl-6,6'-dicarboxylic acid, py = pyridine, and cbz-py = 9-(pyridin-4-yl)-9 H -carbazole] to investigate the effect of cbz modification on the photophysical and catalytic properties of the well-known molecular catalyst [Ru(bda)(py) 2 ] (C0). The initial oxygen-evolving catalytic activities of C1 and C2 were higher than that of C0 in both a chemical reaction driven by the strong oxidant (NH 4 ) 2 [Ce(NO 3 ) 6 ] (CAN = ceric ammonium nitrate) and photochemical oxidation using a [Ru(bpy) 3 ] 2+ (bpy = 2,2'-bipyridine) photosensitizer with Na 2 S 2 O 8 as the sacrificial oxidant. The higher activities were ascribed to the electron-withdrawing cbz groups, which promoted the radical coupling reaction to form a Ru IV -O-O-Ru IV species. A unique oxygen-evolution rate change behaviour was observed for both C1 and C2 in the presence of a large excess of CAN, suggesting the competitive oxidation of the cbz moiety during the chemical oxygen evolution reaction. This work suggests that the cbz modification of an oxygen evolution molecular catalyst is a promising approach for integrating the hole accumulator near the oxygen evolution catalytic centre.

A homogeneous thin film of a simple and highly luminescent Cu(i) complex, [CuI(PPh3)2(py)] (PPh3 = triphenylphosphine, py = pyridine) (Cu-py), was fabricated via spin coating using polyvinylpyrrolidone (PVP) and pyridine without destroying the complex. The thin film (Cu-py@PVP), with a thickness of 1 μm, exhibited efficient response to vapour, exhibiting reversible luminescence changes between blue-green and yellow upon exposure to vapours of N-heteroaromatic compounds such as py and 2-methylpyrazine (Mepyz). Vapochromic luminescence colour change resulting from ligand substitution was also observed in the crystal state, but the response of the thin film was remarkably faster than that of the crystalline samples. The vapour-induced ligand exchange on the thin film was fully characterised by comparing the luminescence properties of the Cu-py crystal with the newly prepared Cu(i) complex, [CuI(Mepyz)(PPh3)2] (Cu-Mepyz).

Controlled generation of homoleptic versus heteroleptic AuI2M (M = NiII, ZnII) trinuclear complexes, which is achieved by a slight change in the diphosphine P^P linker of digold(i) metalloligands, [Au2(P^P)(d-pen)2]2- (L1P^P; d-pen = d-penicillaminate) and [Au2(P^P)(l-cys)2]2- (L2P^P; l-cys = l-cysteinate), is reported. The reactions of a 1 : 1 mixture of L1dppm and L2dppm (dppm = bis(diphenylphosphino)methane) with M = NiII, ZnII gave the homoleptic AuI2M complexes, [M(L1dppm)] and [M(L2dppm)], which co-crystallized to form [M(L1dppm)]·[M(L2dppm)] (1M). Similar reactions using L1dppe and L2dppe (dppe = bis(diphenylphosphino)ethane), instead of L1dppm and L2dppm, led to the selective production and crystallization of the heteroleptic AuI2M complex, [M(L3dppe)] (2M; L3dppe = [Au2(dppe)(l-cys)(d-pen)]2-), accompanied by the scrambling of L1dppe and L2dppe. The homoleptic 1M and the heteroleptic 2M showed different absorption (green versus blue) and emission (yellow versus orange) colours for M = NiII and ZnII, respectively.

Luminescent ionic liquids, based on anionic Pt(ii) complexes, were developed. Depending on the cyclometalating ligands used, they exhibit thermochromic luminescence with different colours. The chromic properties in the flexible liquid and glass states emerge through the self-assembling character of the square-planar Pt(ii) complexes.

