J. Phys. Chem. 1986, 90, 575-579 are split by the Jahn-Teller distortion. The separation between the peak and shoulder is about 750 cm-' and is of a comparable order of magnitude to the splitting of Q, and Q,, in the solution electronic spectra from soluble phthalocyanines (Figure 1). The actual energies of the peak and shoulder correspond to a peak and shoulder of the CuPc electronic spectrum. The observation of both origins of the Q band in a resonance profile is unusual in porphyrin systems and is probably due to the allowed nature of the transitions in phthalocyanines. The splitting of 750 cm-' suggests that 0-0 scattering would be more intense than 0-1 scattering. 0-1 scattering from Q, at about 700 nm cannot be. discerned, but from Qy,the higher-energy vibrations give rise to a 0-1 peak in the profiles which, with the exception of u28 (1450 cm-I), is weaker than the 0-0 peak. The separation between the two peaks indicated in Figure 5 is between 15 and 25% less than the corresponding ground state vibrational frequency due both to reduced force constants in the excited state and to constructive interferences which with A term enhancement reduces the separation between the peaks.24 For low-frequency vibrations, the 0-1 peaks are not clearly resolved but the profiles are skewed in different ways consistent with the existence of some 0-1 intensity. A consequence of Shelnutt et al.'s analysis is that B,, and B2, but not A2, vibrations may have A term enhancement. Although both A and B term enhancement may contribute to the intensity, the prominence of A,, vibrations and the fact that B,, and BZg vibrations, but not A, vibrations, are intense suggests that A term enhancement predominates. Further, a t the disk concentration used for these profiles, the spectrum at 488 nm is very weak and, consequently, the increase in intensity with decreasing wavelength in profiles such as u3 and uZ8indicates that there is further structure in the region between 580 and 514 nm. This suggests possible strong 0-2 scattering, again indicative of A term involvement. The u3 profile has subsidiary maxima corresponding to a quantum of u7 added to both the 0-0 and 0 - 1 peaks. These appear to be helper modes and one quantum of u3 appears to be present (24) Clark, R. J. H.; Dines, T. R. Mol. Phys. 1981, 42, 193.
575
in the u7 profile. The helper modes are much more intense at room temperature and, with u3 profile, the second one corresponding to u3 + u7 above the 0-0 transition is the largest peak at room temperature. Another notable feature is that the main peak in the low-frequency profiles is weaker but sharper at room temperature. These two changes with temperature are further evidence that the molecule is held in a much more defined environment at 10 K with lower vibrational amplitudes and less possibility of sufficient freedom for multimode interactions. Thus, resonance Raman scattering from a-CuPc in the Q band region has similarities to the equivalent porphyrin systems largely because the electronic transitions concern the inner ring system. Compared to porphyrin systems, there is a larger A term contribution and both electronic origins can be identified and hence assigned in the electronic spectrum. Although the vibronic intensities measured in electronic spectroscopy are different from those obtained by Raman, the size of the Jahn-Teller splitting of the electronic origins can be used to compare the electronic spectrum with calculations of band shapes. The spectrum is in reasonable agreement with previous calculations.25 Finally, this analysis has demonstrated that a metal disk has significant advantages as a method for the measurement of resonance Raman profiles of materials in the solid state. It can increase the ratio of scattered to absorbed radiation, alter or quench fluorescence, and provide a suitable matrix for temperature-dependent or low-temperature studies. The advantage of low-temperature studies is illustrated by the use made of the resolution of the solid-state a-CuPc profile at 10 K to compare with solution porphyrin profiles.
Acknowledgment. We thank the SERC and Ciba/Geigy PLC for the award of a CASE studentship (A.J.B.), the Royal Society for a grant in aid to purchase the Displex equipment, and Drs. I. A. Macpherson andrC. D. Campbell of Ciba/Geigy for advice and encouragement throughout. Registry No. a-CuPc, 147-14-8. (25) Bersuker, I. B. Coord. Chem. Reu. 1975, 14, 375.
Infrared Spectrum of a Symmetrical Phosphine-Ozone Complex in Solid Argon Robert Withnall, Michael Hawkins, and Lester Andrews* Chemistry Department, University of Virginia, Charlottesville, Virginia 22901 (Received: July 1 , 1985)
Cocondensation of Ar/PH3 and Ar/03 samples at 12-18 K has produced sharp satellite absorptions at 1037.3 cm-l below u3 of O3 at 1039.9 cm-I, at 988.5 and 986.3 cm-l below u2 of PH3 at 994 cm-I, and at 705.2 cm-' above u2 of O3at 7 0 4 . 4 cm-I. These bands, which photolyzed with red visible light and were reproduced on sample warming to allow reagent diffusion, are assigned to the PH3-03 complex. A sharp sextet in 16,1803 experiments indicated a symmetrical attachment of ozone in the complex. The red visible photolysis is postulated to involve a charge-transfer mechanism.
