Electron Affinities of Heavier Phosphoryl and Thiophosphoryl Halides APX 3 (A 5 O, S and X 5 Br, I) T. ZENG, 1 Z. JAMSHIDI, 2 H. MORI, 3 E. MIYOSHI, 3 M. KLOBUKOWSKI 1 1 Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2 2 Chemistry Department, College of Science, Shiraz University, Iran 3 Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasuga Park, Fukuoka 816-8580, Japan Received 14 November 2006; Revised 31 January 2007; Accepted 13 February 2007 DOI 10.1002/jcc.20726 Published online 23 April 2007 in Wiley InterScience (www.interscience.wiley.com). Abstract: We carried out computational studies of OPX 3 and SPX 3 (X ¼ Br and I) molecules and their corre- sponding anions using density functional theory, Møller-Plesset, and CCSD(T) methods with newly developed model core potentials (MCP). Reliabilities of the MCP were demonstrated by comparing experimental and calculated results. We computed the geometric structure, electron affinities, and electrostatic moments using systematic sequen- ces of the dzp-, tzp-, and qzp-quality basis sets. Both C 3v and C s symmetries were assumed to ascertain that minima on the potential energy surface were found. Infrared and Raman frequencies were calculated and compared with available experimental data. Natural population analyses were performed and used to determine distribution of the extra electron in anions. q 2007 Wiley Periodicals, Inc. J Comput Chem 28: 2027–2033, 2007 Key words: (thio-) phosphoryl halide; electron affinity; model core potential Introduction Phosphoryl and thiophosphoryl halides (APX 3 ,A ¼ O, S and X ¼ halogens) are important chemicals in both industry and laboratory as pesticides and insecticides. 1,2 They are also used as reactants and intermediates for the synthesis of phosphate esters and organophosphate derivatives. 3,4 Given their chemical importance, they have been extensively studied both experimen- tally and theoretically. Most of those studies were devoted to the exploration of geometrical and electronic structures of (thio-) phosphoryl halides and their changes during reaction processes to explain mechanisms of reactions involving the halides. With recent developments of computational quantum chemis- try, high-quality calculations on (thio-) phosphoryl halides became possible, and deeper insights into structures and spectra of these molecules were published. 3,5–7 In the past decade, sev- eral studies of electron attachment to OPCl 3 and SPCl 3 were reported. 8–11 It may be expected that more studies of electron attachment to the APX 3 systems will be carried out. In the present article, we used high quality quantum chemis- try methodology to study OPBr 3 , OPI 3 , SPBr 3 , and SPI 3 mole- cules and corresponding anions to perform geometry optimiza- tion and harmonic vibrational analysis and to compute electron affinities. Electron distribution was studied by the means of nat- ural population analysis. We anticipate that the present theoreti- cal analysis will assist experimental work in the future. Methodology Geometry optimizations, vibrational calculations, and natural population analyses (NPA) were carried out using GAMESS-US program 12 ; coupled-cluster single-point energy calculations were carried out using MOLCAS 13 ; visualization of orbitals and elec- tron density were carried out using MOLDEN. 14 All eight spe- cies (four neutral and four anionic systems) were optimized using both the density functional theory (DFT) with the B3LYP function 15–19 and the second-order Møller-Plesset (MP2) method 20–24 with the ZAPT method for the open-shell systems. Harmonic vibrational frequency analysis was performed to con- firm that the predicted structures corresponded to minima on the potential energy surfaces. The coupled-cluster method CCSD(T), 25 as implemented in MOLCAS, was employed to calculate single- point energy at the geometries predicted by MP2 and to predict electron affinities with better accuracy. Three newly developed model core potentials (MCP), 26 referred to as mcp- dzp, mcp-tzp, and mcp-qzp, were employed to eliminate core electrons and reduce basis set superposition Contract/grant sponsor: Natural Sciences and Engineering Research Council (NSERC), Alberta Ingenuity Fund Correspondence to: M. Klobukowski; e-mail: mariusz.klobukowski@ ualberta.ca q 2007 Wiley Periodicals, Inc.