Construction of Cylindrical Nanotubular Materials by Self-Assembly of Co(NCS)2 with Bent-Building Blocks Having Diimidazole Rings

Abstract

Three cylindrical nanotubular supramolecular structures (S1, S2, and S3) were synthesized by self-assembly of Co(NCS)2 with 1,3-diimidazolyl benzene (L1), 1,2-diimidazolyl benzene (L2), or 2,6-diimidazolyl pyridine (L3), respectively. They all showed similar top views. Columnar packing or assembly of helices was used to explain the construction of tubular materials with bent ligands. The supramolecular material, S1, derived from L1 was a tubular structure based on columnar packing, and others formed from L2 or L3 were similar structures based on the assembly of helices and were a rare example of Meso-helical architectures. These three tubular materials showed interesting 3-D-packing features because of various π−π interactions between 2-D supramolecules. The free heteroatom, nitrogen, in L3 plays an important role in determining the supramolecular structures. The structures show very high thermal stability up to 291 °C for Co(NCS)2(L1)2, 300 °C for Co(NCS)2(L2)2, and 256 °C for Co(NCS)2(L3)2, respectively. Crystal data for the three structures: Co(NCS)2(L1)2, monoclinic, C2/m, a = 7.403(1) Å, b = 17.561(1) Å, c = 10.275(1) Å, β = 107.201(4)°, V = 1276.0(2) Å3, Z = 4; Co(NCS)2(L2)2, orthorhombic, Cmca, a = 7.868(1) Å, b = 18.614(1) Å, c = 7.794(1) A, V = 2592.2(4) Å3, Z = 8; Co(NCS)2(L3)2, monoclinic, P21/n, a = 11.1230(1) Å, b = 9.2170(1) Å, c = 12.8680(1) Å, β = 95.967(2)°, V = 1312.1(2) Å3, Z = 4.