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An Ab Initio Investigation of the Ground States of FP(S)N, FPNS, and FPSN Jiwon Moon, Heehyun Baek, and Joonghan Kim J. Phys. Chem. A, Just Accepted Manuscript • DOI: 10.1021/acs.jpca.6b09647 • Publication Date (Web): 03 Nov 2016 Downloaded from http://pubs.acs.org on November 4, 2016

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The Journal of Physical Chemistry

An Ab Initio Investigation of the Ground States of F2P(S)N, F2PNS, and F2PSN Jiwon Moon, Heehyun Baek, and Joonghan Kim* Department of Chemistry, The Catholic University of Korea, Bucheon 14662, Republic of Korea

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ABSTRACT A recent spectroscopic experiment identified difluorothiophosphoryl nitrene (F2P(S)N) and found that it showed rich photochemistry. However, a discrepancy between the experimental results and the quantum chemical calculations was reported. Thus, highlevel ab initio calculations using the coupled-cluster singles and doubles with perturbative triples and second-order multiconfigurational perturbation theory were performed to elucidate this inconsistency. The discrepancy arose due to the failure to consider the triplet state of difluoro(thionitroso)phosphine (F2PNS). In this work, we identify the global minimum of the system is the triplet state of F2PNS, which allows us to explain the inconsistency between the experimental and theoretical results. All calculated results give consistent results with the recent experimental results.


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1. Introduction A recent spectroscopic experiment identified the simplest thiophosphoryl nitrene compound, difluorothiophosphoryl nitrene (F2P(S)N), and found that it showed rich photochemistry.1 Subsequent visible-light irradiation (≥495 nm) resulted in the transformation of F2P(S)N to difluoro(thionitroso)phosphine (F2PNS). Further irradiation of F2PNS at 365 nm caused re-formation of F2(P)SN and transformation to its thiazyl type isomer (F2PSN), indicating that two photochemical channels were active. These three intermediates (F2P(S)N, F2PNS, and F2PSN) were characterized by infrared and UV-vis spectroscopy in matrix environments. In addition, high-level ab initio calculations using coupled-cluster singles and doubles with perturbative triples (CCSD(T)) were also performed to support the experimental observations. However, only the singlet states of F2PNS and F2PSN were considered in this previous study.1 Because the CCSD(T) method is quite reliable,2 vibrational frequencies calculated by CCSD(T) are in excellent agreement with experimental results even without considering anharmonic effects. Indeed, the vibrational frequencies of the singlet states of F2(P)SN and F2PSN calculated by CCSD(T) were well matched with those obtained experimentally.1 Specifically, it was found that the discrepancy between the experimental and calculated PN stretching frequency of F2P(S)N was less than 35 cm-1, as was the difference between the predicted and measured SN stretching frequencies of F2PSN. Only the SN stretching frequency of the singlet state of F2PNS calculated using CCSD(T) deviated from the experiment by a large amount, with a discrepancy of 155.5 cm-1.1 Moreover, the experiment assigned three absorption bands at λmax = 370, 285, and 240 nm in the Ne-matrix UV-vis spectrum to F2PNS.1 Equation-of-motion CCSD (EOM-CCSD) calculations were performed to reproduce the UV-vis spectrum of F2PNS. Although EOM-CCSD is a highly accurate method,2 it did not reproduce the UV-vis spectrum of F2PNS – in particular, it was found that a band at 370 nm was absent in the EOM-CCSD calculations.1 In summary, there were some inconsistencies between the experimental results and the high-level ab initio calculations in the previous study that require elucidation. In this work, high-level ab initio calculations such as CCSD(T) and secondorder multiconfigurational perturbation theory (CASPT2) are used to find the ground states of the potential energy surface (PES) of F2(P)SN, F2PSN, and F2PNS. We consider both the singlet and triplet states of F2(P)SN, F2PSN, and F2PNS in this work. 3 ACS Paragon Plus Environment


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The calculated results are consistent with the recent experimental observations1 and the inconsistencies are elucidated.

