J . Phys. Chem. 1984,88, 2414-2418
2414
interactions, it still results from a purely electrostatic consideration of the problem and cannot eliminate completely the simplification made in eq 3, Le., the neglect of the AHDoterm. Evidently, the contribution of nonelectrostatic interactions to the enthalpy of dilution increases as the solution temperature is decreased. In conclusion, it should be noted that another popular polyelectrolyte theory, the infinite line charge theory of Manning,lo shows all deficiencies observed with the cell theory. According to the theory of Manning the limiting law for AHD reads16 d In m
25
d In T
F>
1
(4)
-
eq 4 are presented in Figures 1-5 as dotted lines. It can be seen that agreement between theory and experiment is good for the acid and lithium salt at all temperatures, for the sodium salt the agreement is good at 15, 25, and 40 "C, whereas for the potassium and cesium salts agreement is satisfactory only at 40 O C . For the cesium salt even the sign of AH, is not correctly predicted at 0 OC. It may be noted that in recent meas~rementsl~ of the enthalpy of mixing of alkali-metal poly(styrenesu1fonates) with the corresponding alkali-metal chlorides similar deviations of the experimental values from predictions of the line charge theory have been observed, increasing in the sequence from the lithium to cesium ions.
which can be readily obtained also from eq 1 and 3 in the limit c 0 (/3 0). In this equation the charging parameter 5 X must have its structural value. Limiting slopes calculated from
Acknowledgment. The partial financial support of the Research Community of Slovenia is gratefully acknowledged.
(16) Skerjanc, J.; HoEevar, S.;Dolar, D. Z . Phys. Chem. (Frankfurt um Main) 1973,86,3 11.
(17) Skerjanc, J.; Regent, A.; BoioviE Kocijan, L. J . Phys. Chem. 1980, 84,2584.
-+
Registry No. Poly(styrenesu1fonic acid) (homopolymer), 50851-57-5.
Temperature Dependence of the Cotton-Mouton Effects of Benzene, 1,3,5-Trifluorobenzene, and Hexafluorobenzene P. B. Lukins,la A. D. Buckingham,Ib and G . L. D. Ritchie*la School of Chemistry, University of Sydney, New South Wales 2006, Australia, and University Chemical Laboratory, Cambridge CB2 IEW, United Kingdom (Received: September 29, 1983)
Measurements of the Cotton-Mouton effects of gaseous benzene, 1,3,5-trifluorobenzene,and hexafluorobenzene over a range of temperature (~300-460K) and pressure (==lo-65 kPa) are reported. Analyses of the temperature dependences show that at normal temperatures the temperature-independentcontribution, which arises from distortion of the electronic structure by the magnetic field, is negligibly small in comparison with the temperature-dependent contribution from molecular orientation. -103.6 & 4.0; C6H3F3,-72.5 f Reliable values of the molecular magnetic anisotropy (10z9Ax/J T-') are obtained (C6H6, 5.2; C6F6,-62.7 f 2.3), and these, in combination with the known electric quadrupole moments and molecular geometries, enable other magnetic properties to be derived.
Introduction The magnetic anisotropy of a diamagnetic molecule is a fundamental property which describes the molecular charge distribution and its interaction with a magnetic field. It is closely related to other basic electric and magnetic quantities (most notably the molecular quadrupole moment, the anisotropy in the second moment of the electronic charge distribution, the diamagnetic and temperature-independent paramagnetic contributions to the magnetizability, and the molecular g value) and has been the subject of much investigation.* The widely applied microwave Zeeman-effect method of obtaining free-molecule magnetic anisotropies is inapplicable to nondipolar molecules and, as previous studies have s h o ~ n , the ~ . ~Cotton-Mouton effect is the most ~~
generally useful route to this property in such cases. There are, however, two fundamentally different origins of the observed Cotton-Mouton effect:5 first, a temperature-dependent contribution, which is dominant for anisotropic molecules, due to molecular orientation by the magnetic field and second, a temperature-independent term, which arises from distortion of the electronic structure by the field. Unfortunately, there has been, until recently: a notable lack of reliable experimental data concerning the variation of the Cotton-Mouton effect with temperature, by means of which these two contributions could be separated. Nevertheless, the Cotton-Mouton effect has been used to estimate the magnetic anisotropies of a wide range of molecules in either the gaseous3s4or dilute s ~ l u t i o nstates, ~ - ~ almost invariably
~
(1) (a) School of Chemistry, University of Sydney. (b) University Chemical Laboratory, Cambridge. (2) (a) Flygare, W. H.; Shoemaker, R. L. Symp. Faraday SOC.1969,No. 3, 119-130. (b) Flygare, W. H.; Benson, R. C. Mol. Phys. 1971,20,225-250. (c) Ditchfield, R.In "MTP International Review of Science"; Buckingham, A. D., Ed.; Butterworths: London, 1972;Phys. Chem. Ser. 1, Vol. 2,Chapter 4,pp 91-157. (d) Appleman, B. R.; Dailey, B. P. Adu. Magn. Reson. 1974, 7,231-320. (e) Flygare, W. H. Chem. Reu. 1974,7/,653-687. ( f ) Sutter, D.H.; Flygare, W. H. Top. Curr. Chem. 1976,63, 89-186. (3) (a) Buckingham, A. D.; Prichard, W. H.; Whiffen, D. H. J. Chem. SOC.,Chem. Commun. 1965,Sl. (b) Buckingham, A. D.; Prichard, W. H.; Whiffen, D. H. Trans. Faraday Soc. 1967,63,1057-1064. (c) Bogaard, M. P.;Buckingham, A. D.; Corfield, M. G.; Dunmur, D. A.; White, A. H. Chem. Phys. Lett. 1972,12, 558-559.
