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Solid‐State Photochemical [2+2] Cycloaddition in a Hydrogen‐Bonded Metal Complex Containing Several Parallel and Crisscross CC bonds
Author(s) -
Peedikakkal Abdul Malik Puthan,
Vittal Jagadese J.
Publication year - 2008
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200701494
Subject(s) - cyclobutane , cycloaddition , chemistry , hydrogen bond , solid state , photochemistry , metal , crystallography , molecule , ring (chemistry) , catalysis , organic chemistry
One‐dimensional hydrogen‐bonded complex [Zn(bpe) 2 (H 2 O) 4 ](NO 3 ) 2 ⋅8/3 H 2 O⋅2/3 bpe ( 1 , bpe=4,4′‐bipyridylethylene) containing coordination complex cations [Zn(bpe) 2 (H 2 O) 4 ] 2+ with parallel and crisscross double bonds undergoes photochemical [2+2] cycloaddition in the solid state and produces tetrakis(4‐pyridyl)cyclobutane (tpcb) in up to 100 % yield with rctt ‐tpcb ( 2 a ) as major and rtct ‐tpcb ( 2 b ) as minor product. The bpe ligands with crisscross conformation of CC bonds appear to undergo pedal‐like motion prior to photodimerization. Grinding single crystals to powder accelerates the pedal motion of crisscrossed olefins in the bpe ligands to parallel alignment and provides the rctt‐ cyclobutane stereoisomer 2 a quantitatively. In addition, 100 % photodimerization of ground 1 indicates that the free bpe ligands, which are remote from each other in a pool of water, and NO 3 − ions moved toward each other to give a mixture of rctt ‐ and rtct ‐tpcb isomers.