title: Analysis of organophosphate-Zn metalloporphyrin interactions via UV-vis spectroscopy and molecular modeling.
abstract: UV-vis absorption spectra of zinc tetraphenylporphine (ZnTPP) on interaction with six organophosphorus (OP) compounds in cyclohexane were compared using ab initio methods and the molecular and solvation ligand descriptors π(*), Vx, and σ. OPs with polarizable hydrocarbon substituents in the homologous series tri-ethyl, -pentyl, -octyl, and -phenyl phosphates and the toxicologically relevant methyl paraoxon (1a-e) each gave a red shift in the Soret band (λsor) of ZnTPP in the range of 8-10 nm. Sensitivity as ΔAsor-b/Δug OP for the spectral band of the ligand bound ZnTPP (λsor-b) decreased with increasing extent of alkyl and aromatic substitution. Calculated and combined energies for OP and ZnTPP examined as a function of distance (Å) between ligand and porphyrin center suggest increased steric crowding with increasing Vx, and aromatic content of the OP. Spectrally fitted K1:1 and ΔAsor-b/ug OP each vary exponentially with Vx/σ. Lack of a red shift in λsor-b where ZnTPP was titrated with the toxic diethyl chlorophosphate (1g) is consistent with a model in which the magnitude of ΔEsor is proportional to the donor capacity of the phosphoryl-O ligand.
authors.affiliation: Dept. of Chemistry and Physical Sciences, Pace University, New York, NY, United States.
authors.forename: A
authors.initials: A
authors.lastname: Rompoti
authors.affiliation: Dept. of Chemistry and Physical Sciences, Pace University, New York, NY, United States.
authors.forename: N
authors.initials: N
authors.lastname: Dalal
authors.affiliation: Dept. of Chemistry and Physical Sciences, Pace University, New York, NY, United States.
authors.forename: D
authors.initials: D
authors.lastname: Athanasopoulos
authors.affiliation: Dept. of Chemistry, Virginia Commonwealth University, Richmond, VA, United States.
authors.forename: S
authors.initials: S
authors.lastname: Rutan
authors.affiliation: Dept. of Chemistry and Physics, St Francis College, Brooklyn Heights, NY, United States. Electronic address: rhelburn@sfc.edu.
authors.forename: R
authors.initials: R
authors.lastname: Helburn
mesh_terms: D008024:Ligands; D008665:Metalloporphyrins / Q000737:chemistry*; D008958:Models, Molecular; D010755:Organophosphates / Q000737:chemistry* / Q000633:toxicity; D012997:Solvents / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics
chemical_list: D008024:Ligands; D008665:Metalloporphyrins; D010755:Organophosphates; D012997:Solvents; C076448:zinc tetraphenylporphine
keywords: Ab initio; Metalloporphyrin; Organophosphosphorus; Solvation parameter; UV–vis absorption spectroscopy; ZnTPP