Vapor-Controlled Linkage Isomerization of a Vapochromic Bis(thiocyanato)platinum(II) Complex: New External Stimuli To Control Isomerization Behavior

We synthesized a novel Pt­(II)–diimine complex with a typical ambidentate thiocyanato ligand, [Pt­(<i>thiocyanato</i>)₂(H₂dcbpy)] (<b>1</b>; H₂dcbpy =4,4′-dicarboxy-2,2′-bipyridine), and found that the complex <b>1</b> exhibits unique linkage isomerizations with drastic color and luminescence changes driven by exposure to volatile organic chemical (VOC) vapors in the solid state. Reaction between [PtCl₂(H₂dcbpy)] and KSCN in aqueous solution at 0 °C enabled successful isolation of an isomer with the S-coordinated thiocyanato ligand, [Pt­(<u>S</u>CN)₂(H₂dcbpy)] (<b>1SS·H</b>_<b>2</b><b>O</b>), as a nonluminescent orange solid. Interestingly, <b>1SS·H</b>_<b>2</b><b>O</b> was isomerized completely to one isomer with the N-coordinated isothiocyanato ligand, [Pt­(<u>N</u>CS)₂(H₂dcbpy)] (<b>1NN·3DMF</b>) by exposure to DMF vapor, and this isomerization was accompanied by significant color and luminescence changes from nonluminescent orange to luminescent red. IR spectroscopy and thermogravimetric analysis revealed that adsorption of the DMF vapor and transformation of the hydrogen-bonded structure both played important roles in this vapor-induced linkage isomerization. Another isomer containing both S- and N-coordinated thiocyanato ligands, [Pt­(<u>S</u>CN)­(<u>N</u>CS)­(H₂dcbpy)] (<b>1SN</b>), was obtained as a nonluminescent yellow solid simply by exposure of <b>1SS·H</b>_<b>2</b><b>O</b> to acetone vapor at room temperature, and about 80% of <b>1SS·H</b>_<b>2</b><b>O</b> was found to be converted to <b>1SN</b>. In the solution state, each isomer changed gradually to an isomeric mixture, but pure <b>1SS</b> was regenerated by UV light irradiation (λ_irr. = 300 nm) of an MeOH solution of the mixture. In the crystal structure of <b>1SN</b>, the complex molecules were hydrogen-bonded to each other through the carboxyl groups of the H₂dcbpy ligand and the N site of the thiocyanato ligand, whereas the <b>1NN</b> molecules in the <b>1NN·4DMF</b> crystal were hydrogen-bonded to the solvated DMF molecules. Competition of the hydrogen-bonding ability among the carboxyl groups of the H₂dcbpy ligand, N and S atoms of the thiocyanato ligand, and the vapor molecule was found to be one of the most important factors controlling linkage isomerization behavior in the solid state. This unique linkage isomerization controlled by vapor can provide an outstanding vapochromic system as well as a new molecular switching function driven by vapor molecules

Vapor-Controlled Linkage Isomerization of a Vapochromic Bis(thiocyanato)platinum(II) Complex: New External Stimuli To Control Isomerization Behavior

