Low Barrier Hydrogen Bond (LBHB) Interactions in the Solid State Crystal Structures of Phthalate Salts Based on Trisubstituted Guanidinium Cations

The hydrogen phthalate salt N, N , N - tricyclohexylguanidinium hydrogen phthalate{C(HNcyclohexyl)3}^+HPHT-(1) was prepared and the structure was determined by X-raydiffraction analysis and characterized by elemental analysis, NMR and IR spectroscopy. Thehydrogen-bonding interactions of this colorless solid have been explored in order to examine the potential of intermolecular and intramolecular interactions and their influence on the extended structure that was observed. Compound 1 crystallizes in the monoclinic space group P2(1)/n, with a = 10.6270 (13) Ă, b = 16.809 (2) Ă, c = 15.1657 (18) Ă and β = 102.978 (2)°; Z = 4. The crystal data indicate that the anion displayed a characteristic intramolecular, low barrierhydrogen bond (LBHB) (S(7) motif) via O-H…O interaction. The primary structure combines two cyclic associations, a 16-membered ring (R4^4(16) notation) and a large 46-membered ring (R4^4(46) notation), through N-H…O hydrogen-bonding interactions. The structure of 1 iscompared with the analogue salts N, N , N - triisopropylguanidinium phthalate 2 and N, N , N -triisopropylguanidinium hydrogen maleate 3.