Abstract
Three 2,1,3-benzothiadiazole-based ligands decorated with two pyridyl groups, 4,7-di(2-pyridyl)-2,1,3-benzothiadiazol (2-PyBTD), 4,7-di(3-pyridyl)-2,1,3-benzothiadiazol (3-PyBTD) and 4,7-di(4-pyridyl)-2,1,3 benzothiadiazol (4-PyBTD), generate ZnII and AgI complexes with a rich structural variety: [Zn(hfac)2(2-PyBTD)] 1, [Zn2(hfac)4(2-PyBTD)] 2, [Ag(CF3SO3)(2-PyBTD)]23, [Ag(2-PyBTD)]2(SbF6)24, [Ag2(NO3)2(2-PyBTD)(CH3CN)] 5, [Zn(hfac)2(3-PyBTD)] 6, [Zn(hfac)2(4-PyBTD)] 7, [ZnCl2(4-PyBTD)2] 8 and [ZnCl2(4-PyBTD)] 9 (hfac = hexafluoroacetylacetonato). The nature of the resulting complexes (discrete species or coordination polymers) is influenced by the relative position of the pyridyl nitrogen atoms, the nature of the starting metal precursors, as well as by the synthetic conditions. Compounds 1 and 8 are mononuclear and 2, 3 and 4 are binuclear species. Compounds 6, 7 and 9 are 1D coordination polymers, while compound 5 is a 2D coordination polymer, the metal ions being bridged by 2-PyBTD and nitrato ligands. The solid-state architectures are sustained by intermolecular π–π stacking interactions established between the pyridyl group and the benzene ring from the benzothiadiazol moiety. Compounds 1, 2, 7–9 show luminescence in the visible range. Density Functional Theory (DFT) and Time Dependent Density Functional Theory (TD-DFT) calculations have been performed on the ZnII complexes 1 and 2 in order to disclose the nature of the electronic transitions and to have an insight on the modulation of the photophysical properties upon complexation.
Highlights
Introduction of coordinating groups on the benzene ring affords neutral or anionic ligands allowing the formation of luminescent discrete complexes or coordination polymers in which the thiadiazole nitrogen atoms can take part, or not, to the coordination of metal centers [24]
The scope of the study has been extended towards the use of ZnCl2, as it provides tetrahedral ZnCl2 L2 complexes with pyridine based ligands [41], at the difference with the {Zn(hfac)2 } fragment which favors the formation of octahedral Zn(hfac)2 L2 complexes
In the following discussion we describe in detail the crystal structures of the complexes obtained with each of the three ligands, together with the photophysical properties of the zinc(II) complexes with 2-PyBTD and 4-PyBTD
Summary
The 2,1,3-benzothiadiazole (BTD) unit is an electron acceptor fluorophore [1], which has been extensively used in the structure of derivatives and materials for various applications such as organic field-effect transistors [2,3,4], light emitting diodes [5,6], photovoltaics [7,8,9,10,11], redox switchable donor-acceptor systems [12,13], fluorescent probes [14,15]. Introduction of coordinating groups on the benzene ring affords neutral or anionic ligands allowing the formation of luminescent discrete complexes or coordination polymers in which the thiadiazole nitrogen atoms can Chemistry 2021, 3. Introduction of coordinating groups on the benzene ring affords neutral or anionic ligands allowing the formation of luminescent discrete complexes or coordination polymers in which the thiadiazole nitrogen atoms can take part, or not, to the coordination of metal centers [24]. Physical properties of the ZnII complexes are reported and compared to those of the ligands
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