Structural Diversities of a Series of Cd(II) Coordination Complexes Based on a Flexible Tripodal N-donor Ligand

Huarui Wang,Jianhua Qin

doi:10.3390/cryst12010053

Abstract

Three Cd(II) coordination complexes with unique structures and topologies, namely, {[Cd(tttmb)(Hbtc)]·5H2O}n (1), {[Cd(tttmb)(m-phda)(H2O)]·2H2O}n (2), and {[Cd(tttmb)(o-cpla)]·(CH3CN)·(H2O)1.5}n (3), have been successfully synthesized under hydro(solvo)thermally condition based on a flexible tripodal N-contained ligand 1,3,5-tris(1,2,4-triazol-1-ylmethyl)-2,4,6-trimethylbenzene (tttmb) and aromatic polycarboxylate acids (H3btc = 1,2,4-benzenetricarboxylic acid, m-H2phda = 1,3-phenylenediacetic acid and o-H2cpla = Homophthalic acid). Complexes 1–3 were characterized by elemental analysis, IR spectroscopy, X-ray single-crystal diffraction and thermogravimetric analyses. 1 crystallize in the orthorhombic chiral space group P212121 and feature 3D coordination networks. 2 reveals a 2D ladder-like structure with (4,4) topology containing alternating Cd(II)/m-phda2− left- and right-handed helical motifs. 3 exhibits a 3D net with (63)(66)(7·82) topology. The structural and dimensional diversity of these complexes not only indicates that the flexible ligand tttmb exhibits strong coordination ability and diverse coordination modes, but also shows that aromatic polycarboxylates play important roles in constructing the frameworks of complexes. Moreover, the different photoluminescence behaviors of 1–3 have been studied in the solid state.

Highlights

In order to obtain unique MOFs with interesting properties, many flexible ligands have been widely employed as linkers of metal ions, flexible N-donor bridging ligands [1,2,3,4,5]
Triazole containing ligands usually have strong coordination ability to transition metal ion centers For example, as multifunctional organic linkers, 1,2,4-triazole and its derivatives can possess a combination of the advantages of the coordination geometries of both pyrazole and imidazole, and provide more potential coordination sites [11,12]
We have successfully synthesized three new Cd(II) complexes based on tttmb and different aromatic polycarboxylate ligands under hydro(solvo)thermal conditions

Summary

Introduction

In order to obtain unique MOFs with interesting properties, many flexible ligands have been widely employed as linkers of metal ions, flexible N-donor bridging ligands [1,2,3,4,5]. Triazole containing ligands usually have strong coordination ability to transition metal ion centers For example, as multifunctional organic linkers, 1,2,4-triazole and its derivatives can possess a combination of the advantages of the coordination geometries of both pyrazole and imidazole, and provide more potential coordination sites [11,12]. 1,2,4-triazole-containing ligands can often be influenced by exterior factors; specific structures and functions can be used to coordinate different metal ions. Polycarboxylate organic ligands, which have good coordination ability and various coordination modes, have proven to be excellent structural contributors [13,14,15]. The coordination complexes based on the mixed 1,2,4-triazole-containing and polycarboxylate-based ligands were explored with complicated coordination environments. A series of 1,2,4-triazole-containing ligands with distinct orientation and flexibility were reported, as 1,4-bis(1,2,4-triazol-1-ylmethyl)-benzene (bbtz), 4,40 -bis(1,2,4-triazol-1ylmethyl)biphenyl (btmb), 1,4-bis(1,2,4-triazol-1-yl)butane (btb), 1,3,5-tris(1,2,4-triazol-1-

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