Study of the sulfur atom as hydrogen bond acceptor in N(2)-pyridylmethyl-N-arylthioureas

The hydrogen acceptor capability of the sulfur atom in the biologically relevant N-2-pyridylmethyl-N'-arilthioureas was explored. N-2-Pyridylmethyl thioreas were selected to avoid the formation of intramolecular six-membered hydrogen-bonded ring. The compounds studied were N-2-pyridylmethyl-N'-phenylthiourea (1), N-2-pyridylmethyl-N'-2-methoxythiourea (2), N-2-pyridylmethyl-N'-4-methoxyphenylthiourea (3), and N-2-pyridylmethyl-N'-4-bromophenylthiourea (4). 1 crystallizes in the monoclinic space group P2(1)/c, with a = 7.419(1) Angstrom, b = 18.437(2) Angstrom, c = 9.656(1) Angstrom, beta = 106.277(6)degrees, V = 1267.8(3) Angstrom(3), Z = 4.2 crystallizes in the monoclinic space group P2(1)/c, with a = 8.064(2) Angstrom, b = 18.382(7) Angstrom, c = 9.865(5) Angstrom, beta = 97.81(3)degrees, V = 1448.8(11) Angstrom(3), Z = 4.3 crystallizes in the monoclinic space group P2(1)/c, with a = 11.472(1) A, b = 13.520(1) Angstrom, c = 10.088(1) Angstrom, beta = 112.60(1)degrees, V = 1444.5(2) Angstrom(3), Z = 4.4 crystallizes in the triclinic space group P-1, with a = 4.583(3) Angstrom, b = 10.263(3) Angstrom, c = 14.396(3) Angstrom, alpha = 77.92( 2)degrees, beta = 88.55(4)degrees, gamma = 80.02(4)degrees, V = 652.1(5) Angstrom(3), Z = 2. Both thiourea N-H groups form intermolecular hydrogen bonds, one with the thione sulfur atom and the other with the pyridine nitrogen atom but the H-bonding schemes are not the same maybe due to the flexibility of the molecules.