pubmed-article:19957919 | pubmed:abstractText | A triple-stranded ladder coordination polymer, [Pb(3)(bpe)(3)(O(2)CCF(3))(4)(O(2)CCH(3))(2)] [bpe = trans-1,2-bis(4-pyridyl)ethene] undergoes a photochemical [2 + 2] cycloaddition reaction in the solid state to furnish 100% rctt-tetrakis(4-pyridyl)cyclobutane (rctt-tpcb) in two steps via cooperative molecular movements of the partially dimerized products formed initially. | lld:pubmed |