Infinite square-grid [Cd(CN)2]n sheets linked together by either pyrazine bridges or polymerisable 1,4-bis(4-pyridyl)butadiyne bridges arranged in an unusual criss-cross fashion

Abstract

The compounds Cd(CN)₂·pyz (pyz = pyrazine) and Cd(CN)₂·bpb [bpb = 1,4-bis(4-pyridyl)butadiyne] contain square-grid [Cd(CN)₂]_n sheets linked together by either pyrazine bridges or bpb bridges which criss-cross in an unusual fashion producing face-to-face stacks of pyrazine rings and collections of bpb units in which every one is sandwiched between six others, three on each side; butadiyne C₄ moieties are brought thereby into close proximity (closest C ⋯ C contact 3.36 Å) and the initially colourless Cd(CN)₂·bpb crystals acquire a deep blue-purple colour on exposure to light indicating diacetylene polymerisation within the crystal.