Facile Synthesis and Structures of Cyclic Triimidazole and Its Boric Acid Adduct

High Resolution Image Download MS PowerPoint Slide Cyclic triimidazole, C 9 H 6 N 6 ( 1 ), was prepared by thermolysis of the easily prepared copper imidazolate framework solid, Cu(C 3 H 3 N 2 ) 2 ( 2 ), providing a convenient route to this potentially useful tecton for molecular design. Anhydrous 1 and a hydrate, 1 ·0.5H 2 O, were characterized by single-crystal X-ray diffraction. Hydrate 1· 0.5H 2 O contains two crystallographically independent 1 molecules. Supramolecular structures of 1 and 1· 0.5H 2 O feature stacking arrangements in which the 1 molecule deviates from idealized geometry. A 3-fold H-bond acceptor 1 forms an adduct with boric acid, 1· B(OH) 3, which was also structurally characterized. This adduct is composed of hydrogen-bonded sheets of 1 and B(OH) 3 molecules with sheet interplanar separations of 3.175(4) Å and B(OH) 3 boron atoms positioned above and below the centroids of 1 in adjacent sheets. Unlike 1 and its hydrate, 1· B(OH) 3 contains 1 molecules that display crystallographically required D 3 h symmetry. Anhydrous 1 crystallizes in the triclinic system, space group P 1̅, with a = 7.2138(12), b = 8.3667(15), c = 8.8361(13) Å, α = 99.826(13), β = 113.825(10), γ = 110.721(11)°, V = 424.55(12) Å 3, Z = 2; 1 2 · H 2 O (or 1· 0.5H 2 O), triclinic, P 1̅, a = 7.5608(3), b = 7.5669(5), c = 15.8436(8) Å, α = 84.504(3), β = 81.269(3), γ = 87.038(3)°, V = 891.18(8) Å 3, Z = 2; 1· B(OH) 3, trigonal, P 3̅, a = 10.1186(3), b = 10.1186(3), c = 6.3488(4) Å, α = 90, β = 90, γ = 120°, V = 562.94(4) Å 3, Z = 2.