2. Computational Details The molecular structures of the singlet and triplet states of F2(P)SN, F2PNS, and F2PSN were optimized using the CCSD(T) method.3 CCSD(T) based on the restricted Hartree-Fock

(RHF)

reference

wave

function

and

unrestricted

CCSD(T)

(UCCSD(T))4 based on the restricted open-shell Hartree-Fock (ROHF) reference wave function were used for the singlet and triplet states, respectively. Hereafter, we denote both methods as CCSD(T). Subsequent vibrational frequency calculations were also performed to identify the structures at the minimum of PES. The scalar relativistic effects were considered using the second-order Douglas-Kroll-Hess (DKH2) method.5-6 In the CCSD(T) calculations, the aug-cc-pVTZ-DK basis sets7 were used; “DK” indicates that the basis sets were reoptimized to be appropriate for use with the DKH2 method. The 1s orbital of N and F and the 1s, 2s, and 2p orbitals of P and S were not correlated in the CCSD(T) calculations. All CCSD(T) calculations were performed using the Molpro2012 program.8 The complete active space self-consistent field (CASSCF) method9 was used to consider the multireference character and calculate their excitation energies. The 2s and 2p orbitals of N and the 3p orbitals of P and S were selected as the active orbitals for F2(P)SN and F2PNS. Thereby, a total of twelve electrons were distributed across ten active orbitals. Hereafter, this is denoted as CAS(12,10). It is of note that including the 2s orbital of N into the active space was necessary to correctly describe the excited states, especially for F2PNS. The 2s orbital of N was excluded from the active space of F2PSN, therefore CAS(10,9) was used for the CASSCF calculations of F2PSN. The active orbitals of F2P(S)N, F2PNS, and F2PSN are shown in Figures S1, S2, and S3 in the Supporting Information (SI), respectively. To consider the dynamic electron correlation effect, the multi-state CASPT2 (MS-CASPT2) method10 based on the state-average CAS(12,10) reference wave function was used, except for the triplet state of F2PSN, where CASPT211-12 based on the state specific CAS(10,9) wave function was used. Hereafter, both the MS-CASPT2 and CASPT2 methods are denoted as (MS-)CASPT2. The number of correlated electrons in the (MS-)CASPT2 calculations was the same as in the CCSD(T) calculations. The DKH2 method was used to consider the scalar relativistic effect, as in the CCSD(T) calculations. 4 ACS Paragon Plus Environment

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Therefore, the aug-cc-pVTZ-DK basis sets were also used in all (MS-)CASPT2 calculations. The geometry optimizations of both the singlet and triplet states of F2(P)SN, F2PNS, and F2PSN were performed using the (MS-)CASPT2 method without symmetry constraints. The vibrational frequency calculations using MSCASPT2 were performed only for the singlet state of F2PSN. To characterize the excited states of F2(P)SN, F2PNS, and F2PSN, the vertical excitation energies (Tv) of the optimized molecular structures were calculated by MSCASPT2. Improving the basis sets to aug-cc-pVQZ-DK did not alter the excitation energies, and so the aug-cc-pVTZ-DK basis sets were used in all Tv calculations. The 2s orbital of S was included in the active space, meaning that CAS(14,11) was used in all Tv calculations. Six singlet states, seven triplet states, and seven singlet states were averaged in SA-CAS(14,11) calculations for F2P(S)N, F2PNS, and F2PSN, respectively. The active orbitals of F2P(S)N, F2PNS, and F2PSN are shown in Figures S4, S5, and S6 in the SI, respectively. Subsequently, the MS-CASPT2 method was used to examine the dynamic electron correlation effect in the Tv calculations. In all MS-CASPT2 calculations, the Cholesky decomposition of two-electron integrals (threshold of 10-8) was used.13 All MS-CASPT2 calculations were performed using the Molcas8.0 program.14 The anharmonic effect on the vibrational frequencies of the singlet state of F2PSN was examined at the density functional theory (DFT)15-16 level due to computational costs. In the DFT calculations, B3LYP,17-18 B3PW91,18-19 PBE0,20 and APFD21 functionals with the aug-cc-pVTZ basis set were used. We used the “superfinegrid” option to ensure the accuracy of the DFT calculations. All DFT calculations were performed using the Gaussian09 program.22