We synthesized a novel Pt­(II)–diimine complex with a typical ambidentate thiocyanato ligand, [Pt­(<i>thiocyanato</i>)₂(H₂dcbpy)] (<b>1</b>; H₂dcbpy =4,4′-dicarboxy-2,2′-bipyridine), and found that the complex <b>1</b> exhibits unique linkage isomerizations with drastic color and luminescence changes driven by exposure to volatile organic chemical (VOC) vapors in the solid state. Reaction between [PtCl₂(H₂dcbpy)] and KSCN in aqueous solution at 0 °C enabled successful isolation of an isomer with the S-coordinated thiocyanato ligand, [Pt­(<u>S</u>CN)₂(H₂dcbpy)] (<b>1SS·H</b>_<b>2</b><b>O</b>), as a nonluminescent orange solid. Interestingly, <b>1SS·H</b>_<b>2</b><b>O</b> was isomerized completely to one isomer with the N-coordinated isothiocyanato ligand, [Pt­(<u>N</u>CS)₂(H₂dcbpy)] (<b>1NN·3DMF</b>) by exposure to DMF vapor, and this isomerization was accompanied by significant color and luminescence changes from nonluminescent orange to luminescent red. IR spectroscopy and thermogravimetric analysis revealed that adsorption of the DMF vapor and transformation of the hydrogen-bonded structure both played important roles in this vapor-induced linkage isomerization. Another isomer containing both S- and N-coordinated thiocyanato ligands, [Pt­(<u>S</u>CN)­(<u>N</u>CS)­(H₂dcbpy)] (<b>1SN</b>), was obtained as a nonluminescent yellow solid simply by exposure of <b>1SS·H</b>_<b>2</b><b>O</b> to acetone vapor at room temperature, and about 80% of <b>1SS·H</b>_<b>2</b><b>O</b> was found to be converted to <b>1SN</b>. In the solution state, each isomer changed gradually to an isomeric mixture, but pure <b>1SS</b> was regenerated by UV light irradiation (λ_irr. = 300 nm) of an MeOH solution of the mixture. In the crystal structure of <b>1SN</b>, the complex molecules were hydrogen-bonded to each other through the carboxyl groups of the H₂dcbpy ligand and the N site of the thiocyanato ligand, whereas the <b>1NN</b> molecules in the <b>1NN·4DMF</b> crystal were hydrogen-bonded to the solvated DMF molecules. Competition of the hydrogen-bonding ability among the carboxyl groups of the H₂dcbpy ligand, N and S atoms of the thiocyanato ligand, and the vapor molecule was found to be one of the most important factors controlling linkage isomerization behavior in the solid state. This unique linkage isomerization controlled by vapor can provide an outstanding vapochromic system as well as a new molecular switching function driven by vapor molecules

Integration of Alkyl-Substituted Bipyridyl Benzenedithiolato Platinum(II) Complexes with Cadmium(II) Ion via Selective Dative Bond Formation

The presence of lone pairs on the Pt and S atoms of [Pt­(Bdt)­(DTBbpy)] (<b>1</b>) (Bdt = 1,2-benzenedithiolato and DTBbpy = 4,4′-di-<i>tert</i>-butyl-2,2′-bipyridine) and [Pt­(Bdt)­(C13bpy)] (<b>2</b>) (C13bpy = 4,4′-ditridecyl-2,2′-bipyridine) led to selective dative bond formation with Cd­(II). Complexes <b>1</b> and <b>2</b> show no binding interaction with Zn­(II), while they bind selectively with Cd­(II) to give a twisted trinuclear complex, [Cd­{Pt­(Bdt)­(DTBbpy)}₂(ClO₄)­(H₂O)]­(ClO₄) (<b>3</b>), and a shuttlecock-shaped tetranuclear complex, [Cd­{Pt­(Bdt)­(C13bpy)}₃(H₂O)]­(ClO₄)₂·CH₂Cl₂ (<b>4</b>), respectively, depending upon the alkyl groups substituted on the 2,2′-bipyridine. The two platinum moieties in <b>3</b> are connected to the seven-coordinated Cd atom through Pt → Cd (2.7331(7) and 2.7936(7) Å) and S → Cd (2.690(3), 2.940(3), and 3.067(3) Å) dative bonds, while the three moieties in <b>4</b> are connected to the tetrahedral Cd atom only by S → Cd (2.552(4) Å) dative bonds. These structural variations found in <b>3</b> and <b>4</b> are caused not only by steric hindrance of the <i>t</i>-Bu groups but also by the microsegregation effect derived from the tridecyl chains. The three platinum moieties in <b>4</b> align so as to form a parallel orientation of their dipole moments, in contrast to the twisted arrangement found in <b>3</b>. The dative bonds formed in <b>3</b> and <b>4</b> are commonly stable in the solid state and in less coordinative solvents such as dichloromethane, while dissociation behavior of platinum moieties with Cd­(II) was observed in more coordinative THF. UV–vis and NMR spectroscopy unsealed the characteristic association/dissociation properties depending on the coordination abilities of solvents. Finally, the present study revealed that the formation of dative bonds between the platinum moieties with Cd­(II) plays important roles not only in stabilizing the ground states, which leads to blue shifts in both absorption and emission energies, but also in electronic interactions between the moieties, which are revealed by electrochemical studies