Introduction Ozone complexes have played an important role in the photochemistry of ozone-reactive molecule matrix systems in a large number of recent studies. These complexes have been characterized by modification of the ozone photochemistry in the case by displacements of ClF, SO2,ICl, CH31, and CF31 of vibrational modes of the submolecules in the case of CIF, ICl, CH31, CF31, C2H4, H 2 0 , and NH3 complexes,'-7 and by the ( 1 ) Andrews, L.; Chi, F. K.; Arkell, A. J . Am. Chem. Soc. 1974,96, 1997. (2) Kugel, R.; Taube, H. J . Phys. Chem. 1975, 79, 2130. (3) Hawkins, M.; Andrews, L.; Downs, A. J.; Drury, D. J. J . Am. Chem. SOC.1984, 106, 3076. (4) Hawkins, M.; Andrews, L . Inorg. Chem., 1985, 24, 3285.
0022-3654/86/2090-0575$01.50/0
appearance of new photolysis products in the case of the former complexesl-5 and in ozone complexes with PF3,AsF3, C2H4,and SiH4.*-I0 Of particular interest here are the ICl, CH31, and CF31complexes with ozone, which photolyze with high cross section in the visible region to give new product species involving a postulated charge-transfer m e c h a n i ~ m . ~ -Here ~ follows a study of the (5) Andrews, L.; Hawkins, M.; Withnall, R. Inorg. Chem., to be published. (6) Frei, H.; Fredin, L.; Pimentel, G. C. J . Chem. Phys. 1981, 74, 397. (7) Nord, L. J. Mol. Srrucr. 1982, 96, 37. (8) Downs, A. J.; Gaskill, G. P.; Saville, S. B. Inorg. Chem. 1982, 21, 3385. (9) Hawkins, M.; Andrews, L. J . Am. Chem. SOC.1983, 105, 2523. (10) Withnall, R.; Andrews, L. J . Am. Chem. SOC.1985, 107, 2567; J . Phys. Chem. 1985, 89, 3261.
0 1986 American Chemical Society
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Withnall et al.
The Journal of Physical Chemistry, Vol. 90, No. 4, 1986
I' m N
N N
WCO
u . ZU
m
U
E o m '
I
a-
3-
".
N l I050
1045 1040 1035 WAVENUMBERS
1030
, 1
1000
I
99s
1
990 9Qs WflVENUMBERS
I
9ao
!1710
WAVENUMBERS L
5
Figure 1. Infrared spectra in the 695-710-, 980-1000-, and 1030-1050-~m-~regions of Ar/PH3 = 300/1 and Ar/03 = 300/1 samples: (a) after codeposition of 30 mmol of each sample at 16 K, (b) after 590-1000-nm photolysis for 20 min, (c) after 515-1000-nm photolysis for 20 min. Note different absorbance scales.
phosphine-ozone complex in solid argon using infrared spectroscopy as part of our continuing investigation of the chargetransfer interaction of ozone and the photochemistry of its complexes. Experimental Section
Apparatus. The cryogenic refrigeration systems operating at 12-1 8 K and the vacuum vessels have been described previously." Infrared spectra of samples were recorded on a Nicolet 7 199 FTIR spectrometer at 0.24-cm-I resolution in the 4000-400-~m-~range. The temperature of the CsI cold window was determined by a CTI Cryogenics temperature indicator/controller using an Au-Co vs. Cu thermocouple. Samples were irradiated for 20-min intervals with a BH-6 high-pressure mercury arc lamp (1000 W, Illumination Industries Inc.) in combination with 10-cm water and Coming glass filters, which exposed the samples to either 590-1000 nm (A) or 515-1000 nm (B) wavelength ranges. Chemicals. Ozone was generated by a static electric discharge (Tesla coil) of oxygen in a Pyrex tube and condensed with liquid N2. Residual O2was removed by pumping at 77 K.'* Normal isotopic 0, was obtained from Burdett, U.S.P. grade. Two samples enriched in '*O to 50% and 95%, respectively, were supplied by Yeda (Israel). PH, was supplied by Matheson (C.P. Grade); PD3 and mixtures of PH,, PH,D, PHD,, and PD, were prepared by the reaction of calcium phosphide with D 2 0 and mixtures of D,O and H20, respectively, in a Pyrex bulb attached to the sample manifold. Volatile impurities were removed from all samples by pumping at 77 K. Procedure. Ozone and phosphine were diluted with argon and codeposited through two separate spray-on lines at equal rates of 1.5 mmol h-I for 20 h. A matrix ratio of either 200/1 or 300/1 (11) Kelsall, B. J.; Andrews, L. J . Phys. Chem. 1981, 85, 1288. (12) Andrews, L.; Spiker, Jr., R. C. J . Phys. Chem. 1972, 76, 3208
TABLE I: Infrared Absorptions of Phosphine Isotopes in Solid Argon
PH,
PH,D
PHD,
PD?
