Several symmetrical and unsymmetrical bis-selenacyclophanes were prepared and characterized by multinuclear (1H, 13C {1H} and 77Se {1H}) NMR. The symmetrical cyclophanes of phenyl, furyl, pyridyl and thiophenyl appear to exist in predominantly syn conformation in solution at room temperature. VT-1H NMR of some cyclophanes indicate that the equilibrium between the syn conformers which differ in the disposition of the ...