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Synthesis and Structures of Substrates for Investigation of Intramolecular Electronic Energy Transfer
Author(s) -
Rubin Mordecai B.,
Migdal Shmuel,
Speiser Shammai,
Kaftory Menahem
Publication year - 1985
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1002/ijch.198500012
Subject(s) - chemistry , intramolecular force , moiety , dihedral angle , molecule , methylene , ring (chemistry) , benzene , acetic anhydride , crystallography , reagent , chromophore , computational chemistry , stereochemistry , hydrogen bond , photochemistry , organic chemistry , catalysis
A series of cyclic α ‐diketones incorporating a benzene ring (ortho, meta or para substituted) have been synthesized for studies of intramolecular energy transfer (intra‐ET). The synthetic method involved acyloin cyclization of the corresponding dicarboxylic acid diesters followed by oxidation with DMSO‐acetic anhydride reagent. All compounds were sufficiently flexible so that, even at temperatures in the range of −120°, only broadened lines were observed in their NMR spectra, consistent with observations on temperature dependence of the intra‐ET process. The structure of one compound (P‐4,4) was established by X‐ray crystallographic analysis and of the remaining compounds by a combination of spectroscopic data and molecular mechanics calculations. The calculated structure of P‐4,4 is essentially identical to the X‐ray structure. In all compounds the methylene chains assume staggered conformations, the dicarbonyl torsion angle aproached 180°, and the molecule folds in such a way that, with one exception, the dicarbonyl moiety lies above (or below) the plane of the benzene ring. Distances between chromophores range from about 3.3 to 5.8 Å.