u2(a1) de)
2340 994 2345
a 895
1698 729 1705
v4(e)
1114
a 768 1705b 1698 919b 914
ul(al)
a 1701 1097b 97 1
804
"Not resolved from PH3 or PD3. b T ~ bands o observed for lifted degeneracy in mixed isotopic molecules. was used for both the A r / 0 3 and Ar/PH, gas mixtures. The samples were irradiated after deposition. Results
The argon matrix infrared spectra of PH3 and PD, have been previously reported.I3 Spectra of Ar/(PH,, PH2D, PHD2, and PDJ = 200/1 with varying relative concentrations of PH3, PH,D, PHD2, and PD3 were compared to the argon matrix infrared spectra of PH3and PD3 and to gas-phase spectra of PH3, PH2D, PHD,, and PD,.14,15 The argon matrix absorptions for PH,, PH2D, PHD,, and PD3 are listed in Table I; agreement with gas-phase assignments for the mixed isotopes is good where both gas-phase and matrix values have been observed. 1603 + PH3. Codeposition of mixtures of Ar/PH3 = 30011 and Ar/03= 300/ 1 at temperatures ranging from 12 to 18 K revealed new satellite absorptions: a strong sharp band at 1037.3 cm-' below the Y,(Oj) fundamental at 1039.9 cm-', two strong, sharp bands at 988.5 and 986.3 cm-I below the PH, symmetric defor(13) Arlinghaus, R. T.; Andrews, L. J. Chem. Phys. 1984, 81, 4341. (14) Lee, E.; Wu, C. K. Trans. Faraday SOC.1939, 35, 1366. McConaghie, V. M.; hielsen, H. H. J . Chem. Phys. 1953, 21, 1836. (1 5) Weston, Jr., R. E.; Sirvetz, M. H. J . Chem. Phys. 1992, 20, 1820.
The Journal of Physical Chemistry, Vol. 90, No. 4 , 1986 577
Phosphine-Ozone Complex in Solid Argon
TABLE II: New Absorotions due to IsotoDic PhosDhine-Ozone Complexes in Solid Areona ~~~~~
~
isotopic ozone 16-16-16 1102.4 (2.0) 1037.2 (2.7) 705.2(-0.8)
u,(ozone) v,(ozone) u2(ozone)
16-18-16 1003.9 (2.6) 697.3 (-0.8)
18-16-16 1089.1 (1.1) 1023.4 (2.8) 688.8(-0.8)
18-16-18
18-18-16 1060.2 (1.6) 989.4 (2.6) 681.5 (-0.7)
1014.5 (2.6) 672.3 (-0.8)
18-18-18 1041.2 (1.5) 980.3 (2.5) 665.4 (-0.7)
isotouic uhosuhine u,(phos) Y2(PhOS) udphos)
PH,
PHID
PHDz
PD3
988.5(5.5) 986.3 (7.7)
890.0(4.6) 888.1 (6.5) 967.3 (3.4)
765.2 (3.0) 763.8 (4.4) 910.1 (3.8)
726.1 (2.9) 724.3 (4.7)
"Numbers in parentheses indicate the frequency shift of the submolecule fundamental in the complex relative to its value in the isolated molecule; positive values indicate red shifts and negative values indicate blue shifts. Frequency accuracy is fO.l cm-'. mation at 994 cm-I, and a weaker band at 705.2 cm-I on the high-frequency side of the O3 bending mode at 704.4 cm-I, are labeled C in Figure la. A weak new band (not shown) was also observed at 1102.4 cm-I below the v1 fundamental of ozone at 1104.4 cm-'. Irradiation A reduced these bands in intensity by approximately 50%, and they were virtually destroyed by irradiation B, as shown in Figure 1, b and c. The loss of the above new absorptions upon irradiations A and B was accompanied by the appearance of a large number of product absorptions, which will be discussed in detail in a following article.I6 It is noteworthy that photoproduct absorptions were observed in the initial scan of the deposited sample with 7% of the yield produced by irradiation A, which could arise from 632.8-nm reference