A luminescent Pt(ii) complex [Pt(CN) 2 (H 4 dpbpy)] (1P; H 4 dpbpy = 2,2'-bipyridine-4,4'-diphosphonic acid) bearing a phosphonic-acid-functionalized bipyridine ligand was successfully synthesized and its unique two-way vapochromic behaviour investigated. X-ray structure analyses of both the anhydrous 1P and penta-hydrated 1P·5H2O phases clearly reveal the activation of intermolecular PtPt interactions through the adsorption of water vapour. Emission spectroscopy reveals that the penta-hydrated 1P·5H2O complex exhibits an orange emission at 585 nm that shifts in two directions, to a blue-green emission at 469 nm by drying at 100 °C or to a red emission at 701 nm by drying under vacuum at room temperature. Thermogravimetric analyses and powder X-ray diffraction studies clearly reveal that anhydrous 1P, with negligible intermolecular PtPt interactions, is formed by drying at 100 °C whereas the monohydrate 1P·H2O phase, with effective PtPt interactions, is formed by drying under vacuum.

[CuCl(PPh 3 ) 2 (4-Mepy)] (PPh 3 = triphenylphosphine, 4-Mepy = 4-methylpyridine), a highly blue-luminescent mononuclear copper(i) complex, shows reversible emission colour change ranging from blue-green to red by vapour exposure to N-heteroaromatics, such as pyridine, pyrimidine, and 2-methylpyrazine. The remarkable colour changes occur due the ligand exchange reaction between the solid and gas. Such ligand exchange reactions would be applicable to various vapours with coordination ability and be useful for the sensing of such volatile organic compounds as well as a new convenient methodology for the preparation of luminescent complexes.

The stepwise reaction of a zwitterionic ligand, 4-methylamino-6-methyliminio-3-oxocyclohexa-1,4-dien-1-olate (QH2) with [Pt2(μ-Cl)2(ppy)2] (Hppy = 2-phenylpyridine) afforded a mononuclear complex, [Pt(ppy)(QH)] (1), and a dinuclear complex, [{Pt(ppy)}2(μ-Q)] (2). Using [Pd2(μ-Cl)2(ppy)2] in the second step resulted in the formation of a heterodinuclear complex, [{Pt(ppy)}(μ-Q){Pd(ppy)}] (3), which is the first heterodinuclear complex bridged by a quinonoid ligand. Single crystal X-ray diffraction analysis revealed that all three complexes adopted double-decker structures in the crystal. For 1, intermolecular N-HO interactions between uncoordinated N-H and O groups in two adjacent square-planar mononuclear units led to the formation of hydrogen-bonded dimers, which stacked to form a herringbone structure with a double-decker tetranuclear motif. For 2 and 3, dinuclear units bridged by Q(2-) formed a double-decker motif similar to that of 1, but a tetranuclear chain in the herringbone pattern was characteristic of the dinuclear complexes. PtPt (or PtPd) distances were more than 3.5 Å, twice the van der Waals radii of Pt, suggesting weak electronic metal-metal interactions in the crystal structures. Thus, the different colours observed (brown, purple, and dark green for 1, 2, and 3, respectively) mainly originated from the molecular structures. In fact, the three complexes exhibited colourful solutions of yellow, red, and green. UV-vis absorption spectroscopy and time-dependent density-functional theory (TD-DFT) calculations revealed that colour variations occurred depending on the electronic states composed of metal ions and the quinonoid ligand.