(4) (a) Geschka, H.; Pferrer, S.; Haussler, H.; Hiittner, W. Ber. Bunrenges. Phys. Chem. 1982,86,790-795. (b) Kling, H.; Dreier, E.; Hiittner, W. J. Chem. Phys. 1983,78,4309-4314.(c) Kling, H.; Geschka, H.; Hiittner, W. Chem. Phys. Lett. 1983,96,631-635. (5) Buckingham, A. D.;Pople, J. A. Pror. Phys. SOC.,London, Sect. B 1956,69,1133-1138. (6) Le F k e , R. J. W.; Williams, P. H.; Eckert, J. M. Aust. J. Chem. 1965, 18, 1133-1152. See also subsequent papers by Le Fevre and collaborators in the same journal, 1966-1971. (7) (a) Battaglia, M.R.; Ritchie, G. L. D. J . Chem. Soc., Faraday Trans. 2 1977,73,209-221. (b) Battaglia, M.R.; Ritchie, G. L. D. Mol. Phys. 1976, 32, 1481-1485. (c) Brereton, M. P.; Cooper, M. K.; Dennis, G. R.; Ritchie, G. L. D. Aust. J . Chem. 1981, 34, 2253-2261. (d) Ritchie, G. L. D.; Vrbancich, J. Ibid. 1982,35,869-880.
0022-3654/84/2088-2414$01.50/00 1984 American Chemical Societv
The Journal of Physical Chemistry, Vol. 88, No. 11, 1984 2415
Cotton-Mouton Effects Of C6H6, C6H3F3, and C6F6 with the assumption that the temperature-independent term is negligibly small. Not surprisingly, such results, even for strongly anisotropic molecules, have been treated with some caution; in fact, it has repeatedly been suggested that their reliability is compromised by the assumption in respect of the temperatureindependent c o n t r i b u t i ~ n . ~ ~In - ~order ~ ~ - ~to resolve these uncertainties, we have developed considerably improved equipment for measurements of the temperature and pressure dependence of magnetic birefringence in gases and vapors. Our initial investigation, described here, has been a rigorous reexamination of benzene, 1,3,5-trifluorobenzene, and hexafluorobenzene, three aromatic molecules whose magnetic properties have attracted great interest and some controversy.