laser photolysis. Finally, the bands at 1037.3, 705.2, 988.5, and 986.3 cm-I reappeared when the matrix was warmed to 30 K for 10 min and recooled to 12 K. I8O3 PH,. N o I8O shift was observed for the phosphine satellite bands at 988.5 and 986.3 cm-'. The satellite band at 1037.3 cm-I on the low-frequency side of the antisymmetric stretch In addition of I6O3,however, was shifted to 980.3 cm-' with 1803. the band at 705.2 cm-' on the high-frequency side of the I6O3band was shifted to 665.4 cm-' with I8O3,and the band at 1102.4 cm-' was shifted to 1041.2 cm-I. 16,1803 (50% l80) PH3. The ozone satellite band at 1037.3 cm-I gave way to the six absorptions at 1037.3, 1023.4, 1014.5, 1003.9, 989.4, and 980.3 cm-I noted with arrows in Figure 2 with a relative intensity ratio of 1:2:1:1:2:1 and each component redshifted 2.5-2.8 cm-' from a component of the sextet of isolated 16J803. The band at 705.2 cm-I gave way to six absorptions at 705.2, 697.3, 688.8, 681.5, 672.3, and 665.4 cm-I with a relative intensity ratio of 1:1:2:2:1:1 and each component blue-shifted 0.7-0.8 cm-I from a component of isolated 16,1803. O3 PD3. The phosphine satellite at 988.5 and 986.3 cm-I shifted to 726.1 (H/D = 1.361) and 724.3 cm-' ( H / D = 1.362), respectively, with PD,; the H / D ratio for phosphine is 1.386. With scrambled I6J8O3,sextets were observed in the v2 and v3 regions of O3 which had components with the same relative intensities and frequency locations as those observed in the Ar/PH3/16,1803 experiments described above. O3 PH3/PH2D/PHD2/PD3.Mixtures of PH3/PH2D/ PHD2/PD3 in varying relative concentrations were diluted in argon Ar/PH,D3, (x = 0, 1, 2, 3) = 200/1 and codeposited with Ar/I6O3 = 200/1. Figure 3a shows the 700-1000-cm-' region of a PH3-rich mixture of scrambled phosphines (PH3/PH2D/ PHD2 = 7/6/1 estimated by comparing relative intensities of the v(P=O) stretch of phosphine oxide photo products); Figure 3b shows the same spectral region of a PD3-rich mixture of scrambled phosphines (PH2D/PHD2/PD3= 1/8/18). The darkened bands in parts a and b of Figure 3 were destroyed following irradiations A and B, and these bands are collected in Table 11. Product absorptions appearing with irradiations A and B are not shown in Figure 3a,b; they will be discussed in the following article. O3 NH,. Parallel experiments were done with ozone and ammonia. Strong new bands were observed at 986 cm-l in the
+
+
+
+
+
(16)Withnall, R.;Andrews, L., to be published.
:: m
m
W N U Z N.
m
2. L9 N
11050
ld+D
lb30
1020 lblo 1000 WFIVENUMBERS
490
480
970
Figure 2. Infrared spectrum in the 970-1050-cm-' region for Ar/PH3 = 300/1 and Ar/1611803= 200/1 (50% I8O enriched) samples deposited at 16 K. The phosphine submolecule absorptions are labeled C and the ozone submolecule absorptions in the product complex are noted with arrows.
v2 region of ammonia and at 1047 cm-I in the u3 region of ozone. These bands decreased slightly upon irradiation at 380-1000 nm, decreased 25% by 290-1000 nm photolysis and 70% by full-arc experiment gave the 220-1 000-nm irradiation. A similar 1803 same 986-cm-I band and a new 990-cm-' band in the u3 region of leg3.