Vapochromic Luminescence and Flexibility Control of Porous Coordination Polymers by Substitution of Luminescent Multinuclear Cu(I) Cluster Nodes

Two luminescent porous coordination polymers (PCPs), i.e., [Cu₂(μ₂-I)₂ctpyz]_<i>n</i> and [Cu₄(μ₃-I)₄ctpyz]_<i>n</i> (<b>Cu2</b> and <b>Cu4</b>, respectively; ctpyz = <i>cis</i>-1,3,5-cyclohexanetriyl-2,2′,2″-tripyrazine), were successfully synthesized and characterized by single-crystal X-ray diffraction and luminescence spectroscopic measurements. <b>Cu2</b> consists of rhombus-type dinuclear {Cu₂I₂} cores bridged by ctpyz ligands, while <b>Cu4</b> is constructed of cubane-type tetranuclear {Cu₄I₄} cores bridged by ctpyz ligands. The void fraction of <b>Cu4</b> is estimated to be 48.0%, which is significantly larger than that of <b>Cu2</b> (19.9%). Under UV irradiation, both PCPs exhibit red luminescence at room temperature in the solid state (λ_em values of 660 and 614 nm for <b>Cu2</b> and <b>Cu4</b>, respectively). Although the phosphorescence of <b>Cu2</b> does not change upon removal and/or adsorption of EtOH solvent molecules in the porous channels, the solid-state emission maximum of <b>Cu4</b> red-shifts by 36 nm (λ_em = 650 nm) upon the removal of the adsorbed benzonitrile (PhCN) molecules from the porous channels (and vice versa). This large difference in the vapochromic behavior of <b>Cu2</b> and <b>Cu4</b> is closely related to the framework flexibility. The framework of <b>Cu2</b> is sufficiently rigid to retain the porous structure without solvated EtOH molecules, whereas the porous structure of <b>Cu4</b> collapses easily after removal of the adsorbed PhCN molecules to form a nonporous amorphous phase. The original vapor-adsorbed porous structure of <b>Cu4</b> is regenerated by exposure of the amorphous solid to not only PhCN vapor but also tetrahydrofuran, acetone, ethyl acetate, and <i>N</i>,<i>N</i>-dimethylformamide vapors. The <b>Cu4</b> structures with the various adsorbed solvents showed almost the same emission maxima as the original PhCN-adsorbed <b>Cu4</b>, except for DMF-adsorbed <b>Cu4</b>, which showed no luminescence probably because of weak coordination of the DMF vapor molecules to the Cu­(I) centers of the tetranuclear {Cu₄I₄} core

Flexible Coordination Polymers Composed of Luminescent Ruthenium(II) Metalloligands: Importance of the Position of the Coordination Site in Metalloligands

