Corroles as a Platform for Fundamental Transition Metal Chemistry, with Emphasis on Heavy Elements

Hemoglobin - den røde fargen i blod - og klorofyll - den grønne fargen i planter - består begge av ringformede organiske molekyler med et metallatom i midten. I vårt laboratorium har vi fremstilt kunstige versjoner av disse molekylene med vesentlig større atomer i midten, som for eksempel gull, osmium og rhenium. Denne typen fremstilling har involvert ganske komplisert "molekylakrobatikk", og dette er i seg selv av grunnleggende vitenskapelig interesse, men de nye molekylene har også vist seg å være nyttige i flere sammenhenger. Spesielt har deres vekselvirkning med lys vært interessant: Dette satte molekylene i langlivede høyenergitilstander - såkalte eksiterte tilstander. Dette fenomenet kalles fosforescens og kan observeres i dagliglivet som det som skaper lyset i selvlysende materialer - for eksempel til bruk som preg på t-skjorter. Disse nye fargestoffene viste seg å være nyttig i kjemoterapeutisk behandling av kreft under påvirkning av lysstråler - såkalt fotodynamisk terapi - så vel som til bruk i en ny type solcelle som baserer seg på fosforiserende fargestoffer. Det arbeides for tiden intenst med tilsetting av radioisotoper som 99mTc og 64Cu for å lage nye teranostikk-midler, dvs., molekyler som kan brukes til både terapi og diagnostikk.

Three well-defined goals will be pursued, all linked by our interest in fundamental aspects of transition metal electronic structure and reaction mechanisms, as well as our practical expertise in porphyrin/corrole chemistry. 1. A large body of crystallog raphic work in our laboratory has shown that copper corroles are inherently nonplanar and chiral (on electronic grounds), but to date they have only been prepared in racemic form. Both chiral resolution and chiral synthesis will be employed to synthesize copper corroles as pure enantiomers. Once synthesized, the enantiomers will be extensively studied via various chiroptical spectroscopies and also theoretically modeled. 2. The compressed, trianionic core of corroles provides a little studied environment for heavy elements. Recent successes in the synthesis of Ir and Au corroles have encouraged a search for Pt corroles, which are of interest because of their potential for reactivity at the axial sites. According to the literature, such efforts have so fa r been unsuccessful. Very recently, however, the first platinum corroles have been synthesized in our laboratory and the first crystal structure obtained, laying the foundation of a major exploration of structure-property relationships of these complexes. Once such a knowledge base is in place, we will increasingly move our attention to chemical reactivity and catalysis, particularly in relation to C-H and C-F activation. 3. Iridium corroles have been reported in the literature, but the higher-valent sta tes remain little explored. For oxo/imido/nitrido complexes, such states are likely to be highly reactive, being on the "wrong" side of the so-called oxo wall. With undecaarylcorroles and other highly sterically hindered ligands, however, we hope to kinet ically trap such species and study their structures and reactivity. It will be of great interest to compare these complexes/intermediates with more stable, low-coordinate complexes such as Mes3IrO (Mes = mesit