The redox-active metalloligand (RML) (Et3NH)3[Cr(III)(F4Cat)3] (F4Cat = perfluorocatecholato) () was synthesized and its interactions with guest metal ions Li(+), Mn(2+), Fe(2+), Co(2+), Cu(2+), and Zn(2+) were examined. Cyclic voltammetry measurements and spectroelectrochemical studies revealed that complex shows three-step ligand-centred one-electron oxidation to consecutively generate [Cr(III)(F4Cat)2(F4SQ)](2-) (F4SQ = perfluorosemiquinonato), [Cr(III)(F4Cat)(F4SQ)2](-), and [Cr(III)(F4SQ)3] at -0.12, 0.23, and 0.53 V vs. Ag/Ag(+) in dichloromethane, or at -0.21, 0.08, and 0.50 V in acetonitrile (MeCN), respectively. Titration experiments in MeCN revealed that treatment of with Cu(2+) leads to the formation of [Cr(III)(F4Cat)2(F4SQ)](2-) and Cu(+)via a redox reaction. However, when was treated with Li(+), Mn(2+), Fe(2+), Co(2+), and Zn(2+), further titration experiments revealed that these metal ions coordinated via the lone pairs on the coordinating oxygen atoms of the F4Cat(2-) moieties in a one-to-one ratio, and binding constants of 3.7 (±0.3) × 10(4) (Li(+)), 1.5 (±0.2) × 10(5) (Mn(2+)), 2.2 (±0.4) × 10(5) (Fe(2+)), 1.9 (±0.2) × 10(5) (Co(2+)), and 3.8 (±0.4) × 10(5) M(-1) (Zn(2+)) were established. Moreover, the oxidation potentials of were positively shifted by 0.08-0.33 V upon addition of guest metal ions. Spectroelectrochemical studies of in the presence of guest metal ions suggested that ligand-centred one- and two-electron oxidation of the RML occurred for Li(+), Mn(2+), Co(2+), and Zn(2+), respectively, while guest metal-centred one-electron oxidation was observed for Fe(2+). Considering all the aforementioned results, this study demonstrated for the first time the ability of [Cr(III)(F4Cat)3](3-) to act as a RML in solution.

A heterodinuclear complex, syn-[PtCu(μ-pyt)2(bpy)2](2+) (syn-[PtCu]; Hpyt = pyridine-2-thiol, bpy = 2,2'-bipyridine), was synthesized by stepwise complexation. Three different crystal structures of the hexafluorophosphate salts with solvent molecules as guests at the axial sites of the Cu(ii) ions, i.e. syn-[PtCu-G] (G = acetonitrile, acetone, and methanol), were determined by X-ray analyses. In the solid-state, these complexes adopt dimer-of-dimer motifs characteristic of the syn isomers of dinuclear complexes with two pyt bridging ligands arranged in a head-to-head configuration. These dinuclear complexes have a short PtCu distance (2.75-2.81 Å) and slightly different intermolecular PtPt distances (3.43-3.51 Å), which affect the colour of the solid complexes. All the syn-[PtCu-G] systems absorbed/desorbed vapour molecules; however, they exhibit different chromic changes because of the unique structural hysteresis of the desorbed form, i.e. syn-[PtCu], according to powder X-ray diffraction measurements. In addition, guest exchange occurred in the syn-[PtM-G] complexes upon exposure to the vapour of different solvents.

The introduction of a Au(III) ion into a mesogenic core, [M(Bdt)(Cnbpy)](+) (Bdt = 1,2-benzenedithiolato and Cnbpy = 4,4'-di-alkyl-2,2'-bipyridine (n = 13 (4,4'-di-tridecyl-2,2'-bipyridine (C13bpy)) and 8,10 (4,4'-di-(3-octyltridecyl)-2,2'-bipyridine (C8,10bpy)))), leads to the formation of ionic molecular assemblies in crystalline and mesophases. Successive syntheses of precursor complexes, [AuCl2(Cnbpy)]PF6 (n = 13 (1) and 8,10 (2)), followed by the target complexes, [Au(Bdt)(Cnbpy)]PF6 (n = 13 (3) and 8,10 (4)), were achieved. The crystallographic analysis of 3 revealed that the central cationic cores form a characteristic one-dimensional columnar structure, which is an essential property for the formation of columnar structures in the liquid crystalline phase. The central cores of the [Au(Bdt)(C13bpy)](+) cations in 3 stack alternatively so as to cancel out their dipole moments and the counteranions lie between the cationic columns. Furthermore, the introduction of the branched alkyl tails in 4 induces the formation of a rectangular columnar liquid crystalline phase (Col(r)) with C2/m symmetry, and it melts to an isotropic liquid at 69 °C. The Col(r) phase of 4 is partially similar in its liquid crystalline structure to the neutral [Pt(Bdt)(C8,10bpy)] liquid crystal in a hexagonal columnar phase reported previously, while complex 4 shows a lower clearing point than that of the Pt analogue. Based on these results, the present study demonstrates the designability of the liquid crystalline structures of the [M(Bdt)(C8,10bpy)] skeleton together with their assembled structures and physico-chemical properties.