Discussion The new absorptions will be identified, and the structure and photochemistry of the product complex will be considered. Identification. The new absorptions listed in Table I1 produced by codeposition of PH3 and O3 require both reagents and are assigned to a phosphine-ozone complex. These assignments are supported by the observation that, having destroyed the bands with irradiations A and B, they are reproduced by warming to 30 K for 10 min to allow PH3and O3to diffuse through the matrix and re-form the complex. Furthermore the complex seems to contain one PH3 and one O3molecule, since none of the observed photolysis products contained more than three hydrogen or three oxygen atoms; no evidence was found for phosphine-ozone complexes with any other stoichiometry. The small shifts with respect to the free molecules suggest a weak interaction in which the PH3 and O3 molecules retain their individuality. The 1047- and 986-cm-' bands in ammonia-ozone experiments are likewise assigned to the NH3-03 complex. That they are due to perturbed 0, and N H 3 modes, respectively, is demonstrated by 1803 substitution. These assignments to the NH3-03 complex in solid argon compare favorably with the natural isotopic spectrum in solid nitrogen,17which sustains similar blue shifts for each mode on complexation. Structure and Bonding. Moreover, the sextet of isolated, scrambled 16*1803 in the V 3 ( 0 3 ) antisymmetric stretching region has a satellite sextet belonging to the complex with the same (17) Nard, L. J . Mol. Struct. 1982, 96, 37.
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Withnall et al.
The Journal of Physical Chemistry, Vol. 90, No. 4, 1986
0
ii
m
m
m
0
0 Q
1
0
0
a.
Q
N
~'1000
980
960
Sit0
620
900
880
&SO 890 WRVENUMBERS
620
800
i80
?SO
j90
j20
300
Figure 3. Infrared spectra in the 700-1000-cm-' region for Ar/PH,D,, (x = 0, 1, 2, 3) = 200/1 samples deposited with Ar/0, = 200/1 at 12 K: (a) PH3/PH2D/PHD, = 7/6/1 and (b) PH,D/PHD2/PD3 = 1/8/18. The darkened bands were destroyed by 590-1000- and 515-1000-nm irradiation.
relative intensities of 1:2: 1:1:2:1. Similarly, the sextet of isolated, scrambled in the u 2 ( 0 3 )bending region has a satellite sextet belonging to the complex with the same relative intensities of 1:1:2:2:1:1. The foregoing clearly indicates that the O3submolecule has retained C2, symmetry in the PH3-03 complex, since the relative intensities of the components of the sextet are appropriate for the statistical weights of the isotopes as assigned in Table 11. This stands in marked contrast to the CF31-03 complex where the O3 submolecule loses its C2, symmetry and, with scrambled 16,i803, gives a multiplet with eight components of equal intensity in the V 3 ( 0 3 ) region.' The symmetrical structure for ozone in the PH3-03 complex determined here is in agreement with the structure calculated for the NH3-03 complexis and determined for the (CH3)3N-S02 complex by X-ray crystal10graphy.l~ Interestingly, the ozone submolecule lies on a plane perpendicular to the C3 axis with the apex oxygen atom closest to nitrogen. It is important to contrast the symmetric PH3-03 and asymmetric CF31-03 complexes in view of frontier orbital interactions. The essential difference is that phosphine, like ammonia, has a single lone pair, and this lone pair can overlap favorably with the R* orbital on the apex oxygen in the ozone submolecule. The iodine in CF31,however, has three lone pairs of different symmetry, which interact differently with the three LUMO's of ozone such that the asymmetric arrangement is more stable for the CF31 complex. The ozone valence bond angle of the O3 submolecule in the complex can be calculated directly from the v3 fundamentals of the symmetric O3 isotopes, as has been done for isolated O3.I2 When the four combinations of symmetrical isotopes 16-1816/16-16-16, 18- 16-18/ 18- 18-18, 18-16-18/ 16-16-16, and 161 6 3 1 8 0 3
(18) Lucchese, R. R.; Haber, K.; Schaeffer, 111, H. F. J . Am. Chem. SOC. 1976, 98, 7611. (19) v. d. Helm, D.; Childs, J. D.; Christian, S . D. J. Chem. SOC., Chem. Commun. 1969, 887.
