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A redox-active diamine ligand, 4,4'-bis(di-p-anisylamino)-2,2'-bipyridine (NNbpy), has been prepared. Electrochemical and spectroscopic studies suggest that little electronic coupling is present between two amine groups in NNbpy. After chelation with Ru(bpy)2 (bpy is 2,2'-bipyridine), the resulting complex displays two N·+/0 processes at +1.02 and +1.16 V versus Ag/AgCl. In the mixed-valent state, rich near-infrared absorptions have been observed, which are believed to consist of multiple metal-to-ligand charge transfer and intervalence charge transfer transitions in the low-energy region. These results suggest that the amine-amine electronic coupling has been enhanced by chelation with Ru(bpy)2. In contrast, no efficient electronic coupling can be realized by chelation with Ir(ppy)2 (ppy is 2'-phenylpyridine) or Re(CO)3Cl. A ruthenium ion-mediated electron transfer mechanism, instead of through-space coupling, has been proposed to explain this phenomenon. For the purpose of comparison, a monoamine-substituted bpy ligand and corresponding Ru(bpy)2 complex have been synthesized and studied. In addition, EPR, DFT, and TDDFT studies have been performed to complement the experimental results [ABSTRACT FROM AUTHOR]

A series of biscyclometalated ruthenium complexes bridged by the title ligand were prepared by either an oxidative dimerization of corresponding monometallic complexes or treatment of the bridging ligand with Ru(L)Cl3 (L = capping ligand). The electronic properties of these complexes were examined by electrochemical and spectroscopic analysis and DFT/TDDFT calculations. The degree of metal-metal electronic coupling of these complexes was estimated on the basis of intervalence charge-transfer transition analysis of corresponding mixed-valent complexes. These studies indicated that the electronic coupling was strongly dependent on the electronic nature of the terminal ligands. A hole-transfer superexchange mechanism was used to understand the underlying electron-transfer processes. [ABSTRACT FROM AUTHOR]

A dimetallic biscyclometalated ruthenium complex, [(bpy)2Ru(dpb)Ru(bpy)2]2+ (bpy = 2,2'-bipyridine; dpb = 1,4-di-2-pyridylbenzene), with a tris-bidentate coordination mode has been prepared. The electronic properties of this complex were studied by electrochemical and spectroscopic analysis and DFT/TDDFT calculations on both rac and meso isomers. Complex [(bpy)2Ru(dpb)Ru(bpy)2]2+ has a similar 1,4-benzenedicyclometalated ruthenium (Ru-phenyl-Ru) structural component with a previously reported bis-tridentate complex, [(tpy)Ru(tpb)Ru(tpy)]2+ (tpy = 2,2';6',2?-terpyridine; tpb = 1,2,4,5-tetra-2-pyridylbenzene). The charge delocalizations of these complexes across the Ru-phenyl-Ru array were investigated and compared by studying the corresponding one-electron-oxidized species, generated by chemical oxidation or electrochemical electrolysis, with DFT/TDDFT calculations and spectroscopic and EPR analysis. These studies indicate that both [(bpy)2Ru(dpb)Ru(bpy)2]3+ and [(tpy)Ru(tpb)Ru(tpy)]3+ are fully delocalized systems. However, the coordination mode of the metal component plays an important role in influencing their electronic properties. [ABSTRACT FROM AUTHOR]

A series of asymmetrical bis-tridentate cyclometalated complexes including [Ru(Mebib)(Mebip)]+, [Ru(Mebip)(dpb)]+, [Ru(Mebip)(Medpb)]+, and [Ru(Mebib)(tpy)]+ and two bis-tridentate noncyclometalated complexes [Ru(Mebip)2]2+ and [Ru(Mebip)(tpy)]2+ were prepared and characterized, where Mebib is bis(N-methylbenzimidazolyl)benzene, Mebip is bis(N-methylbenzimidazolyl)pyridine, dpb is 1,3-di-2-pyridylbenzene, Medpb is 4,6-dimethyl-1,3-di-2-pyridylbenzene, and tpy is 2,2′:6′,2″-terpyridine. The solid-state structure of [Ru(Mebip)(Medpb)]+ is studied by X-ray crystallographic analysis. The electrochemical and spectroscopic properties of these ruthenium complexes were studied and compared with those of known complexes [Ru(tpy)(dpb)]+ and [Ru(tpy)2]2+. The change of the supporting ligands and coordination environment allows progressive modulation of the metal-associated redox potentials (RuII/III) from +0.26 to +1.32 V vs Ag/AgCl. The introduction of a ruthenium cyclometalated bond in these complexes results in a significant negative potential shift. The RuII/III potentials of these complexes were analyzed on the basis of Lever’s electrochemical parameters (EL). Density functional theory (DFT) and time-dependent DFT calculations were carried out to elucidate the electronic structures and spectroscopic spectra of complexes with Mebib or Mebip ligands. [ABSTRACT FROM AUTHOR]

A new bridging ligand 1,3,6,8-tetrakis(1-butyl-1H-1,2,3-triazol-4-yl)pyrene (ttapyr) was designed and synthesized by "click" chemistry. This ligand was used to construct a linear dimetallic biscyclometalated Ru(II) complex [(tpy)Ru(ttapyr)Ru(tpy)]2+ and a monometallic complex [(tpy)Ru(ttapyr)]+, where tpy is 2,2′:62′,22″-terpyridine. The electronic properties of these complexes were studied and compared by electrochemical and spectroscopic methods with the aid of DFT calculations. One-electron oxidation of [(tpy)Ru(ttapyr)Ru(tpy)]2+ with cerium ammonium nitrate produced a mixed-valent complex [(tpy)Ru(ttapyr)Ru(tpy)]3+. The intramolecular electronic coupling between individual metal centers was quantified by the intervalence charge transfer transition analysis. Mixed-valent complex [(tpy)Ru(ttapyr)Ru(tpy)]3+ exhibits a metal-centered rhombic EPR signal at 77 K with an average g factor of 2.203. [ABSTRACT FROM AUTHOR]

