One-dimensional supramolecular assemblies based on a Re2(III,III) synthon and their solid-state phosphorescence

Reactions between Re2(DMBA)4(NO3)2 (1; DMBA is dimethylbenzamidinate) and a bidentate dianion, either tungstate (WO4(2-)) or terephthalte (1,4-(O2C)2C6H4(2-)), resulted in the one-dimensional coordination polymers [Re2(DMBA)4(mu-O,O'-WO4)](infinity) (2) and [Re2(DMBA)4(mu-O,O'-1,4-(O2C)2C6H4)](infinity) (3), respectively. Both polymers display phosphorescence from a 3(delta --> delta*) state, which is significantly blue shifted from the phosphorescence previously observed for Re2(DMBA)4Cl2 type compounds.     

The Synthesis and Characterization of Re2(Xap)4Cl2 Compounds

Five dirhenium(III) compounds, Re₂(3,5-(CH₃)₂ap)₄Cl₂ (1), Re₂(ap)₄Cl₂ (2), Re₂(3-MeOap)₄Cl₂ (3), Re₂(3-Clap)₄Cl₂ (4), and Re₂(3,5-Cl₂ap)₄Cl₂ (5), were synthesized and characterized, where 3,5-(CH₃)₂ap, ap, 3-MeOap, 3-Clap and 3,5-Cl₂ap are 2-(3,5-dimethylanilino)pyridinate, 2-anilinopyridinate, 2-(3-methoxyanilino)pyridinate, 2-(3-chloroanilino)pyridinate and 2-(3,5-dichloroanilino)pyridinate, respectively. Structural studies revealed the Re–Re bond lengths ranging from 2.2214(4) to 2.2262(11) Å, signifying that the dirhenium core maintains its quadruple bond. The asymmetric nature of 2-anilinopyridinate ligands resulted in several possible regioisomers: compounds 1 and 4 adopt a cis-(2,2) arrangement, while compounds 2 and 5 assume trans-(2,2) and (3,1) arrangements, respectively. All five compounds display three (quasi)reversible one electron couples, two oxidations and one reduction, and their electrode potentials correlate linearly with the Hammett constant of the aniline substituent.     

Dirhenium paddlewheel compounds supported by N,N'-dialkylbenzamidinates: synthesis, structures, and photophysical properties

Dirhenium(III,III) compounds Re2(DMBA)4Cl2 (1, DMBA=N,N'-dimethylbenzamidinate) and Re2(DEBA)4Cl2 (2, DEBA=N,N'-diethylbenzamidinate) were synthesized via molten reactions between Re2(OAc)4Cl2 and the corresponding amidine. Re2(DMBA)4(NO3)2 (3) was obtained through reacting Re2(DMBA)4Cl2 with AgNO3. Single crystal X-ray diffraction studies revealed that the Re-Re distances in compounds 1-3 are 2.212(1), 2.217(1), and 2.173(1) A, respectively, which are consistent with the presence of a Re-Re quadruple bond. Voltammetric studies revealed that compound 2 exhibits two quasireversible couples, an oxidation and a reduction, and an irreversible reduction, while compound 1 displays irreversible couples at similar potentials. The three complexes exhibit 1deltadelta* absorption as a shoulder at approximately 440 nm (epsilon approximately 1500 M(-1) cm(-1)). Upon excitation of solid samples or CH2Cl2 solutions of 2 with visible light, emission is observed at 824 nm (77 K) and 833 nm (298 K), respectively. The luminescence is assigned as arising from the 3deltadelta* excited state.     

Dirhenium Compounds Supported by <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis><Emphasis Type="BoldItalic">′</Emphasis>-Dimethylbenzamidinate: Formation of Linear Polymers via Axial Ligation

The reaction between Re₂(DMBA)₄Cl₂ and NaN(CN)₂ resulted in Re₂(DMBA)₄(N(CN)₂)₂ (1a), where DMBA is N,N′-dimethylbenzamidinate. Molecular compounds Re₂(DMBA)₄(ReO₄)₂ (1b) and Re₂(DMBA)₄(OP(O)(OH)Ph)₂ (1c) were obtained through the reactions between Re₂(DMBA)₄(NO₃)₂ and the respective monoanion. The dirhenium(III) coordination polymers [Re₂(DMBA)₄(μ-O,O′-WO₄)·2H₂O]_∞ (2a), [Re₂(DMBA)₄(μ-O,O′-MoO₄)·2H₂O]_∞ (2b), and [Re₂(DMBA)₄(μ-O,O′-1,4-(O₂C)₂C₆H₄)·2H₂O]_∞ (2c) were similarly prepared through slow diffusion of Re₂(DMBA)₄(NO₃)₂ in acetonitrile into aqueous solution containing the respective dianion. All new compounds were characterized with single crystal X-ray diffraction, which revealed the retention of the essential structural features of Re₂(DMBA)₄ unit upon the formation of coordination polymers.