Solvent-driven self-assembly of two novel di- and tetra-nuclear Cu(II) bis(salamo)-based complexes

Two novel di-and tetra-nuclear Cu(II) complexes, [Cu2(HL)Cl2(MeOH)] center dot MeOH (1) and [Cu4(HL)2Cl2(mu 2- Cl)2] center dot 4EtOH center dot H2O (2) (where H3L = bis(salamo)-based ligand) have been synthesized, and structurally char-acterized by elemental analysis, infrared and electronic absorption spectroscopy. The molecular structures of complexes 1 and 2 were defined by using single crystal X-ray diffraction experiment. The structural re-sults indicated that complexes 1 and 2 have a close comparable [Cu2(HL)Cl2] unit in the unit cell where the ligand acts as a two-compartmental species chelating the metal ions Cu1 and Cu2. However, in com-plex 2 , the [Cu2(HL)Cl2] complexes are paired in a centrosymmetric fashion to form a tetra-nuclear ar-rangement, connected by mu 2-bridging chlorides. The observed different nuclearity is likely induced by the different solvent molecules used in the syntheses, methanol and ethanol in complexes 1 and 2 , respec-tively. A methanol molecule participates in coordination of complex 1 , while ethanol species in complex 2 is rather distant from one of the Cu(II) ions ( ca 2.82 A). The molecular frontier orbitals HOMO and LUMO of the complexes were analyzed by DFT calculations, and the results showed that the energy gaps of complexes 1 and 2 are particularly small compared to H3L, which may be caused by the combination of the orbitals of the central atoms and the donor atoms. The reaction sites of the ligand H3L with the metal Cu(II) were analyzed by ESP studies, and the results showed that the experiments were in agree-ment with the theory. Finally, Hirshfeld surfaces analyses were performed to quantitatively show various weak interactions of complexes 1 and 2 . (c) 2022 Elsevier B.V. All rights reserved.

Automated summary

Two novel di- and tetra-nuclear Cu(II) complexes were synthesized and structurally characterized. The molecular structures were determined by single crystal X-ray diffraction, revealing the influence of different solvent molecules on the nuclearity of the complexes. DFT calculations and ESP studies were conducted to analyze the molecular orbitals and coordination sites, and Hirshfeld surfaces were used to quantify the weak interactions in the complexes.