A study of nerve agent model organophosphonate binding with manganese- A2B-corrole and - A2B2-porphyrin systems

Abstract

Herein the synthesis and binding studies of novel trans- A 2 B-corrole and trans- A 2 B 2-porphyrin derivatives are presented in comparing manganese(III)-organophosphonate (OP) binding (e.g., M n + ← O PR(OR) 2) capabilities. H 3(PFP-VC) [PFP-VC = 5,15-di(pentafluorophenyl)-10-(3-vinylphenyl)corrolate] was synthesized by way of literature procedures and was characterized by a variety of 2-D NMR spectroscopic techniques and single-crystal X-ray diffraction. These compounds represent the first example of 3-vinyl-phenyl-containing meso-substituted corroles or porphyrins. Mn(PFP-VC) ( 3) was treated separately with (CH 3CH 2O) 2P O(C 3H 6NMe 2), (C 4H 9O) 2P O(Me), (C 2H 5O) 2P O(CH 2COCH 3), (CH 3CH 2O) 2P O(Me), to give 1:1 adducts, as determined by UV–Vis spectroscopy (Job Plot), giving a red shift; Ph 3P O, was also found to bind, but very weakly. The trans- A 2 B 2-porphyrin analogue Mn(PFP-VP) ( 4) was also prepared by way of a literature procedure; related binding studies gave 1:1 organophosphonate-Mn(PFP-VP) adducts (Job Plot). A clean blue shift occurred for the Mn-porphyrins at higher organophosphonate loadings ( K a values: 6.7 (0.9)–11.9 (0.4) M −1). DFT geometry optimizations of O P(OMe) 2Me binding and formal Mn–O or P–O cleavage products in the unsubstituted neutral Mn-corrolato and -porphyrinato systems with a range of metal-based spin states revealed greatest stability in formal phosphoryl oxygen binding (energies: 11–13 kcal/mol) for the Mn-corrole ( singlet); the Mn-porphyrin ( sextet) was also quite stable.