In:
European Journal of Inorganic Chemistry, Wiley, Vol. 2017, No. 42 ( 2017-11-16), p. 4909-4918
Abstract:
Two coordination polymers of assorted dimensionality (1D, 2D) have been prepared, namely [Zn 3 (L 2Th ) 4 (OH) 2 · 2(HL 2Th )] ∞ ( 1 ) and [Zn(L 5Th )(OAc)] ∞ ( 2 ), starting from Zn II salts and the isomeric forms of the organic linker p ‐(thiazolyl)benzoic acid: p ‐(2‐thiazolyl)benzoic acid (HL 2Th ) and p ‐(5‐thiazolyl)benzoic acid (HL 5Th ). The isomers have been prepared ad hoc, following straightforward Pd‐catalyzed C–C coupling reaction protocols. In 1 , the deprotonated ligand is coordinated through its carboxylate group only, with dangling thiazole groups. The –COO – units are bridging adjacent metal centers, thus creating a 1D chain. The Zn 3 cluster is made of one six‐coordinate (O h ) and two four‐coordinate (T d ) Zn II ions; triple‐bridging µ 3 ‐OH groups are balancing the overall positive charge. The structure of 2 is instead made of Zn 2 (carboxylate) 4 “paddle‐wheel” dimers as the constituting inorganic node. The octahedral metal coordination sphere includes two µ‐(κ‐COO) benzoate spacers, two µ‐(κ‐COO) acetate ions, the thiazole N atoms coming from adjacent building blocks, and a weak Zn ··· Zn axial interaction. The resulting final assembly is two‐dimensional (2D), where p ‐(5‐thiazolyl)benzoate adopts a genuine µ‐[κ(COO):κ(N)] bridging coordination mode. The luminescent properties of both polymers have been analyzed in the solid state; they feature ligand‐centered emissions at λ = 434 nm ( 1 ) and λ = 427 nm ( 2 ). These electronic transitions fall in the visible region, giving the samples a characteristic blue color under an ordinary UV lamp (excitation at λ = 254 nm). The theoretical analysis of the electronic features of the ligands and related molecular orbitals reveals that the observed transitions are mainly of π→π* nature, involving π orbitals delocalized on both aromatic cycles. A significant (reversible) blueshift of the emission maximum of ca. 60 nm, from the visible to the UV region, has been observed for 1 when suspended in water.
Type of Medium:
Online Resource
ISSN:
1434-1948
,
1099-0682
DOI:
10.1002/ejic.v2017.42
DOI:
10.1002/ejic.201700830
Language:
English
Publisher:
Wiley
Publication Date:
2017
detail.hit.zdb_id:
1475009-0
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