Heterodinuclear complexes, syn-[MPt(μ-pyt)2(bpy)2](n+) (syn-[MPt], M = Pd(2+), Au(3+), Hpyt = pyridine-2-thiol, bpy = 2,2'-bipyridine), were synthesized as a selective geometrical isomer by stepwise complexation. X-ray analyses of the hexafluorophosphate salts of these complexes proved their dinuclear structures with short M···Pt distances (2.9084(4) Å for syn-[PdPt] and 2.9071(4) Å for syn-[AuPt]), similar to the homodinuclear complex (2.9292(2) Å for syn-[PtPt]). In the syn-[PdPt] crystal, two dinuclear motifs are arranged closely in a head-to-head manner with a short Pt···Pt distance (3.3757(3) Å), forming a dimer-of-dimer structure as in the case of syn-[PtPt], whereas the corresponding crystal of syn-[AuPt] has a discrete arrangement of the dinuclear motifs. By the isomerisation of syn-[PdPt], anti-[PdPt] with equivalent environments of the Pd(2+) and Pt(2+) ions was also obtained successfully. Syn-[PdPt](PF6)2 exhibits vapochromic behaviour based on the absorption/desorption of CH3CN vapour, similar to that observed for syn-[PtPt](PF6)2. The reversible structural transformations induced by the uptake and release of CH3CN molecules were investigated by powder and single-crystal X-ray diffraction studies. These revealed that the vapochromic behaviour was based on the interconversion between two phases, the dimer-of-dimer structure with a short Pt···Pt distance and a π-π stacked arrangement with no Pt···Pt intermolecular interaction. The introduction of the heterometal ions enabled control of the colour region: orange ↔ red for syn-[PdPt] vs. light red ↔ dark red for syn-[PtPt], reflecting the weaker metal-metal interaction between Pd(2+) and Pt(2+) ions in the dinuclear motif. In addition, these complexes were found to exhibit mechanochromic behaviour based on a crystal-to-amorphous transformation upon grinding, and the reconstruction of the crystal structures by vapour sorption.

Dinuclear complexes [{Pt(trpy)}(2)(L)](PF(6))(2) (trpy = 2,2':6',2''-terpyridine, L = 2-octylthio-1,3,5-triazine-4,6-dithiolate ion (1), L = 2-octadecylthio-1,3,5-triazine-4,6-dithiolate ion (2), L = 2-di-n-butylamino-1,3,5-triazine-4,6-dithiolate ion (3)) and a trinuclear complex [{Pt(trpy)}(3)(L)](PF(6))(3) (L = 1,3,5-triazine-2,4,6-trithiolate ion (4)) have been synthesized and characterized. The single crystal X-ray analysis revealed that the two {Pt(trpy)}(2+) fragments in 1 and 3 adopt a syn-configuration. The PtPt distances are around 4.3 Å, suggesting no intramolecular PtPt interactions. Complexes 1-4 in acetonitrile show broad absorption bands at around 470 nm, assigned to mainly the ligand-to-ligand charge transfer ((1)LLCT) from triazine thiolates to trpy based on the comparison to the related complexes and the density functional theory (DFT) calculations. The red luminescence of 1-4 in acetonitrile is attributable to emission predominantly from (3)LLCT. Cyclic voltammograms of 1-3 exhibit four redox couples from -2.0 V to 0 V vs. Ag/AgCl. The two consecutive processes at around -0.70 V are assigned to the sequential reduction of two trpy ligands. This assignment was further supported by the observation of the anion radical of trpy in spectroelectrochemical experiments. The splitting of the redox potentials of two trpy ligands evidences the moderate electronic coupling interactions mediated by the triazine dithiolate bridges. Complex 2 formed a transparent red gel in CH(3)CN, whereas 4 produced a gel-like solid in the mixtures of CH(3)CN and other solvents. The interactions dominating the aggregative behaviours have been discussed based on the results of electronic absorption and emission spectroscopy.