Mixed-ligand coordination polymers from 1,2-bis(1,2,4-triazol-4-yl)ethane and benzene-1,3,5-tricarboxylate: Trinuclear nickel or zinc secondary building units for three-dimensional networks with crystal-to-crystal transformation upon dehydration

Abstract

The hydrothermal reaction of M(NO3)2.6H2O (M = Ni and Zn) with benzene-1,3,5-tricarboxylic acid (H3btc) and 1,2-bis(1,2,4-triazol-4-yl)ethane (btre) produced the mixed-ligand coordination polymers (MOFs) 3 infinity{[Ni3(mu3-btc)2(mu(4)-btre)2(mu-H2O)2]. approximately 22H2O} (1) and 3 infinity{[Zn3(mu4-btc)2(mu4-btre)(H2O)2].2H2O} (3). The compounds, characterized by single-crystal X-ray diffraction, X-ray powder diffraction and thermoanalysis feature trinuclear secondary building units (SBU) within the three-dimensional frameworks. The trinuclear nickel unit in 1 exhibits an intra-trimer together with some weak inter-trimer antiferromagnetic coupling with J = -13.88(8) cm(-1) from the magnetic susceptibility measurement between 1.9-300 K. The zinc coordination polymer 3 shows a strong fluorescence at 423 nm upon excitation at 323 nm (not seen in the free btre ligand). Compound 3 is thermally robust until 200 degrees C (ambient pressure) where loss of the water molecules starts. Careful control of the dehydration procedure (freeze-drying) for 1 and (heating to 280 degrees C) for allowed for a solid-state reaction with single-crystal-to-single-crystal structural transformations in obtaining the largely dehydrated products 3 infinity{[Ni3(mu2-btc)2(mu4-btre)2(mu-H2O)2(H2O)2].4H2O} (2) and 3 infinity{[Zn3(mu6-btc)2(mu4-btre)2]. approximately 0.67H2O} (4), respectively. In the transformation from 1 to 2 the unit cell volume is reduced to about 60%. The transition from 3 to 4 involves breakage and formation of new Zn-O bonds.

A Cadmium Anionic 1-D Coordination Polymer {[Cd(H2O)6][Cd2(atr)2(μ2-btc)2(H2O)4] 2H2O}n within a 3-D Supramolecular Charge-Assisted Hydrogen-Bonded and π-Stacking Network

“…The combination of neutral nitrogen donor ligands with anionic carboxylate ligands are frequent choices for the synthesis of mixed-ligand networks [22]. The linker 1,2-bis(1,2,4-triazol-4-yl)ethane (abbreviated as btre, Scheme 1) has recently been intensely studied in mixed-linker MOFs [19][20][21][22][23][24] and single-linker networks [25]. Herein, we report an attempt to construct a mixed-linker network with the 4,4 1 -bis(1,2,4-triazol-4-yl) (btr) ligand which was not hydrothermally stable under the synthesis conditions of 125˝C in water, so that the hydrolysis product 4-amino-1,2,4-triazole (atr) was incorporated instead (Scheme 1).…”

“…Coordination polymers based on mixed-linkers allow for a fine-tuning of MOF properties and can show additional characteristics such as crystal-to-crystal transformations [19], short and long-range magnetic ordering [20], luminescence [21], etc. [22].…”

A Novel Twofold Interpenetrating 2D (3,5)-Connected Cd(II) Coordination Framework with (52.6)(55.64.7) Topology

“…Such fluorescent enhancement from the free ligand to the coordination polymer may be a result of (a) coordination with d 10 metals, which strengthen the rigidity of the organic ligand, (b) deprotonation of ligand and (c) p-p stacking interactions among aromatic rings from interpenetrating fragments [16,[66][67][68][69][70]. The fluorescent behavior of 1 is due mainly to a metal-perturbed intraligand (p-p*) emission state, which is similar to other coordination polymers of d 10 metal ions and nitrogen-or oxygen-containing bridging ligands [71][72][73][74][75][76].…”

Synthesis and crystal structure of 1D Cd-amine coordination polymer and its luminescent properties

“…The coordination environment of the Cd(II) center is best described by a slightly distorted octahedron [CdN 6 ]. In compound 1, the six nitrogen atoms are in the same coordination environment, therefore, the Cd-N distances are both 0.2417 nm, which are within the normal distances of those observed in Cd(II)-coordination polymers [26][27][28][29][30] . The bond angles around Cd(II) are in a range of 83.67°[N1-Cd-N1D(N1F)]-96.33°[N1-Cd-N1C(N1E)], and the dihedral angle of the benzene rings is 60°.…”