Interaction of Carotenoids and Cu²⁺in Cu-MCM-41:  Distance-Dependent Reversible Electron Transfer

Abstract

Carotenoids (Car), β-Carotene (I), 8′-apo-β-caroten-8′-al (II), and canthaxanthin (III), incorporated into activated Cu-MCM-41 were examined by UV/vis and EPR spectroscopies. A Cu 2+ -Car complex was formed for I and III but not for II. Formation of a complex results in distortion of the all-trans carotenoid geometry and a tetragonal geometry for Cu 2+ . The binding energies of Car and Cu 2+ , the changes in the maximum absorption, and the bond lengths of Car after the formation of the Cu 2+ -Car complex were examined by semiempirical ZINDO/1 and ZINDO/S calculations. Formation of a complex between Car and Cu 2+ favors both forward and back electron transfer (ET) reactions due to the short distance (∼2 Å) between Car and Cu 2+ , and reversible ET appears upon temperature cycling.

The Luminescence properties of coumarin-6 within Ti-HMS

“…It can be known from Table 1 that the absorption maxima of C6 in HMS shift to red about 30-40 nm compared with that in ethanol, and these red shifts can be explained by polarization of C6 molecules and environment around them [16]. We also know from Table 1 that the absorption maxima of C6 in Ti-HMS shift to blue over 10 nm compared with that in Si-HMS, indicating that C6 molecules interact with Ti 4+ [17]. The intensities decrease dramatically with increasing of Ti content in the samples, because the approach of C6 molecules due to the increasing of C6 amount will interact each other or forms C6 aggregate; and TiO 2 is formed in 2% and 10% Ti-HMS, so more and more C6 molecules are adsorbed on TiO 2 , leading to absorbance of C6 in 10% Ti-HMS is very weak.…”

Synthesis of a Highly Unsaturated, Stable Hydroxy Peroxide: A Yellow [lrarr2] Blue Color‐Changing Carotenoid Oxidation Product with Leuco Dye Properties

“…However, the typical NIR-absorption was not seen and carotenoid oxidation products were not separated. [44] We conclude by mentioning other reported reactions of carotenoids with iron. Addition of Fe 3+ to (hydroxy) carotenones gave stable carotenoid-Fe-chelate complexes with only a slight increase in absorption.…”

Microwave‐induced degradation of nitrosamines trapped in zeolites

“…Surface silanol groups played a crucial role in the adsorption by mesoporous silica because they were able to form hydrogen bond with the N atoms of amino groups and/or the O atom in the nitroso group of nitrosamines. [39] Dispersion of copper oxide on SBA-15 was at the expense of surface Si-OH for each copper cation reacted with three Si-OH groups, [40] so the MCS1 sample showed similar activity to SBA-15 and the highest performance emerged on the sample of MCS10 (Table 1). Through the comparison of MCSn and CSn sample, the influence of preparation on the copper modification could be seen.…”