Second Ligand-Directed Assembly of Photoluminescent Zn(II) Coordination Frameworks

Abstract

Three new coordination polymers, {[Zn(H2Bpz)(Tph)]·1/2(H2Bpz)} n (1), [Zn 2 (H2Bpz)(Bpz)(Iph)] n (2), and {[Zn 2 (H2Bpz)(HBtc) 2 (H2O) 2 ]·7/6(H2O)} n (3) (H2Bpz = 3,3‘,5,5‘-tetramethyl-4,4‘-bipyrazole; H2Tph = terephthalic acid; H2Iph = isophthalic acid; H3Btc = benzene-1,3,5-tricarboxylic acid), have been isolated from parallel hydrothermal reactions of ZnSO4 and H2Bpz with H2Tph, H2Iph, and H3Btc, respectively. These crystalline solids have been structurally defined, of which 1 was revealed to construct in a 3D architecture with porosity. Interestingly, because of its large porosity, 1 allows the concurrent 2-fold interpenetration and inclusion of free H2Bpz as guest molecule. In contrast to 1, polymer 2 structures in a 2D framework of note for containing both neutral and deprotonated H2Bpz as μ2-and μ4-bridging linkers, respectively. This case demonstrates a rare usage of H2Bpz as ligand in the construction of MOFs. The partial deprotonation of H2Bpz may be a consequence of less acidity of H2Iph than H2Tph, by which the influence of a second ligand on the reactivity of the main ligand is reified. Likewise, 3 is also assembled in a 2D framework, containing H2Bpz and monoacid HBtc2- as ligands, which indicates the stronger acidity of H3Btc. Moreover, to probe the effect of substitution of second ligands, we have investigated the luminescence of 1−3 in the solid state at room temperature, revealing that the polymers are photoluminescent and their emissions are varied with the alteration of second ligands.

Synthesis, crystal structure, thermal stability, and photoluminescence of a 3-D silver(I) network with twofold interpenetrated dia-f topology

“…The free bpz display photoluminescence with emission maxima at 331 nm. These peaks originate from the π*→n or π*→π transitions [62,63]. Complex 1 exhibits photoluminescence with an emission maximum at 470 nm, upon excitation at 365 nm at room temperature.…”

Synthesis and applications of bipyrazole systems

“…[166][167][168] Poly(5,5'-bipyrazole-3,3'-diyl) derivatives 352 were synthesized from 3,3'-dichloro-5,5'-bipyrazoles 347 through dehalogenative polycondensation using a mixture of Ni(cod) 2 and 2,2´-bipyridine in DMF at 60 °C (Scheme 99). The obtained polymers were characterized by their high thermal stability and electrochemical activity.…”

Synthesis, Structure and Luminescence of Two Coordination Polymers Based on 1,4‐Benzenedicarboxylate and 2‐(3‐Pyridyl)benzimidazole Ligands

“…It was reported that H 2 Bdc acid and {[Zn(H 2 Bpz)(Bdc)]-(H 2 Bpz) 1/2 } n complex exhibited emissions at 382, 470 nm, respectively. 18 However, the luminescence of 3-PyHBIm is unclear, although isomer 4-PyHBIm shows an emission band centered at 492 nm with 370 nm light excitation. 19 We determined the emission bands of 3-PyHBIm under 370, 379 and 383 nm light excitations, which shows a similar emission with a band maximum at 574 nm.…”

“…The energy of the luminescence strongly suggests that the emissions of 1 and 2 are Bdc 2-ligand-centered transitions rather than LMCT, especially since Cd(II) and Zn(II) are not oxidizable or reducible ions. 18 …”