TY - JOUR
T1 - Phenolic-type stabilizers as generators and quenchers of singlet molecular oxygen (O2(1Δg)). Part I
T2 - methyl salicylate, salicylic acid and some related compounds
AU - Soltermann, Arnaldo T.
AU - de la Peña, Daniel
AU - Nonell, Santiago
AU - Amat-Guerri, Francisco
AU - García, Norman A.
N1 - Funding Information:
Thanks are given to CONICET, CONICOR and SECyT (UNRC) of Repdblica Argentina for financial support. Part of this work was developed during a sabbatical of N. A. G., financed by the Ministerio de Education y Ciencia (Spain).
PY - 1995
Y1 - 1995
N2 - The generation and quenching of singlet molecular oxygen by the widely employed photostabilizer methyl salicylate have been studied in several fluid solvents at room temperature. For comparative purposes, the following related compounds were also studied: methyl 2-methoxybenzoate, methyl 4-hydroxybenzoate, methyl 3-hydroxybenzoate, salicylic acid, 5-methylsalicylic acid and 5-nitrosalicylic acid. The results indicate that the compounds with a phenol group are inefficient O2(1Δg) generators upon direct (337 nm) irradiation, and that in contrast, the phenol-methylated ester methyl 2-methoxy benzoate produces O2(1Δg) with a quantum yield of 0.24 using MeCN-EtOH 4:1 as a solvent. Under adequate environmental conditions of medium polarity and pH, all the compounds are effective O2(1Δg) scavengers, with rate constants for the interaction with O2(1Δg) in the range 107-108 M-1 s-1. Both overall quenching and chemical reaction with O2(1Δg) are favoured in highly polar solvents or in the presence of bases, confirming the previously proposed mechanism through charge-transfer species. The presence of an intramolecular H-bond in salicylic acid, 5-methylsalicylic acid, 5-nitrosalicylic acid and methyl salicylate does not exert any influence on their interaction with O2(1Δg). With the exception of methyl 2-methoxybenzoate, the rest of the compounds studied here can be used as efficient dopant agents against O2(1Δg)-mediated degradation of photoprotected materials.
AB - The generation and quenching of singlet molecular oxygen by the widely employed photostabilizer methyl salicylate have been studied in several fluid solvents at room temperature. For comparative purposes, the following related compounds were also studied: methyl 2-methoxybenzoate, methyl 4-hydroxybenzoate, methyl 3-hydroxybenzoate, salicylic acid, 5-methylsalicylic acid and 5-nitrosalicylic acid. The results indicate that the compounds with a phenol group are inefficient O2(1Δg) generators upon direct (337 nm) irradiation, and that in contrast, the phenol-methylated ester methyl 2-methoxy benzoate produces O2(1Δg) with a quantum yield of 0.24 using MeCN-EtOH 4:1 as a solvent. Under adequate environmental conditions of medium polarity and pH, all the compounds are effective O2(1Δg) scavengers, with rate constants for the interaction with O2(1Δg) in the range 107-108 M-1 s-1. Both overall quenching and chemical reaction with O2(1Δg) are favoured in highly polar solvents or in the presence of bases, confirming the previously proposed mechanism through charge-transfer species. The presence of an intramolecular H-bond in salicylic acid, 5-methylsalicylic acid, 5-nitrosalicylic acid and methyl salicylate does not exert any influence on their interaction with O2(1Δg). With the exception of methyl 2-methoxybenzoate, the rest of the compounds studied here can be used as efficient dopant agents against O2(1Δg)-mediated degradation of photoprotected materials.
UR - https://www.scopus.com/pages/publications/0029492772
UR - https://www.webofscience.com/api/gateway?GWVersion=2&SrcApp=pure_univeritat_ramon_llull&SrcAuth=WosAPI&KeyUT=WOS:A1995TF22500007&DestLinkType=FullRecord&DestApp=WOS
U2 - 10.1016/0141-3910(95)00112-Y
DO - 10.1016/0141-3910(95)00112-Y
M3 - Article
AN - SCOPUS:0029492772
SN - 0141-3910
VL - 49
SP - 371
EP - 378
JO - Polymer Degradation and Stability
JF - Polymer Degradation and Stability
IS - 3
ER -