1H nuclear magnetic resonance study of the association between 1,5-dialkyl-1,5-dihydro-1,5-benzodiazepine-2,4-diones and the shift reagent Eu(fod)3

Abstract

By observing the shifts of the ¹H n.m.r. signals of 1,5-dihydro-1,5-benzodiazepine-2,4-diones induced by Eu(fod)₃ and simulating them with the aid of the computer program TWOCEN, evidence has been found for competition in Eu co-ordination by the two carbonyl groups, involving two-site metal binding at each oxygen atom. Geometric parameters calculated for the complexes under study suggest that Eu(fod)₃ becomes mostly involved in a type of bidentate binding to both carbonyl groups unless a substituent is present at C-3. An electronegative group bonded to C-7, essential for optimal activity of benzodiazepine derivatives, appears to affect slightly the relative complexing ability of the two oxygen atoms. The preferred orientations of the N-substituents have also been deduced, by the computer-assisted LIS method.