Photocatalytic hydrogen production with dithiolenic complexes

This work was conducted within the graduate thesis in the laboratory ofInorganic Chemistry of Chemistry Department of National and KapodistrianUniversity of Athens. The first part is a review of the photo-catalytic systems forhydrogen production in homogeneous catalysis. We also present the synthesis andcharacterization of: [ReBr(CO)3(amphen)] (amphen = 1,10 – phenathroline – 5 –amine), [ReBr(CO)3(phendione)] (phendione = 1,10 – phenathroline – 5,6 – dione),[ReCl(CO)3amphen], [Re(CO)3Cl{dppz-3,6-(COOEt)2}] (dppz-3,6-(COOEt)2 = [3,2-a:2΄,3΄-c]phenazine-3,6- dicarboxylic ethyl ester). The X-ray crystal structure of[ReBr(CO)3pq] (2) has been determined. Electrochemical and photophysical studieshave been performed to study the ability of the [ReBr(CO)3amphen],[ReBr(CO)3(phendione)], [ReCl(CO)3(amphen)], [ReBr(CO)3pq], [Re(CO)3Cl{dppz3,6-(COOEt)2}],[Ga(di-o-F-p-py)-1-Ga], [Ga(tpfc)-2-Ga] and Cu(I) complexes{[Cu(I) (dppzCOOEt)2]} to reduce protons in homogeneous photocatalytic systems.Cobaloximes, dithiolenic complexes Ni, Co(II) complexes {[K(NCMe)3(L6)CoII-NCMe]∙MeCN∙H2O, [K(NCMe)3(L13)CoII-NCMe]} and Cu(I) complexes {[Cu(I)(dppzCOOEt)2]} were used as hydrogen reaction catalysts. The mechanism ofthe reactions were studied by quenching fluorescence experiments.Η παρούσα εργασία διενεργήθηκε στα πλαίσια της διδακτορικής διατριβής στο Εργαστήριο Ανόργανης Χημείας του Τμήματος Χημείας του Εθνικού και Καποδιστριακού Πανεπιστημίου Αθηνών. Καλύπτει βιβλιογραφικά φωτοκαταλυτικά συστήματα παραγωγής υδρογόνου ομογενούς κατάλυσης. Παρουσιάζεται η σύνθεση και ο χαρακτηρισμός των συμπλόκων : [ReBr(CO)3(amphen)] (amphen = 5 – άμινο -1,10 – φαινανθρολίνη), [ReBr(CO)3(phendione)] (phendione = 1,10 – φαινανθρολίνη– 5,6 – διόνη), [ReCl(CO)3(amphen)], [Re(CO)3Cl{dppz-3,6-(COOEt)2}] (dppz-3,6-(COOEt)2 = διπυριδο[3,2-a:2΄,3΄-c] φαιναζίνη-3,6- δικαρβοξυλαιθυλ εστέρας]). Επίσης παρουσιάζεται η κρυσταλλική δομή του συμπλόκου [ReBr(CO)3(pq)]. Τα σύμπλοκα: [ReBr(CO)3amphen], [ReBr(CO)3(phendione)], [ReCl(CO)3(amphen)],[ReBr(CO)3pq], [Re(CO)3Cl{dppz-3,6-(COOEt)2}], [Ga(di-o-F-p-py)-1-Ga],[Ga(tpfc)-2-Ga] και σύμπλοκο του Cu (I) {[Cu(I) (dppzCOOEt)2]} διερευνήθηκαν ως προς την ικανότατα τους να δρουν ως φωτοευαισθητοποιητές για να ανάγουν πρωτόνια σε ομογενή φωτοκαταλυτικά συστήματα. Ως καταλύτες για την μεταφορά πρωτονίων στο νερό χρησιμοποιήθηκαν κοβαλοξίμες, διθειολενικά σύμπλοκα του Ni,σύμπλοκα του Co(II) {[K(NCMe)3(L6)CoII-NCMe]∙MeCN∙H2O,[K(NCMe)3(L13)CoII-NCMe]} και σύμπλοκο του Cu (I) {[Cu(I)(dppzCOOEt)2]}. Στα πλαίσια της ερευνητικής εργασίας για την περιγραφή των φωτοκαταλυτικών μηχανισμών που λαμβάνουν χώρα, πραγματοποιήθηκαν πειράματα αποδιέγερσης του φωτοευαισθητοποιητή με προσθήκη καταλύτη

