pectrophotometric studies of charge-transfer complexes formed with ions N,N'-alkyldiyl-bis(pyridinium) derivatives and iodid

Autor(es)

de Carvalho, Fernando Rodrigues ^[1] ; da Silva, Fernando ^[2] ; de Lima, Ricardo ^[2] ; Bellotto, Andrezza Correia ^[3] ; de Souza, Vagner Roberto ^[3] ; Caetano, Wilker ^[3] ; Politi, Mario Jose ^[4] ; Hioka, Noboru ^[1] ; Coutinho, Kaline ^[2]

Afiliação do(s) autor(es)

^[1] Univ Estadual Maringa, Dept Tecnol, Campus Reg Umuarama, BR-87506370 Umuarama, PR - Brazil

^[2] Univ Sao Paulo, Inst Fis, BR-05508090 Sao Paulo, SP - Brazil

^[3] Univ Estadual Maringa, Dept Quim, BR-87020900 Maringa, Parana - Brazil

^[4] Univ Sao Paulo, Inst Quim, BR-05508000 Sao Paulo, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY; v. 268, MAR 5 2022.
• Citações Web of Science: 0

Resumo

The charge-transfer complexes (CTC) between electron donor iodide and pyridinium dimers and monomers as acceptors have been studied spectrophotometrically in acetonitrile, DMSO and water. The dimers were: N,N'-alkyldiyl-bis(4-cyanopyridinium) and N,N'-alkyldiyl-bis(2-bromopyridinium), and the monomers were: N-alkyl-4-cyanopyridinium and N-alkyl-2-bromopyridinium, bridged by n methylene spacers. The formation constant (K-CTC), molar absorptivity (eCTC), fluorescence-quenching constant (K-SV) were determined. The results indicate that the stoichiometry of the CTC for dimers and monomers is 1:1 (equimolar ratio), and its formation is favored for dimers more than for monomers, especially dimers with short methylene spacers forming a ``sandwiched type-complex{''} in which the iodide is close to the two pyridinium rings. Solvents with low polarity favored the complex, which was destroyed by the presence of water. The experimental studies were complemented with theoretical studies with quantum mechanics (QM) calculations using density functional theory (DFT) and molecular mechanics (MM) simulations with Molecular Dynamics for identify the most stable conformers in acetonitrile solution. The electronic excitations were calculated with sequential QM/MM hybrid method, showing a charge transfer wavelength in agreement with the UV-Vis absorption spectra obtained experimentally. It confirms the ``sandwiched type-complex{''} conformers favoring the interaction of the iodide with one pyridinium rings and simultaneously forming one, or two, hydrogen bonds with the alkyl chain and addi-tionally, for the case of dimers, with the other pyridinium ring. (C) 2021 Elsevier B.V. All rights reserved. (AU)

• Processo FAPESP: 21/09016-3 - Caracterização estrutural e eletrônica de moléculas biogênicas emitidas pela flora amazônica
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