Synthesis and molecular structure of perhalogenated rhenium-oxo corroles

Abstract

As part of our efforts to develop rhenium-oxo corroles as photosensitizers for oxygen sensing and photodynamic therapy, we investigated the potential β-perhalogenation of five ReO meso-tris(para-X-phenyl)corroles, Re[TpXPC](O) (X = CF3, H, F, CH3, and OCH3), with elemental chlorine and bromine. With Cl2, β-octachlorinated products Re[Cl8TpXPC](O) were rapidly obtained for X = CF3, H, and CH3, but X = OCH3 resulted in overchlorination on the meso-aryl groups. Full β-octabromination proved slower relative to Cu and Ir corroles, but the desired Re[Br8TpXPC](O) products were finally obtained for X = H and F after a week at room temperature. For X = CH3 and OCH3, these conditions led to undecabrominated products Re[Br11TpXPC](O). Compared to the β-unsubstituted starting materials, the β-octahalogenated products were found to exhibit sharp 1H NMR signals at room temperature, indicating that the aryl groups are locked in place by the β-halogens, and substantially redshifted Soret and Q bands. Single-crystal X-ray structures of Re[Cl8TpCF3PC](O), Re[Cl8TpCH3PC](O), and Re[Br8TpFPC](O) revealed mild saddling for one Cl8 structure and the Br8 structure. These structural variations, however, appear too insignificant to explain the slowness of the β-octabromination protocols, which seems best attributed to the deactivating influence of the high-valent Re center.

Phenol- and resorcinol-appended metallocorroles and their derivatization with fluorous tags

“…Synthesis of phenol-and resorcinol-appended metallocorroles. Rhenium-oxo [48][49][50][51][52][53] and gold [54][55][56][57][58][59][60][61][62][63] tris(4-methoxyphenyl)corrole, M[TpOMePC] (M = ReO, Au), and tris(3,5-dimethoxyphenyl)corrole, M[T(3,5-OMe)PC] (M = ReO, Au), which rank among the most readily accessible 5d metallocorroles [64][65][66][67][68][69] , were used as starting materials. The choice of the two metals was dictated by the fact that they yield rugged, electronically innocent complexes that have been shown to act as triplet photosensitizers in oxygen sensing and in vitro photodynamic therapy experiments.…”

“…1 Instrumental methods. The instrumentation used was essentially the same as in our earlier work [50][51][52][53] .…”

Regioselective formylation of rhenium-oxo and gold corroles: substituent effects on optical spectra and redox potentials

“…X-ray quality crystals were obtained via slow diffusion of methanol vapor into concentrated dichloromethane solutions of the compounds in question. X-ray data were collected (as previously described 37 ) on beamline 12.2.1 at the Advanced Light Source, Lawrence Berkeley National Laboratory. Samples were mounted on MiTeGen Kapton loops and placed in a 100(2)-K nitrogen cold stream provided by an Oxford Cryostream 800 Plus low-temperature apparatus on the goniometer head of a Bruker D8 diffractometer equipped with a PHOTON II CPAD detector operating in shutterless mode.…”

“…[25][26][27] In contrast (compared to 3d metallocorroles, 28,29 especially Cu corroles [30][31][32][33][34] ), the chemical reactivity of the 5d complexes remains poorly explored. Peripheral functionalizations accomplished so far include b-perchlorination 35 and perbromination, 36,37 as well as polyiodinations. 38,39 Metal-centered transformations include the generation of Mo and Re Viking-helmet dichlorido derivatives from the corresponding oxido precursors.…”

The Story of 5d Metallocorroles: From Metal–Ligand Misfits to New Building Blocks for Cancer Phototherapeutics

“…Exposure to elemental bromine over several days affords β-perbrominated derivatives. β-Perchlorination with elemental chlorine is much quicker, occurring over minutes . Vilsmeier–Haack formylation (with DMF/POCl 3 ) also occurs smoothly, affording 3-formyl products in a highly regioselective manner.…”