Portal de Periódicos da CAPES

Selenium coronands. A novel conformational pair

1988; NRC Research Press; Volume: 66; Issue: 11 Linguagem: Inglês

10.1139/v88-457

1480-3291

B. Mario Pinto, Blair D. Johnston, Raymond J. Batchelor, Frederick W. B. Einstein, Ian D. Gay,

Crystallography and molecular interactions

The synthesis and characterization of the novel selenium coronands, 1,3,7,9-tetraselenacyclododecane 1a, 1,3,7,9,13,15-hexaselenacyclooctadecane 2a, the corresponding β-gem-dimethyl derivatives 1b, 2b, and 1,5,9,13-tetraselenacyclohexadecane 3, and 1,5,9,13,17,21-hexaselenacyclotetracosane 4 are described. X-ray crystallographic analysis of 1a reveals three independent molecules that exist in two distinct conformations, one molecule having approximate two-fold symmetry together with two molecules (of similar conformation) each having crystallographic [Formula: see text] symmetry. The conformations are denoted as [3333] or [66]. Whereas one resembles that of cyclododecane and tetrathia-12-crown-4 with respect to torsion angles, the other resembles that of tetraoxa-12-crown-4. The solid state CP-MAS 77 Se and 13 C nmr spectra are interpreted in light of the crystallographic information. Crystal structure: formula Se 4 C 8 H 16 ; fw = 428.05; monoclinic, P2 1 /c; Z = 8; a = 15.823(2) Å, b = 5.534(1) Å, c = 27.962(5) Å, β = 92.26(1)°; V = 2446.6 Å 3 ; T = 200 K; R = 0.027 for 2162 observed data (I ≥ 2.5σ(I)).