A synthetic approach to heteroleptic Zn2Ln2 complexes featuring photoluminescence, antibacterial and anticancer properties

Abstract

Through addition reactions between [Zn(phen)X₂] (phen = 1,10-phenanthroline, X = CF₃SO₃⁻ (Otf), CF₃COO⁻ (1)) and lanthanide carboxylates in acetonitrile, heterometallic molecular [Zn₂Gd₂(phen)₂(μ-fur)₈(OOCCF₃)₂(H₂O)₂] (2) and ionic [Zn₂Eu₂(phen)₂(μ-piv)₈(H₂O)₄](Otf)₂ (3) (fur = furoate-anion, piv = trimethylacetate-anion) complexes were synthesized and characterized. According to the X-ray data, 2 and 3 are tetranuclear complexes in which two lanthanide and two zinc atoms are bound by eight bridging carboxylate anions and contain two terminal chelated 1,10-phenanthroline. In crystals 1–3, the phen fragments of neighboring complexes participate in π⋯π interactions forming infinite chains. The photophysical properties of 2 and 3 were studied, and the relaxation times of the excited states, and the quantum yield for 3 were determined. The study of the biological properties of all the complexes showed high antibacterial activity against non-pathogenic M. smegmatis (MIC = 10 nmol per disk), and a selective antiproliferative effect in the test line of ovarian cancer SKOV3 (IC₅₀ for 2 is 4 μM and the selectivity index is 2.6).