Collect. Czech. Chem. Commun. 1996, 61, 342-354

trans-4-Stilbenecarboxylatoalkylpentaamminecobalt(III) Perchlorates: Synthesis and Intramolecular Energy Transfer

Cyril Párkányia, Lois Shiow-Chyn Yeh Huangb, Sung Gun Chuc and Alfred T. Jeffries IIId

a Department of Chemistry, Florida Atlantic University, 777 Glades Road, P.O.Box 3091, Boca Raton, Florida 33431-0991, U.S.A.
b Challenger Schools, California Central Office, Campbell, California 95008, U.S.A.
c Research Center, Hercules, Inc., Wilmington, Delaware 19899, U.S.A.
d Organic Chemical Division, Philip A. Hunt Chemical Corporation, Lincoln, Rhode Island 02865, U.S.A.


Three homologs of trans-4-stilbenecarboxylic acid, viz., trans-4-stilbeneacetic acid (18), β-(trans-4-stilbene)propionic acid (19), and γ-(trans-4-stilbene)butyric acid (20) were synthesized and, together with the parent trans-4-stilbenecarboxylic acid, used to obtain the corresponding [ω-(trans-4-stilbene)carboxylatoalkylpentaamminecobalt(III) complexes, [(PhCH=CHC6H4(CH2)nCOO)Co(NH3)5]2+ (1-4), where n = 0, 1, 2, or 3. Fluorescence studies suggest that an intramolecular excitation energy transfer occurs from the first excited singlet state of the ligand to the metal giving rise to a charge-transfer triplet-excited state of the complex, based on the analogy with previous work on complex 1. The efficiency of the energy transfer seems to decrease with increasing number of the methylene groups in the ligand.

Keywords: trans-4-Stilbenecarboxylatoalkylpentaamminecobalt(III) complexes; Energy transfer; Electronic spectra; Fluorescence; LMCT.