3. Results and discussion 3.1 Ground state The optimized molecular structures and relative energies of the singlet and triplet states of F2(P)SN, F2PNS, and F2PSN as calculated using CCSD(T) and (MS)CASPT2 with the aug-cc-pVTZ-DK basis sets are shown in Figure 1. It can be seen that the ground state of F2PNS is not a singlet state but a triplet state; the singlet state of F2PNS lies 4.0 kcal/mol higher in energy than the triplet state. In addition, the triplet state of F2PNS is the global minimum for all the isomers. Both the CCSD(T) and (MS-)CASPT2 methods predict the triplet state of F2PNS as the global minimum. 5 ACS Paragon Plus Environment


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This result differs from that seen in the previous study1 because only the singlet state of F2PNS was considered in that work. In contrast, the ground states of F2P(S)N and F2PSN are the singlet states. It is noticeable that (MS-)CASPT2 gives almost the same results as those of CCSD(T), except for the relative energies of the triplet state (3Aʺ) of F2P(S)N. The (MS-)CASPT2 method slightly underestimates the relative energy of the 3Aʺ state of F2P(S)N compared with that predicted by CCSD(T). In addition, all the geometrical parameters of all the states optimized by (MS-)CASPT2 are very close to those predicted using CCSD(T), except for the P−S bond length of the 1A state of F2PSN, as can be seen in Figure 1. These results indicate that (MS-)CASPT2 shows good performance for calculating the molecular properties of this kind of molecule. As shown in Figure 1, the P−S bond length (2.362 Å) of the 1A state of F2PSN as optimized by (MS-)CASPT2 is larger than that predicted by CCSD(T) (2.335 Å). The electronic configuration of the 1A state of F2PSN in the MS-CASPT2 wave function contains 1.5% of an electronic configuration where two electrons occupy the σ* orbital of the P−S bond (see Figure S3 in the SI), leading to the elongation of the P−S bond. The triplet state (3A) of F2PNS is slightly distorted from the Cs structure (see the dihedral angle in Figure 1). The optimized molecular structures of the singlet and triplet states of F2PNS with Cs symmetries show imaginary frequencies in the CCSD(T) calculations at 44.2i and 48.5i cm-1, respectively. The directions of these two vectors break the planes of the Cs symmetries. However, the Cs-symmetric triplet state of F2PNS optimized using CCSD(T)/aug-cc-pVTZ without the DKH2 method shows no imaginary frequency in the minimum energy structure.

3.2 Vibrational frequency The vibrational frequencies of the singlet and triplet states of F2(P)SN, F2PNS, and F2PSN as calculated by CCSD(T)/aug-cc-pVTZ-DK are summarized in Table 1, along with the recent experimental results.1 As can be seen from Table 1, the calculated vibrational frequencies of the singlet state of F2P(S)N are in excellent agreement with the experimental values reported in the previous study. The difference between the calculated and reported P−N stretching frequency of the singlet state of F2P(S)N is less than 10 cm-1. However, as mentioned above, the S−N stretching frequency of the singlet state of F2PNS as calculated by CCSD(T) (1064.6 cm-1) is far from the experimental value (1223.5 cm-1, ref 1), with the discrepancy being 158.9 6 ACS Paragon Plus Environment

