ABSTRACT
The photophysical processes in a series of isocyano Re(I) phenanthroline complexes {[Re(CNR)n (CO)4-n (phen)](PF6 ); n=2, 3, 4, R=2,6-(i Pr)2 C6 H3 - or t Bu- (n=2)} in acetonitrile have been studied by resonance Raman spectroscopy, transient resonance Raman spectroscopy, and femtosecond / nanosecond transient spectroscopy to elucidate the nature of their electronic transitions and emissive excited state(s). The kinetics of the intersystem crossing, vibrational relaxation and radiative decay of the metal-to-ligand charge transfer {MLCT [dπ(Re)âπ*(phen)]} excited state have also been determined.
ABSTRACT
A series of polynuclear metal complexes, [Cu2(L1)(PPh3)4](ClO4)2 (1), [Cu3(L2)(PPh3)6](ClO4) (2), [Cu3(L3)(PPh3)6] (3), [Ag2(L1)(PPh3)4](BF4)2 (4), [Ag4(L2)2(PPh3)6] (5) and [Ag3(L3)(PPh3)5] (6), have been obtained from the reactions of the highly conjugated bridging ligands 2,3-bis(2-pyridyl)pyrazine (L1), 2,3-bis(2-tetrazoyl)pyrazine (H2L2) and 2,3-bis(2-tetrazoyl)imidazole (H3L3) with [Cu(MeCN)4]ClO4 and AgBF4, respectively. Their crystal structures have been determined by X-ray crystallography and their photophysical properties have been investigated in detail. Complexes 1 and 3 show photoluminescence in CH2Cl2 solution, while all the complexes exhibit obvious luminescence in the solid state; detailed photophysical studies and density functional theory calculations of these complexes have revealed that their lowest energy absorptions and emissions are predominantly derived from either metal-to-ligand charge-transfer (MLCT) or intraligand (IL) excited states.
ABSTRACT
We demonstrate a method for the synthesis of NixNb1-xO catalysts with sponge-like and fold-like nanostructures. By varying the Nb:Ni ratio, a series of NixNb1-xO nanoparticles with different atomic compositions (x = 0.03, 0.08, 0.15, and 0.20) have been prepared by chemical precipitation. These NixNb1-xO catalysts are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. The study revealed the sponge-like and fold-like appearance of Ni0.97Nb0.03O and Ni0.92Nb0.08O on the NiO surface, and the larger surface area of these NixNb1-xO catalysts, compared with the bulk NiO. Maximum surface area of 173 m2/g can be obtained for Ni0.92Nb0.08O catalysts. In addition, the catalytic hydroconversion of lignin-derived compounds using the synthesized Ni0.92Nb0.08O catalysts have been investigated.
Subject(s)
Nickel/chemistry , Oxides/chemical synthesis , Catalysis , Nanostructures/chemistry , Niobium/chemistry , Oxides/chemistryABSTRACT
Luminescent porous coordination polymers, cage-containing chains [Pb5(L1)6(N3)2(OH)2]n (1) and 1-D double helical chains [Pb(L2)(N3)]n (2) with 1-D channels were prepared by solvothermal reactions. These polymers can take up metal ions and induce different luminescence responses depending on the metal ions.
ABSTRACT
A series of luminescent isocyanorhenium(I) complexes with chelating acyclic diaminocarbene ligands (N^C) has been synthesized and characterized. Two of these carbene complexes have also been structurally characterized by X-ray crystallography. These complexes show blue-to-red phosphorescence, with the emission maxima not only considerably varied with a change in the number of ancillary isocyanide ligands but also extremely sensitive to the electronic and steric nature of the substituents on the acyclic diaminocarbene ligand. A detailed study with the support of density functional theory calculations revealed that the lowest-energy absorption and phosphorescence of these complexes in a degassed CH2Cl2 solution are derived from the predominantly metal-to-ligand charge-transfer [dπ(Re) â π*(N^C)] excited state. The unprecedented anion-binding and CO2-capturing properties of the acyclic diaminocarbene have also been described.
ABSTRACT
A new series of cyclometalated iridium(III) complexes with isocyanoborate ligands [Ir(R2ppy)2(L)(CNBR'3)] (R = H or F; L = CNC6H4Cl-4 or PPh3; R' = Ph, C6F5 or C6H4Cl-4), [Ir(biqb)(ppy)(CNBR''3)] (R'' = C6F5 or C6H4Cl-4) and {Ir(ppy)2(CN)n[CNB(C6F5)3]2-n}(-) (n = 0 or 1) have been synthesized and characterized. Three of these complexes have also been structurally characterized by X-ray crystallography. The photophysical and electrochemical properties of these complexes have been investigated. The effects of isocyanoborate ligands on the luminescence properties of these iridium(III) complexes are also described.
ABSTRACT
A new series of neutral isocyanoborato rhenium(I) diimine complexes [Re(CO)3 (N^N)(CNBR3 )], where N^N=bpy, 4,4'-Me2 bpy, phen, 4,7-Me2 phen, 2,9-Me2 phen, 3,4,7,8-Me4 phen; R=C6 F5 , C6 H5 , Cl, 4-ClC6 H4 , 3,5-(CF3 )2 C6 H3 , with various isocyanoborate and diimine ligands of diverse electronic and steric nature have been synthesized and characterized. The X-ray crystal structures of six complexes have also been determined. These complexes displayed intense bluish green to yellow phosphorescence at room temperature in dichloromethane solution. The photophysical and electrochemical properties of these complexes had been investigated. To elucidate the electronic structures and transitions of these complexes, DFT and TD-DFT calculations have been performed, which revealed that the lowest-energy electronic transition associated with these complexes originates from a mixture of MLCT [dπ(Re)âπ*(N^N)] and LLCT [π(CNBR3 )âπ*(N^N)] transitions.
ABSTRACT
A series of pyridine- and bipyridine-containing leucotriarylmethane ligands has been successfully synthesised and incorporated into tricarbonyl rhenium(I) diimine complexes. The X-ray crystal structures of two of the complexes have also been determined. The photoreactivity, photophysical and electrochemical properties of these ligands and their rhenium complexes were investigated. The photo-ionisation of the leucotriarylmethanes in the free ligands and their metal complexes and the subsequent change in absorption properties were also studied. Additionally, the electrochemistry of these ligands and complexes were investigated.