Investigating poly-nuclear Zn(II) and Ni(II) complexes based on a formyl-appended single salamo-type ligand

Based on a salamo-type ligand H2L containing a bare formyl group, a di-nuclear salamo-Zn(II) complex [Zn2(L) Cl2] (1) was synthesized. With the occurrence of Claisen-Schmidt reaction catalyzed by triethylamine, the O4 coordination environment of the H2L ligand is destroyed, producing a new ligand H2L '. Which conflicts with the characteristics of Ni(II) atoms that are generally multi-coordinate, driving the occurrence of self-assembly re-action, and obtaining a tetra-nuclear salamo-Ni(II) complex [Ni4(L ')2(mu 2-Cl)2(mu 3-OMe)2(EtOH)2] (2). X-single crystal diffraction analyses showed that two Zn(II) atoms in the salamo-Zn(II) complex occupy the cavities of N2O2 and O4, respectively, while Ni1 and Ni1# atoms in the salamo-Ni(II) complex occupy the N2O2 cavities from two H2L ' ligands, there are many bridges (mu 2-Cl- & mu 3-OMe- aions) between Ni2 and Ni2# atoms. The UV-Vis titration experiments demonstrated the binding ratio of H2L to Zn(II) atoms is 1:2, while the binding ratio of the ligand H2L ' to Ni(II) atoms is also 1:2, the results are consistent with the X-ray single crystal structures. Through DFT calculation, the single-point energy of complexes 1 and 2 and the optimized structure of the ligand H2L were found that the softness of HOMO-LUMO gap of salamo-Zn(II) complex is small and not easy to deform, and the softness of salamo-Ni(II) complex is large and easy to deform, which is in agreement with the calculated results of intra-molecular interactions in IRI. The interaction of a large number of hydrogen bonds, C-H...pi, pi...pi, van der Waals forces and so on in salamo-Ni(II) complex makes it easy to deform. The fluorescence properties of H2L and the salamo-Zn(II) complex have also been studied.

Automated summary

A di-nuclear salamo-Zn(II) complex [Zn2(L) Cl2] (1) was synthesized using a salamo-type ligand H2L containing a bare formyl group. A new ligand H2L' was produced through the destruction of the O4 coordination environment of the H2L ligand in the presence of the Claisen-Schmidt reaction catalyzed by triethylamine. This led to the self-assembly reaction and the formation of a tetra-nuclear salamo-Ni(II) complex [Ni4(L ')2(mu 2-Cl)2(mu 3-OMe)2(EtOH)2] (2).