Theory Application of a uniform magnetic field to a fluid induces anisotropy in the refractive index, and birefringence is observable if plane-polarized light is passed through the fluid in a perpendicular direction. The molar Cotton-Mouton constant, ,C, is defined as C , = 2nV,p2[3(n2
+ 2)2]-'[(nl, - n,)B2]E,o
= (2/27)VmP02[(nli - n L ) B 2 1 E = 0 ( l )
in which nll- n , in the field-induced refractive index difference for light polarized parallel and perpendicular to the magnetic induction B, V, is the molar volume, and M~ is the vacuum permeability. For a system of noninteracting diamagnetic molecules the theoretical expression for ,C is, in S I units5 ,c = ( N , ~ , ~ / 2 7 0 d [ 7 ~ p-, Y3vrra,p,9 ~p + (kT)-'(aafixag - 3 ~ ~ x 1(2) 1 where q is a tensor describing the dependence of the differential polarizability oh B, (Y is the optical frequency electric polarizability, x is the molecular magnetizability, and other symbols have their usual meanings. If a 3-fold or higher order rotation axis (labeled with subscript z) is present, eq 2 simplifies to
m c = W ~ P O ~ / ~ ~ O+ ~(2/3kT)AaAxI [AV
(3)
in which Aq = q)las,)lat - 1/3q,a,Bp,and A a ( = a,, - a,.,.) and Ax(= xzz- x,.,.) are the anisotropies in the molecular polarizability and magnetizability, respectively. From perturbation theory,2e*10the magnetizability of a diamagnetic molecule is
(klL,IO)
+ ( O I L ~ l k ) ( k l L a I O ) l-( ~Eo)-' ~
=X ~+ S x!& (4)
in which ri is the position vector locating the ith electron, L is the electronic orbital angular momentum operator, and Ek and Eo are eigenvalues of the field-free Hamiltonian. The magnetic anisotropy of an axially symmetric molecule is therefore expressible in the form
Ax = Axd + AxP
(5)
and since Axd can be written in terms of the molecular geometry and the electric quadrupole moment, 8, as
a knowledge of these latter properties makes possible the separation of Ax into diamagnetic and temperature-independent paramagnetic contributions. In addition, the anisotropy, gz, - l / f i x , . , in the molecular g value, which relates the rotational angular mo(8) Schmalz, T. G.;Norris, C. L.; Flygare, w. H. J. Am. Chem. Soc. 1973, 95, 7961-7967. (9) (a) Plantenga, T. M.; Bulsink, H.; MacLean, C.; Lohman, J. A. B. Chem. Phys. 1981,61, 271-280, (b) Luyten, P. R.; Bulthuis, J.; MacLean, C. Chem. Phys. Lett. 1982,89, 287-290. (10) Buckingham, A. D.; Cordle, J. E. Mol. Phys. 1974, 28, 1037-1047.
Figure 1. Optical system for measurements of magnetic birefringence: L, IO-mW He-Cd laser (441.6 nm); F, variable neutral density filter; PI and P2, crossed 13-mm-edge Oriel calcite polarizers, transmission axis of PI at 45O to direction of magnetic field; M, magnet; C, cell; Q, quarter-wave plate; CC, compensation coil; CR, and CR2, current regulators; MC, modulation coil; LF, laser line filter; PM, photomultiplier tube; PS, power supply; PA, power amplifier; 0, oscillator; LI, lock-in analyzer; R, recorder; MP, microprocessor; CRO, oscilloscope.
mentum to the magnetic moment, is accessible; for a planar, axially symmetric molecule this quantity is given by the gzz
-
k x x
= -(Mp/eZzz)[(4me/e)A~
+ el
(7)
where ZZz is the moment of inertia for rotation about the symmetry axis. It is clear from the foregoing that if the arrangement in space of the nuclei and also the molecular quadrupole moment are known, the magnetic anisotropy can yield useful information concerning the electric charge distribution.
Experimental Section The apparatus, shown in Figures 1 and 2, which we have assembled in Sydney to measure the temperature dependence of magnetic birefringence in gases is an improved version of the arrangement originally described by Buckingham, Prichard, and W h i f f e r ~ .In ~ ~terms of overall performance, an improvement of at least an order of magnitude has been gained through better resolution and accuracy in the detection of small birefringences, more accurate system calibrations, an extended temperature range, and the use of a He-Cd, rather than a He-Ne, laser. A frame constructed from 20 cm X 10 cm X 0.64 cm rectangular steel tubing supports the magnet and the two optical subframes; the subframes and the stands for the optical components are adjustable and of tripod design, so that mechanical stability is enhanced. The optical system (Figure 1) is similar to that used in earlier studies. A Liconix Model 4210 He-Cd laser provides 10 mW at 441.6 nm, and a variable neutral density filter reduces the transmitted power to a level consistent with linear photomultiplier tube operation. The ellipticity induced in the light beam by the magnetic field is converted by a quarter-wave plate to an optical rotation which is in turn nulled by a Faraday coil driven by a Kepco Model CC72-0.3M 300-mA variable-current regulator. A second Faraday coil, powered by a BWD Model 141 sine-wave oscillator and a 60-W-power amplifier, serves to modulate the transmitted light at 325 Hz with an amplitude of = rad. Stray light and electromagnetic interference are excluded from the EM1 9658B photomultiplier tube by a laser line filter and a p m e t a l shield. The photomultiplier output signal is monitored by an oscilloscope, and the fundamental component is detected by an Ithaco Dynatrac Model 393 lock-in analyzer; further conditioning and display are provided by a microprocessor and a chart recorder. Application of the Mueller-Jones calculus12 facilitates optimization of the performance of the optical system and allows an analysis of errors to be made. Prism and quater-wave plate errors are reduced to 98%) and hexafluorobenzene (Fluka, >99%), both twice distilled from phosphorus pentoxide, estimated purities 199% and 199.5%, respectively, by gas chromatography. In addition, the samples were subjected to several freeze-pump-thaw-distill cycles in the vapor-handling system immediately prior to the commencement of each set of pressure-dependence measurements.
