STRUCTURE, EPR AND UV-VIS AND IR SPECTROELECTROCHEMISTRY OF REVERSIBLY REDUCIBLE COMPOUNDS [(C(5)ME(5))IRCL(L)](PF6), L=1,3-DIMETHYLLUMAZINE OR 1,3-DIMETHYLALLOXAZINE
O. Heilmann et al., STRUCTURE, EPR AND UV-VIS AND IR SPECTROELECTROCHEMISTRY OF REVERSIBLY REDUCIBLE COMPOUNDS [(C(5)ME(5))IRCL(L)](PF6), L=1,3-DIMETHYLLUMAZINE OR 1,3-DIMETHYLALLOXAZINE, Journal of the Chemical Society. Faraday transactions, 92(21), 1996, pp. 4233-4238
Citations number
68
Categorie Soggetti
Chemistry Physical","Physics, Atomic, Molecular & Chemical
In an attempt to model possible metal-pterin or metaI-flavin ligand in
teractions the title compounds have been prepared and their structure,
spectroscopy and spectroelectrochemistry (EPR, IR, UV-VIS) compared w
ith results for the corresponding rhodium analogues. The X-ray crystal
structure of [(C(5)Me(5))IrCl(DML)](PF6), DML = 1,3-dimethyllumazine,
shows O-4/N-5 chelate coordination of iridium with a shorter bond to
the nitrogen centre [2.103(4) vs. 2.186(3) Angstrom], a slightly more
unsymmetrical situation than that found in the rhodium analogue. Elect
rochemical studies (cyclic voltammetry, polarography) showed largely r
eversible one-electron reduction processes to radical species [(C(5)Me
(5))IrCl(L)](.) which allowed us to investigate the EPR, IR and UV-VIS
response to the reduction. Although the EPR spectra of the iridium co
mpounds remained unresolved, the low g factors (g < 2) and particular
line shapes revealed small but significant contributions from the heav
y-metal centre. Long-wavelength absorptions at ca. 600 nm and low-ener
gy shifts of the carbonyl stretching bands confirm the formulation [(C
(5)Me(5))(IrCl)-Cl-III(L(-1))](.) for the electronic situation.