1 Acta Chim. Slov. 2021, 68, – Yolcu et al.: A Novel Cd(II) Isophthalate Complex ... 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 DOI: 10.17344/acsi.2020.6620 Scientific paper A Novel Cd(II) Isophthalate Complex with Triethanolamine: Crystal Structure, Fluorescence and Antimicrobial Activity Zuhal Yolcu, 1,* Sinem Yurtcan 2 and Meryem Çıtlakoğlu 1 1 Department of Chemistry, Faculty of Art and Science, Giresun University, Giresun, Turkey 2 Giresun University Central Research Laboratory Application and Research Center * Corresponding author: E-mail: zuhal.yolcu@giresun.edu.tr Received: 12-22-2020 Abstract A mixed ligand Cd(II) complex [Cd(IsoPht)(TEA)H 2 O]·3H 2 O was synthesized for the first time by using isophthalic acid (H 2 IsoPht) and tetradentate triethanolamine (TEA) and characterized by X-ray single-crystal diffraction, FT-IR, and thermogravimetric analysis (TGA). is novel complex crystallizes in the triclinic system with P-1 space group and distorted monocapped trigonal prismatic geometry. e Cd(II) has seven coordinates with bidentate IsoPht, a TEA in the tetradentate mode, and an aqua ligand. e fluorescence properties of the Cd(II) complex and TEA ligand were in- vestigated at room temperature. e present Cd(II) complex was also tested for its antimicrobial activity by in vitro agar diffusion method against some Gram-positive and Gram-negative bacteria and a fungus. Keywords: Isophthalic acid; triethanolamine; Cd(II) complex; X-ray single crystal; antimicrobial activity 1. Introduction Triethanolamine (TEA) is a potential ligand that can interact with metal ions to form supramolecular complex- es with different structures, and many coordination com- pounds containing TEA ligands have been reported for the last two decades. 1–6 TEA is also used as a pH regulator in cosmetology, as a corrosion inhibitor in metal-cutting flu- ids, as a curing agent for epoxy and rubber polymers, in adhesives, antistatic agents, or as a pharmaceutical inter- mediate. 7–9 TEA generally acts as the tri- or tetradentate ligand, but some metal complexes with mono- or bidentate TEA coordination modes are also known. 10,11 Metal com- plexes containing TEA ligand can be (neutral or cationic) mono-, bi- and polynuclear structures. 12,13 Some mononu- clear mixed ligand complexes were reported for Ni(II) with TEA and orotic acid, 14 Cu(II) with TEA and malonic acid, 15 Zn(II) and Cd(II) with TEA and p-nitrobenzoic acid, 16 Zn(II) with TEA and aqua ligand, 17 Cu(II) with TEA, aqua and 1H-imidazole ligands, 18 aqua ligand. 19 Based on the collaborative use of TEA and phthalic acid, mononuclear complexes for Ni(II), 20 Zn(II), 21 Cd(II), 22 and coordination polymer for Cd(II) 23 were also reported. Although TEA has no specific physiological effects except for its low antibacterial activity, as an auxiliary ligand TEA may increase the physiological effect of bioactive substanc- es in mixed ligand metal complexes. 8,9,24 ere are prelim- inary pharmacological studies demonstrating that the transition metal complexes of TEA protect animals from ethanol and carbon monoxide poisoning and have im- mune-modulating and antiproliferative properties. 25-27 Also, the mixed ligand zinc complex containing TEA has been reported to have anti-angiogenic and anti-atherogen- ic effects. 28 Coordination compounds may combine a metal ion, a biocompatible ligand, and some auxiliary ligands in the same molecule to form mixed-ligand coordination types to achieve the desired properties. 29,30 Apart from the TEA ligand, isophthalic acid (H 2 IsoPht) has been selected as a good candidate for this purpose. Dicarboxylic acids have important advantages in design of coordination com- pounds compared with other organic ligands. Isophthalic acid has two carboxyl groups that can lose one or two pro- tons to form various coordination modes, act as a hydro- gen bond acceptor and donor. So it is a versatile and vari- able ligand that can bind metal ions in different directions. 31–38 e synthesis of coordination compounds containing O and/or N-donor ligands are very significant