Coordination polymerization reactions between ruthenium­(II) metalloligands [Ru­(<i>n</i>,<i>n</i>′-dcbpy)]^4– (<b>[</b><i><b>n</b></i><b>Ru]</b>; <i>n</i> = 4, 5; <i>n</i>,<i>n</i>′-dcbpy = <i>n</i>,<i>n</i>′-dicarboxy-2,2′-bipyridine) and several divalent metal salts in basic aqueous solutions afforded porous luminescent complexes formulated as [Mg­(H₂O)₆]­{[Mg­(H₂O)₃]­[4Ru]·4H₂O} (<b>Mg</b>_<b>2</b><b>[4Ru]·13H</b>_<b>2</b><b>O</b>), [Mg₂(H₂O)₉]­[5Ru]·10H₂O (<b>Mg</b>_<b>2</b><b>[5Ru]·19H</b>_<b>2</b><b>O</b>), {[Sr₄(H₂O)₉]­[4Ru]₂·9H₂O} (<b>Sr</b>_<b>2</b><b>[4Ru]·9H</b>_<b>2</b><b>O</b>)₂, {[Sr₂(H₂O)₈]­[5Ru]·6H₂O} (<b>Sr</b>_<b>2</b><b>[5Ru]·14H</b>_<b>2</b><b>O</b>), and {[Cd₂(H₂O)₂]­[5Ru]·10H₂O} (<b>Cd</b>_<b>2</b><b>[5Ru]·12H</b>_<b>2</b><b>O</b>). Single-crystal X-ray structural analyses revealed that the divalent metal ions were commonly coordinated by the carboxyl groups of the <b>[</b><i><b>n</b></i><b>Ru]</b> metalloligand, forming porous frameworks with a void fraction varying from 11.4% <b>Mg</b>_<b>2</b><b>[4Ru]·13H</b>_<b>2</b><b>O</b> to 43.9% <b>Cd</b>_<b>2</b><b>[5Ru]·12H</b>_<b>2</b><b>O</b>. <b>M</b>_<b>2</b><b>[4Ru]·</b><i><b>n</b></i><b>H</b>_<b>2</b><b>O</b> showed a reversible structural transition accompanied by water and methanol vapor adsorption/desorption, while the porous structures of <b>M</b>_<b>2</b><b>[5Ru]·</b><i><b>n</b></i><b>H</b>_<b>2</b><b>O</b> were irreversibly collapsed by the removal of crystal water. The triplet metal-to-ligand charge-transfer emission energies of <b>M</b>_<b>2</b><b>[4Ru]·</b><i><b>n</b></i><b>H</b>_<b>2</b><b>O</b> were lower than those of <b>[4Ru]</b> in aqueous solution, whereas those of <b>M</b>_<b>2</b><b>[5Ru]·</b><i><b>n</b></i><b>H</b>_<b>2</b><b>O</b> were close to those of <b>[5Ru]</b> in aqueous solution. These results suggested that the position of the coordination site in the metalloligand played an important role not only on the structure of the porous framework but also on the structural flexibility involving the guest adsorption/desorption properties

Photo- and Vapor-Controlled Luminescence of Rhombic Dicopper(I) Complexes Containing Dimethyl Sulfoxide

