Highly selective detection of Hg2+ and MeHgI by di-pyridin-2-yl-[4-(2-pyridin-4-yl-vinyl)-phenyl]-amine and its zinc coordination polymer

Solvothermal reaction of Zn(NO3)(2)center dot 6H(2)O with di-pyridin-2-yl-[4-(2-pyridin-4-yl-vinyl)-phenyl]-amine (ppvppa) and 1,4-naphthalenedicarboxylic acid (1,4-H2NDC) in H2O and MeCN at 150 degrees C yielded a two-dimensional (2D) coordination Zn(II) polymer [Zn(ppvppa)(1,4-NDC)](n) (1). Compound 1 was characterized by elemental analysis, IR spectroscopy, powder X-ray diffraction, single-crystal X-ray diffraction and thermogravimetric analysis. Compound 1 consists of dimeric [Zn-2(ppvppa)(2)] units linked by 1,4-NDC bridges to generate a 2D honeycomb network. Either compound 1 or ppvppa alone can detect Hg2+ or MeHgI selectively and with good sensitivity. Upon addition of Hg2+ ions to a MeCN solution of ppvppa, marked changes in the UV-vis and fluorescence spectra are observed, associated with colour changes, which are easily identified by the naked eye. The pyridinyl rings of ppvppa are coordinated to the Hg2+ ion. This motif in the presence of NO3- ions forms a binuclear complex [Hg-2(ppvppa)(2)(NO3)(4)] (2), which has been characterized as the solvate [Hg-2(ppvppa)(2)(NO3)(4)]center dot H2O center dot 4MeCN (2H(2)O center dot 4MeCN) by single-crystal X-ray diffraction studies. In aqueous solution, compound 1 emits pale orange light at ambient temperature and the addition of Hg2+ or MeHgI induces an change of fluorescence color from pale orange to blue. Compound 1 is a promising candidate as a sensitive naked-eye indicator for Hg2+ or MeHgI in water under a UV lamp.