Four 2D metal–organic networks incorporating Cd-cluster SUBs: hydrothermal synthesis, structures and photoluminescent properties

TLDR: In this paper, the second ligands of bpydo, bpe, bpp and bix (bpydo = 4,4′-bipyridine-N,N′-dioxide; bpe = 1,2-bis-(4-pyridyl)ethane; bpp = 1.4-bis(imidazol-1-yl-methyl)benzene); bix = bix, b.

Abstract: Hydro(solvo)thermal reactions between 1,1′-biphenyl-2,2′,3,3′-tetracarboxyl acid (H4bptc) and Cd(NO3)2·4H2O at the presence of the ‘second’ ligands of bpydo, bpe, bpp and bix (bpydo = 4,4′-bipyridine-N,N′-dioxide; bpe = 1,2-bis-(4-pyridyl)ethane; bpp = 1,3-Bis-(4-pyridyl)propane; bix = 1,4-bis(imidazol-1-yl-methyl)benzene) yield four new 2D metal–organic coordination polymers [Cd9(bptc)4(μ3-OH)2(H2O)14]·(bpydo)·2H2O (2), [Cd2(bptc)(bpe)(H2O)2]·H2O (3), [Cd4(bptc)(Hbptc)(bpp)(μ3-OH)(H2O)4] (4), [Cd2(bptc)(bix)(H2O)] (5). Compound 2 presents a 2D grid structure with heptanuclear cadmium cluster and two kinds of discrete Cd atoms secondary building units (SUBs), 3 has a 2D structure with the novel Schlafli symbol of (4.62)(43.63)(44.610.8), 4 gives a 2D grid structure with a pentanuclear cadmium cluster, binuclear cadmium cluster and discrete Cd atom SUBs, and 5 has a 2D distorted CdI2-type topology structure with the Schlafli symbol of (43)2(46.66.83). The novel achiral crown-ether-like cycles in 2, 4 and 5 are found and occupied by the single Cd atom or binuclear cadmium cluster. All compounds give strong luminescent emission and have potential application as optical materials.