Utilize este identificador para referenciar este registo: http://hdl.handle.net/10400.21/531
Título: Synthesis, structure, and optical properties of an alternating calix[4]arene-based meta-linked phenylene ethynylene copolymer
Autor: Barata, Patrícia Alexandra David
Costa, Alexandra I.
Ferreira, Luis F. V.
Prata, José Virgílio
Palavras-chave: Calixarene
Fluorescence
Intramolecular exciplex
Meta-linked
Phenylene ethynylene polymer
Data: 15-Nov-2010
Editora: John Wiley & Sons INC
Citação: Barata P, Costa A, Ferreira L, Prata J.Synthesis, Structure, and Optical Properties of an Alternating Calix[4]arene-Based Meta-Linked Phenylene Ethynylene Copolymer. Journal of Polymer Science Part A-Polymer Chemistry. 2010; 48 (22): 5040-5052.
Relatório da Série N.º: 22
Resumo: Novel alternating copolymers comprising biscalix[4]arene-p-phenylene ethynylene and m-phenylene ethynylene units (CALIX-m-PPE) were synthesized using the Sonogashira-Hagihara cross-coupling polymerization. Good isolated yields (60-80%) were achieved for the polymers that show M-n ranging from 1.4 x 10(4) to 5.1 x 10(4) gmol(-1) (gel permeation chromatography analysis), depending on specific polymerization conditions. The structural analysis of CALIX-m-PPE was performed by H-1, C-13, C-13-H-1 heteronuclear single quantum correlation (HSQC), C-13-H-1 heteronuclear multiple bond correlation (HMBC), correlation spectroscopy (COSY), and nuclear overhauser effect spectroscopy (NOESY) in addition to Fourier transform-Infrared spectroscopy and microanalysis allowing its full characterization. Depending on the reaction setup, variable amounts (16-45%) of diyne units were found in polymers although their photophysical properties are essentially the same. It is demonstrated that CALIX-m-PPE does not form ground-or excited-state interchain interactions owing to the highly crowded environment of the main-chain imparted by both calix[4]arene side units which behave as insulators inhibiting main-chain pi-pi staking. It was also found that the luminescent properties of CALIX-m-PPE are markedly different from those of an all-p-linked phenylene ethynylene copolymer (CALIX-p-PPE) previously reported. The unexpected appearance of a low-energy emission band at 426 nm, in addition to the locally excited-state emission (365 nm), together with a quite low fluorescence quantum yield (Phi = 0.02) and a double-exponential decay dynamics led to the formulation of an intramolecular exciplex as the new emissive species.
Peer review: yes
URI: http://hdl.handle.net/10400.21/531
ISSN: 0887-624X
Aparece nas colecções:ISEL - Eng. Quim. Biol. - Artigos



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