Halide-bridged rhombic dicopper­(I) complexes, [Cu₂­(μ-X)₂­(DMSO)₂­(PPh₃)₂] (X = I^–, Br^–; DMSO = dimethyl sulfoxide; PPh₃ = triphenylphosphine), were synthesized, the iodide complex of which exhibited interesting photochromic luminescence driven by photoirradiation and by exposure to DMSO vapor in the solid state. Single-crystal X-ray diffraction measurements revealed that the iodo and bromo complexes (abbreviated <b>Cu</b>_<b>2</b><b>I</b>_<b>2</b><b>-[O,O]</b> and <b>Cu</b>_<b>2</b><b>Br</b>_<b>2</b><b>-[O,O]</b>) were isomorphous, and that the two DMSO ligands were coordinated to the Cu­(I) ion via the O atom in both complexes. Both complexes exhibited bright blue phosphorescence at room temperature (λ_em = 435 nm, Φ_em = 0.19 and 0.14 for <b>Cu</b>_<b>2</b><b>I</b>_<b>2</b><b>-[O,O]</b> and <b>Cu</b>_<b>2</b><b>Br</b>_<b>2</b><b>-[O,O]</b>, respectively) with a relatively long emission lifetime (τ_em ∼ 200 μs at 77 K) derived from the mixed halide-to-ligand and metal-to-ligand charge transfer (³XLCT and ³MLCT) excited state. Under UV irradiation, the blue phosphorescence of <b>Cu</b>_<b>2</b><b>Br</b>_<b>2</b><b>-[O,O]</b> disappeared uneventfully and no new emission band appeared, whereas the blue phosphorescence of <b>Cu</b>_<b>2</b><b>I</b>_<b>2</b><b>-[O,O]</b> rapidly disappeared with simultaneous appearance of a new green emission band (λ_em = 500 nm). On further irradiation, the green emission of the iodide complex gradually changed to bright yellowish-green (λ_em = 540 nm); however, this change could be completely suppressed by lowering the temperature to 263 K or in the presence of saturated DMSO vapor. The initial blue phosphorescence of <b>Cu</b>_<b>2</b><b>I</b>_<b>2</b><b>-[O,O]</b> was recovered by exposure to DMSO vapor at 90 °C for a few hours. IR spectroscopy and theoretical calculations suggest that the DMSO ligand underwent linkage isomerization from O-coordination to S-coordination, and both the occurrence of linkage isomerization and the removal of DMSO result in contraction of the rhombic Cu₂­(μ-I)₂ core to make the Cu···Cu interaction more effective. In the contracted core, the triplet cluster-centered (³CC) emissive state is easily generated by thermal excitation of the ³XLCT and ³MLCT mixed transition state, resulting in the green to yellowish-green emission. In contrast, the Cu···Cu distance in <b>Cu</b>_<b>2</b><b>Br</b>_<b>2</b><b>-[O,O]</b> is considerably longer than that of <b>Cu</b>_<b>2</b><b>I</b>_<b>2</b><b>-[O,O]</b>, which destabilizes the ³CC emissive state, resulting in the nonemissive character

Photoinduced Dimerization Reaction Coupled with Oxygenation of a Platinum(II)–Hydrazone Complex

Photoreactivities of Ni­(II)– and Pt­(II)–hydrazone complexes, [NiCl­(L)] (<b>Ni1</b>) and [PtCl­(L)] (<b>Pt1</b>), respectively [<b>HL</b> = 2-(diphenylphosphino)­benzaldehyde-2-pyridylhydrazone], were investigated in detail via UV–vis absorption, ¹H nuclear magnetic resonance (NMR) spectroscopy, and electrospray ionization time-of-flight (ESI-TOF) mass spectrometry; the two photoproducts obtained from the photoreaction of <b>Pt1</b> were also successfully identified via X-ray analysis. The absorption bands of the <b>Ni1</b> and <b>Pt1</b> complexes were very similar, centered around 530 nm, and were assigned as an intraligand charge transfer transition of the hydrazone moiety. The absorption spectrum of <b>Pt1</b> in a CH₃CN solution changed drastically upon photoirradiation (λ = 530 nm), whereas no change was observed for <b>Ni1</b>. ¹H NMR and ESI-TOF mass spectra under various conditions suggested that the photoexcited <b>Pt1*</b> reacts with dissolved dioxygen to form a reactive intermediate, and the ensuing dark reactions afforded two different products without any decomposition. In contrast to the simple photo-oxidation of <b>HL</b> to form a phosphine oxide <b>HL­(P</b><b>O)</b>, the X-ray crystallographic analyses of the photoproducts clearly indicate the formation of a mononuclear Pt complex with the oxygenated hydrazone ligand (<b>Pt1O</b>) and a dinuclear Pt complex with the oxygenated and dimerized hydrazone ligand (<b>Pt2</b>). The photosensitized reaction in the presence of an ¹O₂-generating photosensitizer, methylene blue (MB), also produced <b>Pt1O</b> and <b>Pt2</b>, indicating that the reaction between ¹O₂ and ground-state <b>Pt1</b> is the important step. In a highly viscous dimethyl sulfoxide solution, <b>Pt1</b> was slowly, but quantitatively, converted to the mononuclear form, <b>Pt1O</b>, without the formation of the dinuclear product, <b>Pt2</b>, upon photoirradiation (and in the reaction photosensitized by MB), suggesting that this photoreaction of <b>Pt1</b> involves at least one diffusion-controlled reaction. On the other hand, the same complexes <b>Pt1O</b> and <b>Pt2</b> were also produced in the degassed solution, probably because of the reaction of the photoexcited <b>Pt1*</b> with the biradical character and H₂O

