Photophysics and Photochemistry of Conformationally Restricted Triarylmethanes: Application as Photoredox Catalysts

The three aryl rings of triarylmethanes are free to rotate. However this free rotation can be restricted on either by bridging the aryl rings through covalent bonds or through heteroatoms resulting in the formation of Conformationally Restricted Triarylmethanes (CRT). The photophysics and photochemistry of these CRTs, like 9-arylxanthenes (oxygen bridging), 9-arylthioxanthenes (sulfur bridging), 9, 10-dihydro-9-arylacridines (nitrogen bridging), 9-arylfluorenes (bridging through carbon–carbon covalent bond) have recently been the subject of number studies. Various applications of CRT molecules have been developed out of which application as photoredox catalyst is undoubtedly the most important. In this chapter, we have highlighted recent development of various CRT molecules, their photophysics, photochemistry and an application in the field of photoredox catalysis

Metal nanoparticle alters adenine induced charge transfer kinetics of vitamin K3 in magnetic field

In this article, we highlight the alterations in the photoinduced electron transfer (ET) and hydrogen atom transfer (HAT) pathways between an anti-tumor drug vitamin-K3 (MQ) and a nucleobase adenine (ADN) in the presence of gold (Au) and iron (Fe) nanoparticles (NPs). Inside the confined micellar media, with laser flash photolysis corroborated with an external magnetic field (MF), we have detected the transient geminate radicals of MQ and ADN, photo-generated through ET and HAT. We observe that the presence of AuNP on the MQ-ADN complex (^(Au)MQ-ADN) assists HAT by limiting the ET channel, on the other hand, FeNP on the MQ-ADN complex (^(Fe)MQ-ADN) mostly favors a facile PET. We hypothesize that through selective interactions of the ADN molecules with AuNP and MQ molecules with FeNP, a preferential HAT and PET process is eased. The enhanced HAT and PET have been confirmed by the escape yields of radical intermediates by time-resolved transient absorption spectroscopy in the presence of MF

Photochemistry and Photophysics - Fundamentals to Applications

Photochemistry and photophysics are as old as our planet Earth. Photosynthesis in plants and vision in our eyes are natural examples of their importance. This book entitled ""Photochemistry and Photophysics - Fundamentals to Applications"" presents various advanced topics that inherently utilize core concepts of photochemistry and photophysics. There are eleven chapters in this book, which are divided into four 'parts'. While the first and second parts contain chapters describing the fundamentals of photochemistry and photophysics, respectively, the third part is on computational photochemistry. The last part deals with applications of photochemistry and photophysics. The goal of this book is to familiarize both research scholars and postgraduate students with recent advances in this exciting field

Tandem Cooperative Friedel-Crafts Reaction of Aldehydes with Electron Deficient Arenes Through Catalyst-Activation via Hydrogen Bonding Network

Since its discovery in 1877, the Friedel-Crafts alkylation reaction has been the method of choice to prepare various aryl hydrocarbons. Recent developments for this reaction have resulted in the synthesis of these compounds in one pot process with various metal as well as metal free protocols. However, the alkylation of common feedstock aldehydes using electron-deficient arenes and also with two different arene nucleophiles are quite challenging and scantily explored. Herein, we provide a solution to these problems by a new concept, “catalyst activation” accomplished by increasing the Brønsted acidity of p-toluenesulfonic acid (pTSA) through strong hydrogen bonding with hexafluoroisopropanol (HFIP). The real-time NMR titration, as well as computational studies, reveal multiple roles of HFIP in increasing the Brønsted acidity of para-toluene sulphonic acid (pTSA) and stabilization of the transition states formed during the electrophilic aromatic substitution. The developed process has a great potential for industrial application reflected in the synthesis of various bio-active natural products like arundine, tartarinoid C, and several other bioactive molecules. Also, the used HFIP was recovered in a gram-scale synthesis making this protocol highly cost-effective and conducive to industrial production

Metal nanoparticle alters adenine induced charge transfer kinetics of vitamin K3 in magnetic field

In this article, we highlight the alterations in the photoinduced electron transfer (ET) and hydrogen atom transfer (HAT) pathways between an anti-tumor drug vitamin-K3 (MQ) and a nucleobase adenine (ADN) in the presence of gold (Au) and iron (Fe) nanoparticles (NPs). Inside the confined micellar media, with laser flash photolysis corroborated with an external magnetic field (MF), we have detected the transient geminate radicals of MQ and ADN, photo-generated through ET and HAT. We observe that the presence of AuNP on the MQ-ADN complex (^(Au)MQ-ADN) assists HAT by limiting the ET channel, on the other hand, FeNP on the MQ-ADN complex (^(Fe)MQ-ADN) mostly favors a facile PET. We hypothesize that through selective interactions of the ADN molecules with AuNP and MQ molecules with FeNP, a preferential HAT and PET process is eased. The enhanced HAT and PET have been confirmed by the escape yields of radical intermediates by time-resolved transient absorption spectroscopy in the presence of MF