resumo
Electrospray mass spectrometry/mass spectrometry was used to investigate the gas-phase properties of protonated expanded porphyrins, in order to correlate those with their structure and conformation. We have selected five expanded meso-pentafluorophenyl porphyrins, respectively, a pair of oxidized/reduced fused pentaphyrins (22 and 24 p electrons), a pair of oxidized/reduced regular hexaphyrins (26 and 28 p electrons) and a regular doubly N-fused hexaphyrin (28 p electrons). The gas-phase behavior of the protonated species of oxidized and reduced expanded porphyrins is different. The oxidized species (aromatic Huckel systems) fragment more extensively, mainly by the loss of two HF molecules. The reduced species (Mobius aromatic or Mobius-like aromatic systems) fragment less than their oxidized counterparts because of their increased flexibility. The protonated regular doubly fused hexaphyrin (non-aromatic Huckel system) shows the least fragmentation even at higher collision energies. In general, cyclization through losses of HF molecules decreases from the aromatic Huckel systems to Mobius aromatic or Mobius-like aromatic systems to non-aromatic Huckel systems and is related to an increase in conformational distortion. Copyright (C) 2016 John Wiley & Sons, Ltd.
palavras-chave
NONLINEAR-OPTICAL PROPERTIES; MASS-SPECTROMETRIC ANALYSIS; MOBIUS AROMATICITY; METAL-COMPLEXES; CONFORMATION; HEXAPHYRINS(1.1.1.1.1.1); IDENTIFICATION; ELECTROSPRAY; DERIVATIVES; HEXAPHYRIN
categoria
Biochemistry & Molecular Biology; Chemistry; Spectroscopy
autores
Ramos, CIV; Figueira, F; Poleto, MD; Amado, FML; Verli, H; Tome, JPC; Neves, MGPMS
nossos autores
Flávio Alberto da Silva Figueira
Investigador Júnioragradecimentos
The authors wish to express their appreciation to Doctor M. Graca Santana-Marques for all the helpful and valuable discussions. Thanks are because of FCT/MEC for the financial support to the QOPNA (FCT UID/QUI/00062/2013) and CQE (FCT UID/QUI/0100/2013) research units, through national funds and where applicable co-financed by the FEDER (Fundo Europeu de Desenvolvimento Regional), within the PT2020 Partnership Agreement, and also to the Portuguese NMR Network. Thanks are also because of the Brazilian CAPES (Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior), CNPq (Conselho Nacional de Desenvolvimento Cientifico e Tecnologico) and FAPERGS (Fundacao de Amparo a Pesquisa do Rio Grande do Sul) funding agencies. Catarina I. V. Ramos and Flavio Figueira thank FCT (Fundacao para a Ciencia e Tecnologia) for their scholarships SFRH/BPD/85902/2012 and SFRH/BD/46788/2008, respectively.