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Download fileCu(I) Complexes of 3,3‘-Polymethylene Bridged Derivatives of 2,2‘-Bi-1,10-Phenanthroline
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posted on 2003-09-16, 00:00 authored by Elvira C. Riesgo, Yi-Zhen Hu, Randolph P. ThummelA series of 3,3‘-polymethylene-2,2‘-bi-1,10-phenanthrolines coordinate with Cu(I) to form dinuclear complexes
[(CuL)2]2+. As the 3,3‘-bridge is lengthened from two to four carbons, the ligand becomes more twisted about the
2,2‘-bond, favoring dinuclear coordination. The distance between the two copper atoms varies from 2.92 Å for the
dimethylene-bridged system to 3.59 Å for the tetramethylene bridge. Favorable π-stacking interactions occur between
opposing ligands and promote complex formation. Competition experiments indicate that self-recognition is important
and only homoleptic complexes are observed. Under equilibrium conditions, formation of the tetramethylene-bridged
complex appears to be the most favored while the dimethylene-bridged system is least favored. The intensity of
the long wavelength metal−ligand charge-transfer absorption band decreases as the 3,3‘-bridge is shortened.
Interaction between the two copper centers is evidenced by a splitting of the oxidation wave, and this splitting
increases as the Cu−Cu distance is decreased.