An X-ray and 13C CP/MAS NMR study of C,C-linked bipyrazoles and bispyrazolylmethanes

• Published in: Spectrochimica acta. Part A: Molecular spectroscopy 1994, Vol.50 (4), p.727-734
• Main Authors: Monge, Maria Angeles, Pu̧ebla, Enrique Gutierrez, Elguero, Jose, Toiron, Catherine, Meutermans, Wim, Sobrados, Isabel
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Heterocyclic compounds; Organic compounds; Physics; Single-crystal and powder diffraction; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; X-ray diffraction and scattering
• ISSN: 0584-8539
• DOI: 10.1016/0584-8539(94)80010-3

4,4′-Methylene-bispyrazole ( 1) crystallizes in the P2 1/ n space group with Z = 4, a = 5.4199(8) Å, b = 16.194(6) Å, c = 8.381(5) Å, β = 98.18(5)°. 4,4′-Methylene-bis (3,5-dimethylpyrazole) ( 2) crystallizes in the Pbca space group with Z = 8, a = 8.350(3) Å, b = 16.078(3) Å and c = 17.154(5) Å. Finally, 3,3′-bipyrazole ( 4) crystallizes in the P2 1/ n space group with Z = 2, a = 5.465(2) Å, b = 5.491(3) Å, c = 10.058(4) Å and sol; = 92.88(2)°. The packing adopted by molecules 1 and 2 is related to the disposition of the pyrazole rings. In compound 4, all the molecules are joined to their neighbors by two double hydrogen bond systems forming zigzag chains. Using solid state 13C NMR spectroscopy, no dynamic proton transfer was observed in these crystals, and not on those of 3,5,3′,5′-tetramethyl-4,4′-bipyrazole ( 3) either.