Two Zn(II) complexes of trans-4-styrylpyridine ligands undergo [2+2] cycloaddition reaction forming Zn(II) complex dimers in a single-crystal to single-crystal (SCSC) manner which were thermally reversible. The dimers are presumed to be the stable intermediates in the formation of 1D coordination polymers upon prolonged exposure to UV light.
![Graphical abstract: Thermally reversible single-crystal to single-crystal transformation of mononuclear to dinuclear Zn(ii) complexes by [2+2] cycloaddition reaction](http://hg.y866.cn/compound/lib/scimg/usr/1/C3CC45706K.jpg)
