Green synthesis of organopalladium photosensitizers

Abstract

Razvijanje čišćih, bržih i ekonomski isplativijih preparativnih metoda za različite vrsta spojeva jedan je od ciljeva zelene i održive kemije. Izvedivost ovog koncepta zelene kemije prikazana je na sintezi organopaladijevih spojeva (paladocikla), važnih zbog njihove široke primjene u organskoj sintezi i jedinstvenih optičkih svojstava. Shodno tome, većina sintetskih koraka u ovom radu provedena je reakcijama u čvrstom stanju primjenom metoda mehanokemije ili ubrzanog starenja. Paladocikli s jednom ili dvije veze metal–ugljik i metal–donor dobiveni su aktivacijom veze(a) C–H u azobenzenima različitim katalizatorima paladija(II), a izmjena njihovih anionskih ili neutralnih liganada rezultirala je u derivatima s drugačijom reaktivnošću i optičkim svojstvima. Opisane reakcije praćene su in situ i ex situ spektroskopskim metodama što je omogućilo karakterizaciju vrsta uključenih u reakcije, izravan uvid u dinamiku i reakcijske putove, uvid u faktore koji kontroliraju reaktivnost i selektivnost, te optimizaciju procesa mljevenja. Ovi rezultati omogućit će primjenu razvijenih metoda i koncepata u sintezi novih organopaladijevih spojeva u okolišu prihvatljivim reakcijskim uvjetima, u izravnoj i selektivnoj zamjeni veze C–H drugim funkcionalnim skupinama, te u razvoju novih katalizatora.The development of clean, fast, and cost-effective preparative methods for various types of compounds is one of the objectives of green chemistry. The feasibility of this green chemistry concept was demonstrated on the synthesis of organopalladium compounds (palladacycles), important due to their wide application in organic synthesis and unique optical properties. Consequently, the majority of synthetic steps in this thesis were performed by solid-state synthetic method, mechanochemistry and accelerated aging. Palladacycles with one or two metal-carbon and metal-donor bonds were prepared via C–H bond(s) activation in azobenzenes by various Pd(II) catalysts, and the exchange of their anionic or neutral ligands resulted in derivatives with different reactivity and optical properties. The described reactions were monitored in situ and ex situ by spectroscopic methods, which enabled the characterization of the species involved in the reactions, direct insight into the reaction pathways, insight into the factors controlling reactivity and selectivity, and optimization of the grinding process. These results will enable the application of developed methods and concepts in the synthesis of new organopalladium compounds, in the direct and selective replacement of the C–H bond by other functional groups, and in the development of new catalysts