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cm-1. The same result was reported in the previous study. As shown in the previous section, the ground state of F2PNS is the triplet state. Therefore, the experimentally observed S−N stretching frequency should correspond to that of the triplet state of F2PNS. Indeed, the S−N stretching frequency calculated by CCSD(T) (1239.2 cm-1) is in excellent agreement with the experimental value (1223.5 cm-1, ref 1). In addition, the other vibrational frequencies of the triplet state of F2PNS are in better agreement with the experimental values than those of the singlet state, with the exception of the PSN bending mode. As shown in Figure 1, both the CCSD(T) and (MS-)CASPT2 methods predict the singlet state of F2PSN as the ground state. Therefore, the vibrational frequencies of the singlet state of F2PSN will correspond to the experimentally observed frequencies. Indeed, with only two exceptions, the calculated vibrational frequencies of the singlet state of F2PSN are in good agreement with the experimental values.1 For example, the S−N stretching frequency calculated by CCSD(T) (1139.7 cm-1) is well matched with the experimental value (1175.5 cm-1, ref 1). However, the P−S stretching (196.6 cm-1) and PSN bending (457.3 cm-1) frequencies of F2PSN calculated by CCSD(T) are far from the experimentally observed frequencies (270.4 and 376.9 cm-1, respectively, ref 1). This discrepancy can be ascribed to the multireference character of the singlet state of F2PSN, because the only structural difference between the MS-CASPT2 and CCSD(T) is the P−S bond length. However, in general, as bond length increases, the vibrational frequency decreases. Indeed, the P−S stretching frequency calculated using MS-CASPT2 (185.1 cm-1) is slightly reduced compared to that predicted by CCSD(T), resulting in further deviation from the experimental value (270.4 cm-1, ref 1). Therefore, consideration of multireference character does not improve the result. In the case of the PSN bending frequency, considering multireference character slightly improves the result. However, it is still far from the experimental value.1 Thus, we also examine the anharmonic effect on the PSN bending frequency using DFT calculations. The harmonic and anharmonic vibrational frequencies of F2PSN calculated by B3LYP, B3PW91, PBE0, and APFD functionals are summarized in Table S1 in the SI. The anharmonic effect on the PSN bending and P−S stretching frequency is not negligible, and varies significantly with the DFT functional used. In general, the anharmonic effect reduces the PSN bending frequency, bringing the calculated frequency closer to the experimental value. The P−S stretching frequency including anharmonic effect is also closer to the 7 ACS Paragon Plus Environment


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experimental value (except the case of APFD functional). However, the difference between the calculated and experimental values still remains. It is noted that both vibrational frequencies that show significant deviations are related to the P−S bond. Thus, it may be that the Ar matrix strongly interacts with the polarizable P and S atoms in F2PSN, resulting in the shift of the two vibrational frequencies. Indeed, the interaction energy between Ar and S atoms is not negligible in the MP2 and CCSD(T) calculations.23

3.3 UV-vis spectrum The Tvs of F2(P)SN, F2PNS, and F2PSN as calculated using MS-CASPT2/aug-ccpVTZ-DK are listed in Table 2. The previous experimental study suggested that the three broad absorption bands at λmax = 370, 285, and 240 nm corresponded to F2PNS.1 Because the ground state of F2PNS is not the singlet state but the triplet state, the previous EOM-CCSD calculations performed on the singlet state of F2PNS could not reproduce the band at 370 nm. We performed Tv calculations on the triplet state of F2PNS, and the calculated UV-vis spectrum of F2PNS is shown in Figure S7 in the SI. The calculated UV-vis spectrum clearly shows a broad absorption band at 370 nm that was not predicted in the previous EOM-CCSD calculations.1 The calculated UV-vis spectrum does not show the absorption band at 285 nm. This is ascribed to the generation of the spectrum by overlapping Gaussian functions. As shown in Table 2, the absorptions of F2PNS near 285 nm exist as the 5th and 6th triplet electronic states of F2PNS, although MS-CASPT2 slightly overestimates the absorption energy compared with the experimental values. It is noted that the MS-CASPT2 results show two absorption peaks (365 and 341 nm, see Table 2) that make up the broad absorption band at 370 nm. In addition, the oscillator strengths of these two peaks are similar to each other. Therefore, irradiation at 365 nm populates these two excited states simultaneously, allowing two distinct photochemical reactions to occur from the two excited states. Indeed, irradiation of F2PNS at 365 nm was shown to generate F2(P)SN and F2PSN in the recent experiment.1 Our calculated results strongly support these experimental observations. The previous experimental study also observed F2P(S)N and F2PSN absorption bands at 275 and 310 nm, respectively.1 As can be seen in Figure S7 in the SI, the calculated UV-vis spectrum of F2P(S)N shows a broad absorption band whose


