Benzoquinolateplatinum(II) complexes as building blocks in the synthesis of Pt-Ag extended structures

 
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Benzoquinolateplatinum(II) complexes as building blocks in the synthesis of Pt-Ag extended structures (EN)

Fornies, J. (EN)

Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας (EL)
Fornies, J. (EN)

The reaction between (NBu4)[Pt(bzq)(C6F5)2] (1, bzq = 7,8-benzoquinolate) and AgClO4 in a 1 : 1 molar ratio, in acetone, gives the polymer [{Pt(bzq)(C6F5)2}Ag]n (2). The reaction of 2 with equimolecular amounts of PPh3 and SC4H8 (tht) produces the bimetallic complexes [{Pt(bzq)(C6F5)2}AgL] (L = PPh3 (3), tht (4)). For L = py, decomposition takes place and [Pt(bzq)(C6F5)py] (5) is obtained. All these complexes have been characterized by X-ray diffraction. The most interesting features of complexes 2-4 is the presence of Pt-Ag bonds, with Pt-Ag distances of ca. 2.75 Å. Besides, the silver centres establish short η1 bonding interactions with the Cipso of the bzq ligands, with distances Ag-C of ca. 2.45 Å. Complex 2 is a one-dimensional infinite chain in which the fragments "�Pt(bzq)(C6F5)2�"� and Ag+ alternate. On the other hand, complexes 1 and 3-5 show intermolecular pairing through ππ interactions between the aromatic rings of the bzq ligand, having interplanar separations of ca. 3.5 Å. Complex 2 dissolves in donor solvents (acetone, THF) as discrete bimetallic solvated fragments [{Pt(bzq)(C6F5)2}AgSn] (S = solvent), similar to complexes 3 and 4. The persistence of the Pt-Ag bond in 2-4, supported by multinuclear NMR spectroscopy, causes a significant blue-shift in the lowest-lying absorption in relation to 1. This fact is attributed (TD-DFT) to a remarkable modification of the orbitals contributing to the HOMO, which changes the character of the transition from 1LC/1MLCT in 1 to admixture 1L'LCT/1MLCT in the bimetallic complexes. The low energy feature (490-530 nm) of 2 in solid state is attributed to CT from the Pt fragments to the Ag centers. Complexes 2-4 are only emissive in rigid media (solid and glasses). In the solid state, the metallic chain 2 exhibits a bright orange emission (560 nm, 298 K; 590 nm, 77 K), assigned to an excited state involving charge transfer from the platinum fragment with a remarkable contribution of C6F5 (Arf) rings to the Pt-Ag bond (3LMM'CT/3L'M'CT). However, 3 and 4 exhibit in solid state at 298 K a vibronic band, which is clearly resolved in two close non-equilibrated bands at 77 K in 3, tentatively ascribed to a mixture of 3MLCT/3L'LCT transitions modified by the formation of the Pt-Ag bond. In glassy solution (77 K) 2-4 display a vibronic emission ascribed primarily to 3LC character. (EN)

Πανεπιστήμιο Ιωαννίνων (EL)
University of Ioannina (EN)

Dalton Transactions (EN)

Αγγλική γλώσσα

2012


Royal Society of Chemistry (EN)



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