Document Detail

Thermal Cleavage of Cyclobutane Rings in Photodimerized Coordination-Polymeric Sheets.
MedLine Citation:
PMID:  22544442     Owner:  NLM     Status:  Publisher    
Three coordination polymers, [Cd(2) (pvba)(2) (tbdc)(dmf)(2) ] (1), [Co(2) (pvba)(2) (tbdc)(dmf)(2) (H(2) O)(2) ] (2), and [Ni(2) (pvba)(2) (tbdc)(dmf)(2) (H(2) O)(2) ] (3) (H(2) tbdc=2,3,5,6-tetrabromobenzenedicarboxylic acid, Hpvba=trans-2-(4'-pyridyl)vinylbenzoic acid), were synthesized by solvothermal methods. The solid-state structures of compounds 1 and 2 were determined by X-ray crystallography. In compounds 1 and 2, the bimetallic cores acted as secondary building units that connected the tbdc ligands in one direction and a pair of pvba ligands, which were aligned in a head-to-tail parallel manner, in the orthogonal direction to form sheet structures. The CC bonds in these pvba ligand pairs in all three compounds were well-aligned to undergo quantitative [2+2] cycloaddition reactions in the solid state under UV irradiation, thereby yielding their cyclobutane derivatives. This photochemical reaction appeared to facilitate structural transformations from one 2D structure into another in the solid state. The photoreactive Co(II) - and Ni(II) coordination polymers exhibited a reversible dehydration-rehydration reaction that was accompanied by color changes from pink to purple and green to yellow, respectively, owing to a change in coordination number from six to five. Magnetic studies showed that compound 2 was an antiferromagnet, which displayed a field-dependent transition with a critical field (H(c) ) of 40 kOe at 2 K; the antiferromagnetic interaction between the Co(2) units was strengthened and weakened by dehydration and UV irradiation, respectively. The cyclobutane ligand in the photodimerized products was cleaved on heating to yield a mixture of trans- and cis-isomers of pvba, as monitored by (1) H NMR spectroscopy. The Cd(II) coordination polymer underwent quantitative cleavage of the cyclobutane ring whilst the other two underwent partial cleavage.
Anjana Chanthapally; Goutam Kumar Kole; Kang Qian; Geok Kheng Tan; Song Gao; Jagadese J Vittal
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-4-27
Journal Detail:
Title:  Chemistry (Weinheim an der Bergstrasse, Germany)     Volume:  -     ISSN:  1521-3765     ISO Abbreviation:  -     Publication Date:  2012 Apr 
Date Detail:
Created Date:  2012-4-30     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9513783     Medline TA:  Chemistry     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Department of Chemistry, National University of Singapore, 3 Science Drive 3, 117543 (Singapore), Fax: (+65) 6779-1691.
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