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λmax is close to 275 nm that corresponds to the 5th singlet excited state (258 nm) of F2P(S)N (see Table 2). As is the case for F2PNS, the MS-CASPT2 slightly overestimates the absorption energy, but this may be due to the existence of the Ne matrix. Irradiation at >495 nm led to the isomerization from F2P(S)N to F2PNS. According to the calculated results, the first excited state of F2P(S)N (615 nm) participates in this photoisomerization. As can be seen from Table 2 and Figure S7 in the SI, both the 4th and 5th excited states of F2PSN correspond to the experimentally observed absorption band at 310 nm. In the previous experimental study, irradiation at 330 nm was found to isomerize F2PSN to F2PNS. According to the results calculated by MS-CASPT2, the 4th singlet excited state participates in this photoisomerization. If higher energy excitation is possible, both the 4th and 5th excited states are populated simultaneously, as in the case of F2PNS, allowing distinct photochemical reactions to take place. In summary, the MS-CASPT2 method reproduces the UV-vis absorption spectrum well, and the experimental observations1 are clearly elucidated.

4. Conclusions High-level ab initio calculations were performed to elucidate the inconsistencies between recent experimental results and quantum chemical calculations. The calculated results show that the ground state of F2PNS is found not to be a singlet state but instead a triplet state. In the previous study, the lack of consideration of the triplet state of F2PNS resulted in the inconsistencies between the experimental and calculated results. The triplet state of F2PNS is the global minimum of the isomers. The vibrational frequencies of the triplet state of F2PNS are better matched with the experimental values. The Tv calculations of the triplet state of F2PNS clearly resolve the experimentally observed absorption bands. The results of the Tv calculations of F2P(S)N and F2PSN by MS-CASPT2 reproduce the experimental results well. Therefore, all calculated results in this work are consistent with the recent experimental observations.

ASSOCIATED CONTENTS Supporting Information



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The Supporting Information is available free of charge on the ACS Publications website at DOI: Active orbitals of CAS(12,10) for F2P(S)N (Figure S1) and F2PNS (Figure S2), active orbitals of CAS(10,9) for F2PSN (Figure S3), active orbitals of CAS(14,11) for F2P(S)N (Figure S4), F2PNS (Figure S5), and F2PSN (Figure S6), calculated UV-vis spectrum (Figure S7), and the harmonic and anharmonic vibrational frequencies of the singlet state of F2PSN calculated using DFT methods (Table S1).

AUTHOR INFORMATION Corresponding Author *E-mail: [email protected]. Tel: +82-2-2164-4338. Fax: +82-2-2164-4764.

ACKNOWLEDGMENTS This work was supported by the Catholic University of Korea, Research Fund, 2016. This research was also supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning (NRF-2014R1A1A1007188). This work was also supported by the National Institute of Supercomputing and Network/Korea Institute of Science and Technology Information with supercomputing resources including technical support (KSC-2016-C1-0002).

REFERENCES (1) Li, H.; Wu, Z.; Li, D.; Zeng, X.; Beckers, H.; Francisco, J. S., A Singlet Thiophosphoryl Nitrene and Its Interconversion with Thiazyl and Thionitroso Isomers. J. Am. Chem. Soc. 2015, 137, 10942-10945. (2) Jensen, F., Introduction to computational chemistry. John Wiley & Sons, West Sussex PO19 8SA, England, 2013. (3) Hampel, C.; Peterson, K. A.; Werner, H.-J., A comparison of the efficiency and accuracy of the quadratic configuration interaction (QCISD), coupled cluster (CCSD), and Brueckner coupled cluster (BCCD) methods. Chem. Phys. Lett. 1992, 190, 1-12.