Synthesis, characterization and crystal structure of rhenium(I) tricarbonyl diimine complexes coupled with their efficiency in producing hydrogen in a photocatalytic system

Herein, we present the synthesis and characterization of two complexes, namely [ReBr(CO)3amphen] (1) (amphen = 1,10-phenanthroline-5-amine) and [ReBr(CO)3pq] (2) (pq = 2-(2′pyridyl)quinoxaline); complex 2 is reported for the first time. The X-ray crystal structure of 2 has been determined. Electrochemical and photophysical studies have been performed to study the effect of the variation of the diimine ligand on the redox and optical properties of this class of compounds. Both complexes were used as photosensitizers for hydrogen production in a homogeneous photocatalytic system also carrying [Co(dmgH)2] as a hydrogen reaction catalyst, triethanolamine as an irreversible reductive quencher and AcOH as proton source. Complex 1 produces H2 after only 2 h irradiation while complex 2 requires 24 h indicating that the differences in the electronic properties influence their photosensitizing ability

Global economic burden of unmet surgical need for appendicitis

Background There is a substantial gap in provision of adequate surgical care in many low- and middle-income countries. This study aimed to identify the economic burden of unmet surgical need for the common condition of appendicitis. Methods Data on the incidence of appendicitis from 170 countries and two different approaches were used to estimate numbers of patients who do not receive surgery: as a fixed proportion of the total unmet surgical need per country (approach 1); and based on country income status (approach 2). Indirect costs with current levels of access and local quality, and those if quality were at the standards of high-income countries, were estimated. A human capital approach was applied, focusing on the economic burden resulting from premature death and absenteeism. Results Excess mortality was 4185 per 100 000 cases of appendicitis using approach 1 and 3448 per 100 000 using approach 2. The economic burden of continuing current levels of access and local quality was US $92 492 million using approach 1 and$73 141 million using approach 2. The economic burden of not providing surgical care to the standards of high-income countries was $95 004 million using approach 1 and$75 666 million using approach 2. The largest share of these costs resulted from premature death (97.7 per cent) and lack of access (97.0 per cent) in contrast to lack of quality. Conclusion For a comparatively non-complex emergency condition such as appendicitis, increasing access to care should be prioritized. Although improving quality of care should not be neglected, increasing provision of care at current standards could reduce societal costs substantially

Global economic burden of unmet surgical need for appendicitis

Background There is a substantial gap in provision of adequate surgical care in many low- and middle-income countries. This study aimed to identify the economic burden of unmet surgical need for the common condition of appendicitis. Methods Data on the incidence of appendicitis from 170 countries and two different approaches were used to estimate numbers of patients who do not receive surgery: as a fixed proportion of the total unmet surgical need per country (approach 1); and based on country income status (approach 2). Indirect costs with current levels of access and local quality, and those if quality were at the standards of high-income countries, were estimated. A human capital approach was applied, focusing on the economic burden resulting from premature death and absenteeism. Results Excess mortality was 4185 per 100 000 cases of appendicitis using approach 1 and 3448 per 100 000 using approach 2. The economic burden of continuing current levels of access and local quality was US $92 492 million using approach 1 and$73 141 million using approach 2. The economic burden of not providing surgical care to the standards of high-income countries was $95 004 million using approach 1 and$75 666 million using approach 2. The largest share of these costs resulted from premature death (97.7 per cent) and lack of access (97.0 per cent) in contrast to lack of quality. Conclusion For a comparatively non-complex emergency condition such as appendicitis, increasing access to care should be prioritized. Although improving quality of care should not be neglected, increasing provision of care at current standards could reduce societal costs substantially