Reaction of 1Н,2Н,3Н,4Н-pyrido[4,3-d]pyrimidinium bromide derivatives with molecular iodine: Comparative structure and spectroscopic analysis

Abstract

Abstract New salts C 27 H 22 N 3 O 2 BrI 2 ( 1 ) and C 27 H 19 N 3 O 2 Br 4 I 2 ·2CHCl 3 ·2H 2 O ( 2 ) were synthesized by the iodination of derivatives of 1,3-dimethyl-2,4-dioxo-5,6,7-R-1Н,2Н,3Н,4Н-pyrido[4,3- d ]pyrimidinium bromide (R = phenyl ( 1a ), p -bromphenyl ( 2a )) with an equimolar amount of iodine. The positive values of enthalpy (Δ H ) and entropy (Δ S ) indicate that the complexation of organic bromide and iodine molecule in chloroform solution is mainly entropically driven. The molecular and crystal structures ( 1 ) and ( 2 ) are studied by X-ray diffraction analysis. The structure of diiodinebromide 1 is composed of separate almost liner BrI 2 - and 1,3-dimethyl-2,4-dioxo-5,6,7-thriphenyl-1Н,2Н,3Н,4Н-pyrido[4,3- d ]pyrimidinium cation. The crystal structure 2 is built up of alternate layers of ( C 27 H 19 N 3 O 2 Br 3 + ) ( I 3 - ) ( A ) and (Br 2 I − )(СHСl 3 ) ( B ), connected to each other by hydrogen bonds Br ( Br 2 I - ) ⋯ H ( C 27 H 19 N 3 O 2 Br 3 + ) . The formation of the ions I 3 - and Br 2 I − occurs via the disproportionation of I 2 Br − under the action of solvent on C 27 H 19 N 3 O 2 Br 4 I 2 ·2CHCl 3 ·2H 2 O ( 2 ) crystallization.