Synthesis, structures and DFT calculations of 2-(4,6-dimethyl pyrimidyl)selenolate complexes of Cu(i), Ag(i) and Au(i) and their conversion into metal selenide nanocrystals

Abstract

The complexes [M{SeC₄H(Me-4,6)₂N₂}]₆ (M = Cu (1), Ag (2)) and [Au{SeC₄H(Me-4,6)₂N₂}(PEt₃)] (3) have been prepared and characterized by elemental analyses, UV-vis, NMR (¹H, ¹³C, ⁷⁷Se) spectroscopy and single crystal X-ray diffraction. The crystal structures of [Cu{SeC₄H(Me-4,6)₂N₂}]₆·H₂O (1·H₂O), [Ag{SeC₄H(Me-4,6)₂N₂}]₆·6MeOH·H₂O (2·6MeOH·H₂O) and [Au{SeC₄H(Me-4,6)₂N₂}(PEt₃)] (3) revealed that their metal centers acquire distorted square-pyramidal, trigonal and linear geometries, respectively. DFT calculations have been carried out to rationalize nuclearity in copper(I) chalcogenolate complexes. The calculations suggest that there is hardly any energy difference between the tetrameric and hexameric forms. Thermal behavior of [Cu{SeC₄H(Me-4,6)₂N₂}]₆ was studied by thermogravimetric analysis. Thermolysis of [M{SeC₄H(Me-4,6)₂N₂}]₆ (M = Cu, Ag) in 1-dodecanethiol (DDT) at 150 °C gave a cubic phase of Cu₇Se₄ and an orthorhombic phase of Ag₂Se, respectively. Copper selenide (Cu₇Se₄) thin films were deposited on glass and silicon substrates by using [Cu{SeC₄H(Me-4,6)₂N₂}]₆ at 400 °C by AACVD.