Photo- and Vapor-Controlled Luminescence of Rhombic Dicopper(I) Complexes Containing Dimethyl Sulfoxide

Halide-bridged rhombic dicopper­(I) complexes, [Cu₂­(μ-X)₂­(DMSO)₂­(PPh₃)₂] (X = I^–, Br^–; DMSO = dimethyl sulfoxide; PPh₃ = triphenylphosphine), were synthesized, the iodide complex of which exhibited interesting photochromic luminescence driven by photoirradiation and by exposure to DMSO vapor in the solid state. Single-crystal X-ray diffraction measurements revealed that the iodo and bromo complexes (abbreviated <b>Cu</b>_<b>2</b><b>I</b>_<b>2</b><b>-[O,O]</b> and <b>Cu</b>_<b>2</b><b>Br</b>_<b>2</b><b>-[O,O]</b>) were isomorphous, and that the two DMSO ligands were coordinated to the Cu­(I) ion via the O atom in both complexes. Both complexes exhibited bright blue phosphorescence at room temperature (λ_em = 435 nm, Φ_em = 0.19 and 0.14 for <b>Cu</b>_<b>2</b><b>I</b>_<b>2</b><b>-[O,O]</b> and <b>Cu</b>_<b>2</b><b>Br</b>_<b>2</b><b>-[O,O]</b>, respectively) with a relatively long emission lifetime (τ_em ∼ 200 μs at 77 K) derived from the mixed halide-to-ligand and metal-to-ligand charge transfer (³XLCT and ³MLCT) excited state. Under UV irradiation, the blue phosphorescence of <b>Cu</b>_<b>2</b><b>Br</b>_<b>2</b><b>-[O,O]</b> disappeared uneventfully and no new emission band appeared, whereas the blue phosphorescence of <b>Cu</b>_<b>2</b><b>I</b>_<b>2</b><b>-[O,O]</b> rapidly disappeared with simultaneous appearance of a new green emission band (λ_em = 500 nm). On further irradiation, the green emission of the iodide complex gradually changed to bright yellowish-green (λ_em = 540 nm); however, this change could be completely suppressed by lowering the temperature to 263 K or in the presence of saturated DMSO vapor. The initial blue phosphorescence of <b>Cu</b>_<b>2</b><b>I</b>_<b>2</b><b>-[O,O]</b> was recovered by exposure to DMSO vapor at 90 °C for a few hours. IR spectroscopy and theoretical calculations suggest that the DMSO ligand underwent linkage isomerization from O-coordination to S-coordination, and both the occurrence of linkage isomerization and the removal of DMSO result in contraction of the rhombic Cu₂­(μ-I)₂ core to make the Cu···Cu interaction more effective. In the contracted core, the triplet cluster-centered (³CC) emissive state is easily generated by thermal excitation of the ³XLCT and ³MLCT mixed transition state, resulting in the green to yellowish-green emission. In contrast, the Cu···Cu distance in <b>Cu</b>_<b>2</b><b>Br</b>_<b>2</b><b>-[O,O]</b> is considerably longer than that of <b>Cu</b>_<b>2</b><b>I</b>_<b>2</b><b>-[O,O]</b>, which destabilizes the ³CC emissive state, resulting in the nonemissive character

Systematic Syntheses and Metalloligand Doping of Flexible Porous Coordination Polymers Composed of a Co(III)–Metalloligand

