Redox and spin state control of Co(II) and Fe(II) N-heterocyclic complexes

被引:55
作者
Ayers, T
Scott, S
Goins, J
Caylor, N
Hathcock, D
Slattery, SJ [1 ]
Jameson, DL
机构
[1] State Univ W Georgia, Dept Chem, Carrollton, GA 30118 USA
[2] Gettysburg Coll, Dept Chem, Gettysburg, PA 17325 USA
基金
美国国家科学基金会;
关键词
electrochemistry; cobalt complexes; iron complexes; N-heterocyclic ligand complexes;
D O I
10.1016/S0020-1693(00)00179-1
中图分类号
O61 [无机化学];
学科分类号
070301 ; 081704 ;
摘要
Two series of complexes with the general formulas [Co(L)(2)](2+) and [Fe(L)(2)](2+), where L represents the tridentating ligands 2,2':6';2 "-terpyridine (L-1), 6-(N-pyrazolyl)-2,2'-bipyridine (L-2); and 2,6-bis(N-pyrazolyl)pyridine (L-3), were prepared and characterized. The electronic properties of both series of compounds were investigated as a function of stepwise variation in coordinated pyridines relative to pyrazoles. In the cobalt series, the Co(III/II) redox potential measured an average anodic shift of 0.16 V for each pyridine coordination site replaced by pyrazole, while only a slight shift was observed for the Fe(III/II) couple. Solution magnetic susceptibility measurements showed a general shift toward a high-spin ground state as pyridine was replaced by coordinated pyrazoles. The cobalt series exhibited a mu(eff) of 3.2 B.M. for bis-terpy (L-1) which is close to the spin crossover, while the mu(eff) for [Co(L-2)(2)](2+) and [Co(L-3)(2)](2+) were measured at 4.5 and 4.6 B.M., respectively. For the iron series, [Fe(L-1)(2)](2+) and Fe(L-2)(2)](2+) exhibited a stable diamagnetic low-spin state; however, [Fe(L-3)(2)](2+) measured a mu(eff) of 4.6 B.M. which implies a spin equilibrium that is predominantly high-spin with possible low-spin contribution. The observed redox and spin state regulation correlate with the weaker sigma-donor and pi-acceptor properties of coordinated pyrazole relative to pyridine. (C) 2000 Elsevier Science S.A. All rights reserved.
引用
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页码:7 / 12
页数:6
相关论文
共 22 条
[11]  
JAMESON DL, 1989, INORG CHEM, V28, P4311
[12]  
Judge J. S., 1967, INORG CHIM ACTA, V1, P68
[13]   RU(II) POLYPYRIDINE COMPLEXES - PHOTOPHYSICS, PHOTOCHEMISTRY, ELECTROCHEMISTRY, AND CHEMI-LUMINESCENCE [J].
JURIS, A ;
BALZANI, V ;
BARIGELLETTI, F ;
CAMPAGNA, S ;
BELSER, P ;
VONZELEWSKY, A .
COORDINATION CHEMISTRY REVIEWS, 1988, 84 :85-277
[14]   Variable-temperature studies of laser-initiated T-5(2)->(1)A(1) intersystem crossing in spin-crossover complexes: Empirical correlations between activation parameters and ligand structure in a series of polypyridyl ferrous complexes [J].
McCusker, JK ;
Rheingold, AL ;
Hendrickson, DN .
INORGANIC CHEMISTRY, 1996, 35 (07) :2100-2112
[15]   DESIGNER MAGNETS [J].
MILLER, JS ;
EPSTEIN, AJ .
CHEMICAL & ENGINEERING NEWS, 1995, 73 (40) :30-41
[16]  
SAWYER T, 1976, EXPT ELECTROCHEMISTR
[17]   UTILIZING THE EVANS METHOD WITH A SUPERCONDUCTING NMR SPECTROMETER IN THE UNDERGRADUATE LABORATORY [J].
SCHUBERT, EM .
JOURNAL OF CHEMICAL EDUCATION, 1992, 69 (01) :62-62
[18]   BIS(4,4'-BIS(DIETHYLAMINO)-2,2'-BIPYRIDINE)DICHLORORUTHENIUM(III) - A NEW STARTING MATERIAL FOR RUTHENIUM POLYPYRIDYL COMPLEXES EXHIBITING LOW REDOX POTENTIALS [J].
SLATTERY, SJ ;
GOKALDAS, N ;
MICK, T ;
GOLDSBY, KA .
INORGANIC CHEMISTRY, 1994, 33 (17) :3621-3624
[19]  
SLATTERY SJ, IN PRESS J CHEM S DA
[20]  
WEAST RC, 1982, CRC HDB CHEM PHYSICS