An investigation into luminescent phenoxo-bridged heterobimetallic copper(II)–calcium(II)/strontium(II)-based bis(salamo)-like complexes.

Two luminescent hetero-trinuclear complexes [Cu₂Ca(L)(µ₂-NO₃)₂] (1) and [{Cu₂Sr(L)(µ₂-NO₃)(ƞ²-NO₃)}₂]·2EtOH·H₂O (2) have been prepared by a flexible bis(salamo)-based ligand (H₄L) with Cu(NO₃)·3H₂O and M(OAc)₂·nH₂O (M(II) = Sr, n = 2; Ca, n = 1), respectively. The structural characterizations were performed by physicochemical and spectroscopic methods. Two penta-coordinate Cu(II) atoms of complex 1 are sited at the N₂O₂-donor coordination environments of the (L)⁴⁻ moiety, while tetra- and penta-coordinate Cu(II) atoms in complex 2 are also located in the N₂O₂ cavities of the (L)⁴⁻ unit. Ca(II) and Sr(II) atoms are located in various O₈ and O₉ cavities, respectively. In the solid state, infinite 3D supra-molecular structures are formed in complexes 1 and 2 through the abundant intermolecular hydrogen bonds and π···π interactions. These interactions were quantitatively analyzed by Hirshfeld surface analyses. DFT calculations and fluorescence properties showed that complexes 1 and 2 have stable chemical properties and good luminescence properties. Two hetero-trinuclear complexes [Cu₂Ca(L)(µ₂-NO₃)₂] (1) and [{Cu₂Sr(L)(µ₂-NO₃)(ƞ²-NO₃)}2]·2EtOH·H₂O (2) have been synthesized and characterized structurally. Two penta-coordinate Cu(II) atoms in complex 1 are located in the N₂O₂ cavities of the (L)⁴⁻ unit, while tetra- and penta-coordinate Cu(II) atoms in complex 2 are also located in the N₂O₂ cavities of the (L)⁴⁻ unit. There are eight and nine oxygen donor atoms coordinating to the Ca(II) and Sr(II) atoms. Infinite 3D supra-molecular structures are formed in complexes 1 and 2 through the intermolecular hydrogen bonds and π···π stacking interactions. [ABSTRACT FROM AUTHOR]