Construction of 2D interwoven and 3D interpenetrated metal–organic frameworks of Zn(ii) by varying N,N′-donor spacers

Abstract

Four new metal–organic frameworks (MOFs) of Zn(II) ions, [Zn₂(muco)₂(azopy)₂]·3DMF·2H₂O (1), [Zn(muco)(bpee)]·4H₂O (2), [Zn(muco)(3bpdh)] (3), and [Zn₄(muco)₄(4bpdh)₄]·4bpdh·2H₂O (4) (where, muco = trans,trans-muconate dianion, azopy = 4,4′-bisazobipyridine, bpee = 1,2-bis(4-pyridyl)ethylene, 3bpdh = 2,5-bis(3-pyridyl)-3,4-diaza-2,4-hexadiene, and 4bpdh = 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene) have been synthesized using mixed ligand systems and characterized structurally by single-crystal X-ray diffraction. Compound 1 has a 2D network with 2-fold interwoven, (4,4)-connected, {4⁴·6²}-sql net topology. Compounds 2 and 3 have 3D diamondoid (dia) structures with interesting 5-fold and 3-fold interpenetrated nets, respectively, whereas, compound 4 has a 3D cubic (pcu, α-Po) structure with 2-fold interpenetrating, 6-connected, {4¹²·6³} net topology. Topological analyses of 2 and 3 reveal 4-connected nets with 6⁶ topology. In spite of the interweaving/interpenetration, compounds 1 and 2 possess rectangular channels with dimensions of 3.9 × 4.5 Ų and 4.3 × 7.0 Ų, respectively. Photoluminescence studies showed the emissions of 1–4 and the thermal stabilities of the compounds were also examined.