18-16/18-18-18 are used, the u3 assignments listed in Table I1 produce the ozone valence angle cosines -0.3255, -0.3144, -0.5557, and -0.5667, respectively. These cosine values place the ozone valence angle lower limit at 108.7 f 0.4' and the upper limit at 124.1 f 0.4' with an average value of 116.4 f 4'. This value for the valence bond angle of the O3 submolecule in the PH3-03 complex is the same as the bond angle in free O3 in solid argon (1 16.7 f 0.4°)20 within experimental error. The only observed bands belonging to PH, in the complex come a t 986.3 and 988.5 and these are due to the symmetric PH, deformation, red-shifted by 7.7 and 5.5 cm-I, respectively, from the symmetric PH3 deformation of free PH3. The doublet of absorptions observed for this mode in PH3 in the PH3-03 complex is believed to arise from a site-splitting of the matrix. The doublet of absorptions at 724.3 and 726.1 cm-' observed in PD3/03 experiments likewise belongs to the symmetric deformation of PD3 in the complex. For PH2D and PHD2, which are both of C, symmetry, the symmetric deformation modes of PH2D and PHDz give split bands in their ozone complexes that are analogous to those observed for PH3 and PD, as can be seen in Table 11. However, one of the components of the antisymmetric deformation mode is observed for each mixed isotopic complex even though this mode was not resolved from precursor for the PH, and PD, complexes. The complex is believed to form due to a frontier orbital interaction between the phosphine lone pair and the unoccupied R* ozone molecular orbital. Charge transfer to ozone is minimal since the decrease in ul and v3 for ozone in the complex is only 2.0 and 2.7 cm-I and the ozone valence angle is unchanged. This markedly contrasts the Na+03- species where u1 and v3 decrease by 93 and 232 cm-l, respectively, and the valence angle decreases to 11 1 f 30.2' (20) Green, D. W.;Ervin, K.M. J . Mol. Spectrosc. 1981, 88, 51. (21) Spiker, Jr., R. C.; Andrews, L. J . Chem. Phys. 1973,59, 1851, 1863.
Phosphine-Ozone Complex in Solid Argon The present phosphine-ozone complex may be contrasted with phosphite ozonide compounds, which can be prepared by straightforward solution ozonolysis methods.22 The latter compounds decompose to give phosphate esters and singlet molecular oxygenz3with an increase of the valence of phosphorus from three to five; this parallels the photolysis of the PH3-03 complex where phosphorus again increases its valence to five in forming the H3P=0 primary product.16 Another interesting comparison may be made to the H F complexes24-zswith N H 3 and PH3. On the basis of the v2cmode for the base submolecule, NH3-HF (1093 cm-'), NH3-03 (986 cm-l), and isolated N H 3 (979, 956 cm-' inversion doublet),26the HF complex with ammonia is much stronger than the O3 complex. However, the O3 and HF complexes with PH3 result in almost identical 986-cm values for v2c, which is red-shifted 6 cm-I from the free PH3 value whereas the v; modes for the ammonia complexes are substantially blue-shifted from the free N H 3 value, which is split by inversion doubling in solid argon. Charge-Transfer Photochemistry. Charge-transfer excitation of electron donor-acceptor complexes has been studied recently by using time-resolved picosecond spectro~copy.~'In particular the role of ion pairs in the photochemistry of anthracene complexes with tetracyanoethylene and tetranitromethane have been add r e s ~ e d . ~ *The * ~ ~ready photodissociation of the PH3-03complex by irradiation with red mercury arc light using conditions that do not photolyze isolated ozone, the ease of decomposition of 03-, and the extensive 0-atom addition photochemistry strongly suggest that the PH3-03 complex dissociates by a charge-transfer mechanism producing the PH3+-03- ion pair, which easily transfers 0- to give the photolysis products. An estimate of the energy threshold for the light radiation needed to effect charge transfer can be obtained from the relationship
E=I-A+C (1) where Z = adiabatic ionization energy of the PH3 donor, A = electron affinity of the O3acceptor, and C = electrostatic potential (22) Kosolopoff, G. M. 'Organophosphorus Compounds"; Wiley: New York, 1950. (23) Stephenson, L. M.; McClure, D. E. J. Am. Chem. Sot. 1973, 95, 3074. (24) Johnson, G. L.; Andrews, L. J . Am. Chem. SOC.1982, 204, 3043. (25) Arlinghaus, R. T.; Andrews, L. J . Chem. Phys. 1984,81, 4341. (26) Cugley, J. A,; Pullin, A. D. E. Spectrochim. Acta, Part A 1973, 29, 1655. (27) Hilinski, E. F.; Masnovi, J. M.; Amatore, C.; Kochi, J. K.; Rentzepis, P. M. J . Am. Chem. SOC.1983. 105. 6167. (28) Hilinski, E. F.; Masnovi, J. M.;Kochi, J. K.; Rentzepis, P. M. J. Am. Chem. SOC.1984, 106, 8071. (29) Masnovi, J. M.; Kochi, J. K.; Hilinski, E. F.; Rentzepis, P. M. J. Am. Chem.'Soc., to be published.
The Journal of Physical Chemistry, Vol. 90, No. 4, 1986 579 energy of the PH3+-O
