Crystal engineering of urea α-network via I⋯O < inf > 2 < /inf > N synthon and design of SHG active crystal N-4-iodophenyl-N′-4′-nitrophenylurea

Abstract

Crystalline nitrodiphenyl ureas adopt the N-H⋯O tape α-network only when stabilization accrues from the I⋯O2N or C≡C-H⋯O2N synthon, otherwise the urea⋯nitro motif is preferred; soft, weak interactions can direct polar self-assembly in strong N-H⋯O hydrogen-bonded crystals. © 2004 Royal Society of Chemistry.