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(4) Watts, J. D.; Gauss, J.; Bartlett, R. J., Coupled- cluster methods with noniterative triple excitations for restricted open- shell Hartree–Fock and other general single determinant reference functions. Energies and analytical gradients. J. Chem. Phys. 1993, 98, 8718-8733. (5) Hess, B. A., Relativistic electronic-structure calculations employing a twocomponent no-pair formalism with external-field projection operators. Phys. Rev. A 1986, 33, 3742-3748. (6) Jansen, G.; Heß, B. A., Revision of the Douglas-Kroll transformation. Phys. Rev. A 1989, 39, 6016-6017. (7) De Jong, W. A.; Harrison, R. J.; Dixon, D. A., Parallel Douglas–Kroll energy and gradients in NWChem: estimating scalar relativistic effects using Douglas–Kroll contracted basis sets. J. Chem. Phys. 2001, 114, 48-53. (8) Werner, H.-J.; Knowles, P. J.; Knizia, G.; Manby, F. R.; Schütz, M.; Celani, P.; Korona, T.; Lindh, R.; Mitrushenkov, A.; Rauhut, G.; et al. MOLPRO, version 2012.1, a package of ab initio programs, 2012. http://www.molpro.net (accessed June 18, 2014). (9) Roos, B., Advances in chemical physics; ab initio methods in quantum chemistry II. Wiley, Chichester, 1987. (10) Finley, J.; Malmqvist, P.-Å.; Roos, B. O.; Serrano-Andrés, L., The multi-state CASPT2 method. Chem. Phys. Lett. 1998, 288, 299-306. (11) Andersson, K.; Malmqvist, P. A.; Roos, B. O.; Sadlej, A. J.; Wolinski, K., Second-order perturbation theory with a CASSCF reference function. J. Phys. Chem. 1990, 94, 5483-5488. (12) Andersson, K.; Malmqvist, P. Å.; Roos, B. O., Second- order perturbation theory with a complete active space self- consistent field reference function. J. Chem. Phys 1992, 96, 1218-1226. (13) Aquilante, F.; Boman, L.; Boström, J.; Koch, H.; Lindh, R.; de Merás, A. S.; Pedersen, T. B., Cholesky decomposition techniques in electronic structure theory. In Linear-Scaling Techniques in Computational Chemistry and Physics, Springer: 2011; pp 301-343. (14) Aquilante, F.; Autschbach, J.; Carlson, R. K.; Chibotaru, L. F.; Delcey, M. G.; De Vico, L.; Ferré, N.; Frutos, L. M.; Gagliardi, L.; Garavelli, M., Molcas 8: new capabilities for multiconfigurational quantum chemical calculations across the periodic table. J. Comput. Chem. 2016, 37, 506-541. 11 ACS Paragon Plus Environment


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(15) Hohenberg, P.; Kohn, W., Inhomogeneous Electron Gas. Phys. Rev. B 1964, 136, 864-871. (16) Kohn, W.; Sham, L. J., Self-Consistent Equations Including Exchange and Correlation Effects. Phys. Rev. A 1965, 140, 1133-1138. (17) Lee, C.; Yang, W.; Parr, R. G., Development of the Colle-Salvetti correlationenergy formula into a functional of the electron density. Phys. Rev. B 1988, 37, 785789. (18) Becke, A. D., Density- functional thermochemistry. III. The role of exact exchange. J. Chem. Phys. 1993, 98, 5648-5652. (19) Perdew, J. P.; Wang, Y., Accurate and simple analytic representation of the electron-gas correlation energy. Phys. Rev. B 1992, 45, 13244-13249. (20) Adamo, C.; Barone, V., Toward reliable density functional methods without adjustable parameters: The PBE0 model. J. Chem. Phys. 1999, 110, 6158-6170. (21) Austin, A.; Petersson, G. A.; Frisch, M. J.; Dobek, F. J.; Scalmani, G.; Throssell, K., A density functional with spherical atom dispersion terms. J. Chem. Theory Comput. 2012, 8, 4989-5007. (22) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; et al. Gaussian 09, revision D.01; Gaussian, Inc.: Wallingford, CT, 2009. (23) Borocci, S.; Bronzolino, N.; Grandinetti, F., Noble gas–sulfur anions: a theoretical investigation of FNgS−(Ng= He, Ar, Kr, Xe). Chem. Phys. Lett. 2008, 458, 48-53.


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Table 1. Vibrational frequencies (in cm-1) of F2P(S)N, F2PNS, and F2PSN calculated by CCSD(T)/aug-cc-pVTZ-DK.