A series of flexible porous coordination polymers (PCPs) <b>RE–Co</b>, composed of a Co­(III)–metalloligand [Co­(dcbpy)₃]^3– (<b>Co</b>; H₂dcbpy = 4,4′-dicarboxy-2,2′-bipyridine) and lanthanide cations (RE³⁺ = La³⁺, Ce³⁺, Pr³⁺, Nd³⁺, Sm³⁺, Eu³⁺, Gd³⁺, Tb³⁺, Er³⁺), was systematically synthesized. X-ray crystallographic analysis revealed that the six carboxylates at the top of each coordination octahedron of Co­(III)–metalloligand were commonly bound to RE³⁺ cations to form a rock-salt-type porous coordination framework. When <b>RE–Co</b> contains a smaller and heavier RE³⁺ cation than Nd³⁺, the <b>RE–Co</b> crystallized in the cubic <i><i>Fm</i>-3<i>m</i></i> space group, whereas the other three <b>RE–Co</b> with larger RE³⁺ crystallized in the lower symmetrical orthorhombic <i>Fddd</i> space group, owing to the asymmetric 10-coordinated bicapped square antiprism structure of the larger RE³⁺ cation. Powder X-ray diffraction and vapor-adsorption isotherm measurements revealed that all synthesized <b>RE–Co</b> PCPs show reversible amorphous–crystalline transitions, triggered by water-vapor-adsorption/desorption. This transition behavior strongly depends on the kind of RE³⁺; the transition of orthorhombic <b>RE–Co</b> was hardly observed under exposure to CH₃OH vapor, but the <b>RE–Co</b> with smaller cations such as Gd³⁺ showed the transition under exposure to CH₃OH vapors. Further tuning of vapor-adsorption property was examined by doping of Ru­(II)–metalloligands, [Ru­(dcbpy)₃]^4–, [Ru­(dcbpy)₂Cl₂]^4–, [Ru­(dcbpy)­(tpy)­Cl]⁻, and [Ru­(dcbpy)­(dctpy)]^3– (abbreviated as <i><b>Ru</b></i><b>A</b>, <i><b>Ru</b></i><b>B</b>, <i><b>Ru</b></i><b>C</b>, and <i><b>Ru</b></i><b>D</b>, respectively; tpy = 2,2′:6′,2″-terpyridine, H₂dctpy = 4,4″-dicarboxy-2,2′:6′,2″-terpyridine), into the Co­(III)–metalloligand site of <b>Gd–Co</b> to form the Ru­(II)-doped PCP <i><b>Ru</b></i><b>X@Gd–Co</b> (X = A, B, C, or D). Three Ru­(II)–metalloligands, <i><b>Ru</b></i><b>A</b>, <i><b>Ru</b></i><b>B</b>, and <i><b>Ru</b></i><b>D</b> dopants, were found to be uniformly incorporated into the <b>Gd–Co</b> framework by replacing the original Co­(III)–metalloligand, whereas the doping of <i><b>Ru</b></i><b>C</b> failed probably because of the less number of coordination sites. In addition, we found that the <i><b>Ru</b></i><b>A</b> doping into the <b>Gd–Co</b> PCP had a large effect on vapor-adsorption due to the electrostatic interaction originating from the negatively charged <i><b>Ru</b></i><b>A</b> sites in the framework and the charge-compensating Li⁺ cations in the porous channel

Nonprecious-Metal-Assisted Photochemical Hydrogen Production from <i>ortho</i>-Phenylenediamine

The combination of <i>o</i>-phenylenediamine (opda), which possesses two proton- and electron-pooling capability, with Fe­(II) leads to the photochemical hydrogen-evolution reaction (HER) in THF at room temperature without addition of photosensitizers. From the THF solution, the tris­(<i>o</i>-phenylenediamine) iron­(II) complex, [Fe^II(opda)₃]­(ClO₄)₂ (<b>1</b>), was isolated as a photoactive species, while the deprotonated oxidized species was characterized by X-ray crystallographic analysis, electrospray ionization mass spectrometry, and UV–vis NIR spectra. Furthermore, the HER is photocatalyzed by hydroquinone, which serves as a H⁺/e^– donor. The present work demonstrates that the use of a metal-bound aromatic amine as a H⁺/e^– pooler opens an alternative strategy for designing nonprecious-metal-based molecular photochemical H₂ production/storage materials