INFINITE SQUARE-GRID [CD(CN)(2)](N) SHEETS LINKED TOGETHER BY EITHER PYRAZINE BRIDGES OR POLYMERIZABLE 1,4-BIS(4-PYRIDYL)BUTADIYNE BRIDGES ARRANGED IN AN UNUSUAL CRISSCROSS FASHION

The compounds Cd(CN)(2).pyz (py = 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 C-4 moieties are brought thereby into close proximity (closest C...C contact 3.36 Angstrom) 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.