A new luminescent terbium-metal-organic framework [Tb3(L)2(HCOO)(H2O)5]·DMF·4H2O (1) (H4L = 4,4′-(pyridine-3,5-diyl)diisophthalic acid) has been successfully assembled by Tb3+ ions and an undeveloped pyridyl-tetracarboxylate. Compound 1 exhibits a 3D porous (3,8)-connected (4.5²)2(4².512.66.75.8³) topological framework with fascinating 1D open hydrophilic channels decorated by uncoordinated Lewis basic pyridyl nitrogen atoms. In particular, the Tb-MOF (1) can detect Cu2+ ions with high selectivity and sensitivity, and its luminescence is nearly entirely quenched in N,N-dimethylformamide (DMF) solution and biological system. In addition, 1 still has high detection for the trace content of nitromethane with 70 ppm, which suggests that 1 is a promising example of dual functional materials with sensing copper ions and nitromethane. [ABSTRACT FROM AUTHOR]

Cyclometalated diruthenium complexes 1(PF6)2–5(PF6)2 bridged by 1,3,6,8-tetra(pyrid-2-yl)-pyrene have been prepared, with the terminal ligand bis(N-methylbenzimidazolyl)pyridine (1(PF6)2), 4′-di-(p-methoxyphenyl)amino-2,2′:6′,2″-terpyridine (2(PF6)2), 4′-p-methoxyphenyl-2,2′:6′,2″-terpyridine (3(PF6)2), 2,2′:6′,2″-terpyridine (4(PF6)2), and trimethyl-4,4′,4″-tricarboxylate-2,2′:6′,2″-terpyridine (5(PF6)2). The single-crystal X-ray structure of 4(PF6)2 is presented. These complexes show two stepwise anodic redox pairs, and the potentials progressively increase from 1(PF6)2 to 5(PF6)2. Complexes 1(PF6)2–4(PF6)2 have comparable electrochemical potential splitting of 200–210 mV, while complex 5(PF6)2 has a splitting of 170 mV. Upon one-electron oxidation by chemical oxidation or electrolysis, the resulting mixed-valent complexes 13+–53+ display broad and intense absorptions between 1000 and 3000 nm. Complexes 13+ and 23+ show the presence of a higher-energy shoulder band in addition to the main near-infrared absorption band. This shoulder band is less distinguished for 33+–53+. Three-state theory has been used to explain this difference. The one-electron oxidized forms, 13+–53+, exhibit rhombic EPR signals at 77 K with the isotropic g values in the range of 2.18–2.24. Density functional theory (DFT) and time-dependent DFT (TDDFT) computations have been performed on 12+–52+ to characterize their electronic structures and rationalize the absorption spectra in a wide energy range. DFT computations on 13+–53+ show that both ruthenium ions and the bridging ligand have comparable spin densities. TDDFT computations on 13+ and 43+ have been performed to complement the experimental results. [ABSTRACT FROM AUTHOR]

A stable porous carbazole-based luminescent metal-organic framework, NENU-522, was successfully constructed. It is extremely stable in air and acidic/basic aqueous solutions, which provides the strategy for luminescent material encapsulation of Ln3+ ions with tunable luminescence for application in light emission. More importantly, Ln3+@NENU-522 can emit white light by encapsulating different molar ratios of Eu3+ and Ln3+ ions. Additionally, Ln3+@NENU-522 is found to be useful as a fluorescent indicator for the qualitative and quantitative detection of nitroaromatic explosives with different numbers of -NO2 groups, and the concentrations of complete quenching are about 2000, 1000, and 80 ppm for nitrobenzene, 1,3-dinitrobenzene, and 2,4,6-trinitrophenol, respectively. Meanwhile, Ln3+@NENU-522 displays high selectivity and recyclability in the detection of nitroaromatic explosives. [ABSTRACT FROM AUTHOR]

In this work, five novel 2D isostructural Cd(II)-lanthanide(III) heterometallic-organic frameworks [CdCl(L)EuxTby(H2O)(DMA)](NO3)·3DMA (IFMC-36-EuxTby: x = 1, y = 0, IFMC-36-Eu; x = 0.6, y = 0.4, IFMC-36-Eu0.6Tb0.4; x = 0.5, y = 0.5, IFMC-36-Eu0.5Tb0.5; x = 0.4, y = 0.6, IFMC-36-Eu0.4Tb0.6; x = 0, y = 1, IFMC-36-Tb; H3L is 4,4',4"-((2,2',2"-(nitrilotris(methylene))tris(1H-benzo[d]imidazole-2,1-diyl))tris(methylene))tribenzoic acid; IFMC = Institute of Functional Material Chemistry) have been successfully synthesized by taking advantage of different molar ratios of lanthanide(III) (Ln(III)) and metalloligands under solvothermal conditions. Further luminescent measurements indicate that IFMC-36-EuxTby exhibits characteristic sharp emission bands of Eu(III) and Tb(III), and the intensities of red and green can be modulated correspondingly by tuning the ratios of Eu(III) and Tb(III). Particularly, the solvent-dependent luminescent behavior of IFMC-36-Eu shows a potential application in detection of small-molecule pollutant nitrobenzene by significant fluorescence quenching. Furthermore, IFMC-36-Eu displays preeminent anti-interference ability and could be used for sensing in the systems with complicated components. This is the first time that a d-f heterometallic-organic framework can be investigated as a chemical sensor for selective, sensitive, and recyclable detection of nitrobenzene. [ABSTRACT FROM AUTHOR]