A series of heteroleptic bis(tridentate) ruthenium(II) complexes, each bearing a substituted 2,2':6',2″-terpyridine (terpy) ligand, is characterized by room temperature microsecond excited-state lifetimes. This observation is a consequence of the strongly σ-donating and weakly π-accepting tridentate carbene ligand, 2',6'-bis(1-mesityl-3-methyl-1,2,3-triazol-4-yl-5-idene)pyridine (C^N^C), adjacent to the terpy maintaining a large separation between the ligand field and metal-to-ligand charge transfer (MLCT) states while also preserving a large (3)MLCT energy. The observed lifetimes are the highest documented lifetimes for unimolecular ruthenium(II) complexes and are four orders in magnitude higher than that associated with [Ru(terpy)(2)](2+).
[Show abstract][Hide abstract] ABSTRACT: The ligands 1-(cyclohexyl)-4-(2-pyridyl)-1,2,3-triazole (), 1-(2,6-diisopropylphenyl)-4-(2-pyridyl)-1,2,3-triazole (), 1-(4-butoxyphenyl)-4-(2-pyridyl)-1,2,3-triazole () and 1-(methyl)-4-(2-pyridyl)-1,2,3-triazole () were synthesized by the Cu(i) catalyzed "Click" reaction between 2-pyridylacetylene and the corresponding azides. The ligands were then reacted with NiBr(2)·3H(2)O to generate the complexes ()(2)NiBr(2) (), ()(2)NiBr(2) (), ()(2)NiBr(2) () and ()(2)NiBr(2) (). Structural characterization of confirmed the mononuclear and distorted octahedral environment around the Ni(ii) center, with the pyridyl-triazole ligands coordinating in a bis-chelating fashion. Bond length analysis inside the 1,2,3-triazole ring shows a short N[double bond, length as m-dash]N double bond that is flanked by two longer C-N and N-N bonds pointing to the existence of "azo" character in the ring. The highly polar five-membered 1,2,3-triazole ring makes its C-H bond acidic, and these bonds participate in an extended weak intermolecular C-HBr interactions with the Br-groups of neighboring molecules, resulting in a 3-D network. The nickel complexes with these "Click" ligands were tested as pre-catalysts for ethylene oligomerization, and the complexes showed moderate activity in that reaction with good selectivity towards C4 oligomers.
[Show abstract][Hide abstract] ABSTRACT: A super pyrazolate: Deprotonation of the flanking hydrogen of metal complexes of mesoionic carbenes (MICs) offers a simple and general route for the preparation of bimetallic complexes of a 1,2-dihapto anionic dicarbene ligand that is isoelectronic with widely used pyrazolate ligands, while conferring greater electron donation and stronger ML bonds.
Chemistry - A European Journal 11/2012; 18(46). DOI:10.1002/chem.201202862 · 5.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Integrating a matched organic chromophore and a Ru(ii) complex with optimized tridentate polypyridine ligands instils reversible electronic energy transfer giving an unusually long room temperature luminescence lifetime (42 [small mu ]s) without compromising the emission quantum yield.
Chemical Communications 09/2013; 49(80-80):9110-9112. DOI:10.1039/C3CC45387A · 6.83 Impact Factor
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