TY - JOUR
T1 - Chemistry and Photochemistry of 2,6-Bis(2-hydroxybenzilidene)cyclohexanone
AU - Moro, A. J.
AU - Pana, Ana-Maria
AU - Cseh, Liliana
AU - Costisor, Otilia
AU - Parola, António Jorge Dias
AU - Cunha-Silva, L.
AU - Puttreddy, Rakesh
AU - Rissanen, Kari
AU - Pina, Fernando Jorge da Silva
N1 - Fundacao para a Ciencia e Tecnologia is acknowledged through the National Portuguese NMR Network, Grant PEst-C/EQB/LA0006/2013 and Post-Doc grant SFRH/BPD/69210/2010. The financial support of European Union COST Action CM1005 is gratefully acknowledged. The Romanian authors acknowledge the support of the Romanian Academy, Project 3.1.
PY - 2014/8
Y1 - 2014/8
N2 - The kinetics and thermodynamics of the 2,6-bis(2-hydroxybenzilidene)cyclohexanone chemical reactions network was studied at different pH values using NMR, UV-vis, continuous irradiation, and flash photolysis. The chemical behavior of the system partially resembles anthocyanins and their analogue compounds. 2,6-Bis(2-hydroxybenzilidene)cydohexanone exhibits a slow color change from yellow to red styrylflavylium under extreme acidic conditions. The rate constant for this process (5 x 10(-5) s(-1)) is pH independent and controlled by the cis-trans isomerization barrier. However, the interesting feature is the appearance of the colorless compound, 7,8-dihydro-6H-chromeno[3,2-d]xanthene, isolated from solutions of acid to neutral range, characterized by H-1 NMR and single crystal X-ray diffraction. Light absorption by 2,6-bis(2-hydroxybenzilidene)cyclohexanone solutions immediately after preparation exclusively results in cis-isomer as photoproduct, which via hemiketal formation yields (i) red styrylflavylium by dehydration under extremely acidic solutions (pH < 1) and (ii) colorless 7,8-dihydro-6H-chromeno[3,2-4canthene by cyclization in solutions of acid to neutral range.
AB - The kinetics and thermodynamics of the 2,6-bis(2-hydroxybenzilidene)cyclohexanone chemical reactions network was studied at different pH values using NMR, UV-vis, continuous irradiation, and flash photolysis. The chemical behavior of the system partially resembles anthocyanins and their analogue compounds. 2,6-Bis(2-hydroxybenzilidene)cydohexanone exhibits a slow color change from yellow to red styrylflavylium under extreme acidic conditions. The rate constant for this process (5 x 10(-5) s(-1)) is pH independent and controlled by the cis-trans isomerization barrier. However, the interesting feature is the appearance of the colorless compound, 7,8-dihydro-6H-chromeno[3,2-d]xanthene, isolated from solutions of acid to neutral range, characterized by H-1 NMR and single crystal X-ray diffraction. Light absorption by 2,6-bis(2-hydroxybenzilidene)cyclohexanone solutions immediately after preparation exclusively results in cis-isomer as photoproduct, which via hemiketal formation yields (i) red styrylflavylium by dehydration under extremely acidic solutions (pH < 1) and (ii) colorless 7,8-dihydro-6H-chromeno[3,2-4canthene by cyclization in solutions of acid to neutral range.
KW - FLAVYLIUM ION
KW - ISOMERIZATION
KW - HYDRATION
U2 - 10.1021/jp505533b
DO - 10.1021/jp505533b
M3 - Article
C2 - 25058169
SN - 1089-5639
VL - 118
SP - 6208
EP - 6215
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
IS - 32
ER -