Di- and Triammonium Salts of Carbamoyldicyanomethanide, C(CN)₂(CONH₂)⁻: Layered Organic Architectures

Abstract

Layered organic structures, containing robust hydrogen-bonded anionic tapes bridged by di- and triammonium cations, have been synthesized and structurally characterized. Salts of the carbamoyldicyanomethanide (cdm) anion, C(CN)2(CONH2)−, using H3N(CH2)nNH3 cations (n = 2, 3, or 4) display layered structures containing one-dimensional (1D) hydrogen-bonded chains of cdm. The structure of (H3N(CH2)2NH3)(cdm)2 (1) forms a bilayer structure with the cation bridging, through charge-assissted hydrogen bonds, between parallel anionic ribbons containing two different synthons. The longer cation in (H3N(CH2)3NH3)(cdm)2 (2) results in a structure containing parallel anionic layers with cationic pillars running through them. The layers in 2 contain different hydrogen bonded tapes with R22(8) and R22(16) ring synthons which are also observed in the structure of (H3N(CH2)4NH3)(cdm)2 (3). Despite the differing length of the cation in 2 and 3, the distances between the layers are remarkably similar; however, the extra degree of flexibility in the (CH2)4-based cation results in the relative orientation of the layers differing. The structure of the triammonium salt (H3N(CH2)2NH2(CH2)2NH3)(cdm)3 (4) contains hydrogen-bonded anionic sheets through which the linear cations pass with each cation interacting with five different anionic layers, compared to three in the structures of 2 and 3