Different patterns of supramolecular assembly in constitutionally similar 6-arylimidazo[2,1-b][1,3,4]thiadiazoles.

Four imidazo[2,1-b][1,3,4]thiadiazoles containing a simply-substituted 6-aryl group have been synthesized by reaction of 2-amino-1,3,4-thiadiazoles with bromoacetylarenes using microwave irradiation and brief reaction times. 6-(2-Chlorophenyl)imidazo[2,1-b][1,3,4]thiadiazole, C(10)H(6)ClN(3)S, (I), 6-(2-chlorophenyl)-2-methylimidazo[2,1-b][1,3,4]thiadiazole, C(11)H(8)ClN(3)S, (II), 6-(3,4-dichlorophenyl)imidazo[2,1-b][1,3,4]thiadiazole, C(10)H(5)Cl(2)N(3)S, (III), and 6-(4-fluoro-3-methoxyphenyl)-2-methylimidazo[2,1-b][1,3,4]thiadiazole, C(12)H(10)FN(3)OS, (IV), crystallize with Z' values of 2, 1, 1 and 2 respectively. The molecular skeletons are all nearly planar and the dihedral angles between the imidazole and aryl rings are 1.51 (8) and 7.28 (8)° in (I), 9.65 (7)° in (II), 10.44 (8)° in (III), and 1.05 (8) and 7.21 (8)° in (IV). The molecules in (I) are linked by three independent C-H...N hydrogen bonds to form ribbons containing alternating R2(2)(8) and R4(4)(18) rings, and these ribbons are linked into a three-dimensional array by three independent π-stacking interactions. Both (II) and (III) contain centrosymmetric dimers formed by π-stacking interactions but hydrogen bonds are absent, and the molecules of (IV) are linked into centrosymmetric R2(2)(8) dimers by C-H...N hydrogen bonds. Comparisons are made with a number of related compounds.

[1]  K. Alagawadi,et al.  Novel imidazo[2,1-b][1,3,4]thiadiazole carrying rhodanine-3-acetic acid as potential antitubercular agents. , 2012, Bioorganic & medicinal chemistry letters.

[2]  Frank H. Allen,et al.  Hydrogen-bond directionality at the donor H atom—analysis of interaction energies and database statistics , 2009 .

[3]  Ravi S. Lamani,et al.  Synthesis and antimicrobial studies of novel methylene bridged benzisoxazolyl imidazo[2,1-b][1,3,4]thiadiazole derivatives. , 2009, European journal of medicinal chemistry.

[4]  M. Kulkarni,et al.  Synthesis and anti-inflammatory evaluation of methylene bridged benzofuranyl imidazo[2,1-b][1,3,4]thiadiazoles. , 2008, European journal of medicinal chemistry.

[5]  M. Noolvi,et al.  Synthesis and anti-tubercular activity of a series of 2-sulfonamido/trifluoromethyl-6-substituted imidazo[2,1-b]-1,3,4-thiadiazole derivatives. , 2004, Bioorganic & medicinal chemistry.

[6]  Raymond E. Davis,et al.  Patterns in Hydrogen Bonding: Functionality and Graph Set Analysis in Crystals , 1995 .

[7]  S. Christensen,et al.  ON THE STRUCTURE OF GASEOUS ANISOLE , 1974 .

[8]  R. J. Myers,et al.  Microwave Spectra, Dipole Moment, and Barrier to Internal Rotation of CH3NO2 and CD3NO2 , 1956 .

[9]  E. B. Wilson,et al.  Microwave Spectrum and Barrier to Internal Rotation in CH3BF2 , 1955 .

[10]  M. Noolvi,et al.  Synthesis and biological evaluation of 2-trifluoromethyl/sulfonamido-5,6-diaryl substituted imidazo[2,1-b]-1,3,4-thiadiazoles: a novel class of cyclooxygenase-2 inhibitors. , 2008, Bioorganic & medicinal chemistry.

[11]  G. Sheldrick.  A short history of SHELX. , 2008, Acta crystallographica. Section A, Foundations of crystallography.

[12]  Katsumi Kimura,et al.  Structures of Dimethyl Ether and Methyl Alcohol , 1959 .