F2P(S)N

F2PNS

F2PSNb

Singlet 172.3 280.5 318.3 393.3 407.0 624.4 865.9 924.5 1180.2 48.3 168.5 312.7 356.4 422.7 612.0 839.3 858.3 1064.6 22.2 [10.6] 95.6 [79.6] 190.0 [177.0] 196.6 [185.1] 356.8 [353.4] 457.3 [452.2] 825.8 [823.7] 831.0 [828.8] 1139.7 [1143.0]

Triplet 241.8 195.3 309.4 349.6 383.8 655.1 780.7 913.9 943.0 32.6 178.6 302.4 311.5 423.4 658.8 833.8 851.4 1239.2 47.2 144.4 237.9 257.7 383.9 479.8 842.2 851.4 789.5

Exp.a 331.9 405.6 418.5 631.4 873.2 925.5 1189.6 309.4 323.6 430.7 626.7 825.6 842.9 1223.5 270.4 358.9 376.9 817.8 845.8 1175.5

Vibration Mode PF2 rocking NS Stretch. PS stretch. PF2 wagging PF2 scissoring PSN bend. PF2 sym. Stretch. PF2 asym. stretch. PN stretch PF2 rocking PF2 wagging PF2 scissoring PF2 twisting PN stretch. PSN bend. PF2 asym. stretch. PF2 sym. stretch. SN stretch. PF2 rocking PF2 wagging PF2 twisting PS stretch. PF2 scissoring PSN bend. PF2 asym. stretch. PF2 sym. stretch. SN stretch.

a: Observed in Ar matrix, ref 1 b: Values in square brackets are calculated by MS-CASPT2/aug-cc-pVTZ-DK.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48

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Table 2. Tvs (in nm) of F2P(S)N, F2PSN, and F2PNS calculated by MS-CASPT2/aug-cc-pVTZ-DK. Values in parentheses are oscillator strengths. F2PNS

Electronic configurationa

F2P(S)N

Electronic configurationb

F2PSN

Electronic configurationc

1

0

0

|2222220000> 89.3%

0

|22222220000> 87.8%

2

365 (0.036)

615 (0.000)

|22222αβ000> 89.2%

1201 (0.000)

|222222αβ000> 87.1%

3

341 (0.031)

|222222αα000> 91.1% |2222α22α000> 71.1% |2222α2α2000> 12.4% |222α222α000> 6.6% |2222α2α2000> 61.2% |22222αα2000> 14.4% |2222α22α000> 7.6% |222α22α2000> 5.3%

274 (0.003)

|2222αβ2000> 17.3% |22α222β000> 69.3% |222α2β2000> 5.8%

418 (0.004)

|22222202000> 84.3%

4

298 (0.008)

|22222α2α000> 74.2% |22222αα2000> 11.9%

271 (0.000)

|2222202000> 84.5% |2202222000> 9.0%

323 (0.052)

5

262 (0.046)

|222α222α000> 60.1% |22222αα2000> 26.7%

258 (0.013)

|222α22β000> 84.0%

299 (0.074)

6

243 (0.049)

253 (0.002)

|22222α0β00> 83.1%

252 (0.002)

|22222α2β000> 68.2% |222α222β000> 19.7%

7

234 (0.161)

-

252 (0.002)

|222α222β000> 28.5% |2222α2β2000> 26.6% |2222220αβ00> 15.9% |22222α2β000> 11.3%

|222α22α2000> 53.0% |22222αα2000> 21.7% |222α222α000> 9.2% |222α22α2000> 30.7% |22222αα2000> 15.9% |2222α2α2000> 15.2% |22222α2α000> 10.7% |222α222α000> 9.0%

-

a: The order of molecular orbitals is the same as that in Figure S5 in the SI. b: The order of molecular orbitals is the same as that in Figure S4 in the SI. c: The order of molecular orbitals is the same as that in Figure S6 in the SI.


|222222α0β00> 32.3% |2222220αβ00> 27.3% |222α222β000> 7.7% |222222α0β00> 37.6% |2222220αβ00> 22.9% |222α222β000> 7.8%

Page 15 of 16

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48


Figure 1. Optimized molecular structures (bond lengths in Å and bond angles in °) and relative energies (in kcal/mol) of the singlet and triplet states of F2P(S)N, F2PNS, and F2PSN using CCSD(T) (electronic energy in plain and zero-point corrected energy in bold) and (MS-)CASPT2 (geometrical parameters in parentheses and electronic energy in italics) with aug-cc-pVTZ-DK.



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Table of Contents (TOC)


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P(S) - ACS Publications - American Chemical Society

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