Abstract
A tetracoordinated [Hg 2(L 1)(SCN) 4] ( 1) [L 1 = N,N′-(bis-(pyridin-2-yl)benzylidene)-1,2-ethanediamine] and two pentacoordinated [Hg 2(L 2)(X) 4] [L 2 = N-((1-pyridin-2-yl)formylidene)-N′-[2-(4-{2-[((1-pyridin-2-yl)formylidene) amino]ethyl}piperazin-1-yl)ethyl]amine; X = N 3 - , ( 2) and X = NCS −, ( 3)] dinuclear mercury(II) compounds have been prepared and characterized using microanalytical, spectroscopic, thermal and X-ray crystallographic results. Structural analyses reveal bis(bidentate) congregation behaviour of classical tetradentate L 1 and bis(tridentate) character of L 2 encapsulating two metal centers. Each mercury(II) center in 1 is in a distorted tetrahedral coordination environment with HgN 2S 2 chromophore. Hg(1) is attached with two N atoms of L 1 and two S atoms of two terminal thiocyanates whereas neighbouring Hg(1) is ligated to the other two N donor set of the same Schiff base completing its bis(bidentate) mode and two S atoms of thiocyanates. In 2 and 3 each mercury(II) center adopts a distorted square pyramidal geometry with MN 5 (in 2) and MN 3S 2 (in 3) chromophores and two metal(II) centers are encapsulated by bis(tridentate) congregation behaviour of L 2 through donation of three N donor set to each metal and the fourth and fifth positions are occupied by two N atoms of terminal azides in 2 and two S atoms of terminal thiocyanates in 3. In solid-state, dinuclear units of 1 pack through cooperative C–H⋯N and C–H⋯S hydrogen bonds and C–H⋯π interactions giving rise to a 3D network. Individual dinuclear units of 2 and 3 self-assemble through cooperative C–H⋯N hydrogen bondings and C–H⋯π interactions affording 3D network structure and 2D continuum, respectively. In DMF solutions at room temperature all the complexes display high-energy intraligand 1(π–π∗) fluorescence.
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