Results and Discussion The experimental results are summarized in Table I. Measurements of the magnetic field induced birefringences of the vapors were made at six or more temperatures spanning the attainable range (-300-460 K) and, at each temperature, over a range of pressures (up to -65 kPa). As can be seen from Table I, several hundred observations were made on each compound. Recorded density virial coeffi~ients'~ were used to calculate gas densities from the pressures and, because the experiments were ( 1 3) Dymond, J. H.; Smith, E. B. 'The Virial Coefficients of Pure Gases and Mixtures"; Clarendon Press: Oxford, 1980. Values for 1,3,S-trifluorobenzene were estimated as the means of the corresponding values for benzene and hexafluorobenzene.
Cotton-Mouton Effects Of C&,
The Journal of Physical Chemistry, Vol. 88, No. 11, 1984 2417
C6H3F3, and C,5F,5
TABLE 11: Analysis of the Temperature Dependence of the Cotton-Mouton Effects of Benzene, 1,3,5-Trifluorobenzene,and Hexafluorobenzene
c, H3F3
C 6 H 6
IOz4
X X
slope/m5 A-' K mol-'
intercept/m5 A-' mol'' lo4' Aa/C m2 V-' 1029 A ~ / J~
-
2
IOgo o/C m' 1040e~Z,(z,' n
- x n 2 ) / C m'
-1040e(01~(zi2 - xi2)10)/C m2
13.41 f 0.44 -1.6 i 1.2 -6.74 f 0.14 -103.6 f 4.0 -29.0 i 1.7 -858.7
9.84
6'
F6
8.98 * 0.1 9 -0.06 f 0.52 -7.46 i 0.22 -62.7 f 2.3 31.7 * 1.7 -3772.1
0.64 -0.3 i 1.8 -7.07 f 0.21 -72.5 i 5.2 3.1 f 0.4 -2315.7 i
829.7
2318.8
3804.4
-364.8 261.2 29.534 0.0935 i 0.0033
-1019.6 947.1 96.676 0.0175 ?: 0.0013
-1672.8 1610.1 163.817 0.0071 i 0.0004
1
TABLE 111: Experimental Values of the Magnetic Anisotropies, IO2'Ax/J T-', of Benzene, 1,3,5-Trifluorobenzene,and Hexafluorobenzene ' 6 H6 C6H3F3 ref direct measurements on crystals -99.1 17a -101.0 17b magnetic birefringence, vapor state -89 i 4 -65 i 3 -53 f 2 3c 4a -103.8 ?: 3.3 -103.6 * 4.0 -12.5 t 5.2 -62.7 * 2.3 present work -106 i 4 -69.4 i 3.0 -64.1 f 2.8 7a,d magnetic birefringence, dilute-solution state -104 f 3 -58 i 5 16 magnetic birefringence, liquid state 'H NMR line splitting, solution state -40 9b -105 semiempirical estimates from Zeeman-effect 18a 18b anisotropies of related molecules -104 conducted at relatively low pressures, second Cotton-Mouton virial coefficients5 were not discernible. The uncertainties shown in Table I are based on the standard deviations derived from the least-squares fitting of straight lines to the density-dependence data but also incorporate appropriate allowance for the systematic errors mentioned above. From eq 3, is is clear that the molar Cotton-Mouton constant should exhibit a linear dependence on the reciprocal of the absolute temperature, and plots of C , against T I are shown in Figure 3. The slopes and intercepts are given in Table 11, which also contains a detailed analysis of the derived magnetic anisotropies and related properties of these molecules. It is immediately obvious from the intercepts that in all three cases the temperature-independent contribution to the CottonMouton constant is very small at normal temperatures. At 298 K, the percentages of ,C originating in A7 are as follows: C6H6, -4 f 3; C6H3F3, -1 f 6; C6F6, -O 2%. Although C6H6 appears to exhibit a slightly negative intercept when the uncertainty is quoted at the level of the standard deviation, we feel that a definite inference would not be justified. In support of this view, we note that the recent study of the temperature dependence of the magnetic birefringence of benzene by Geschka, Pferrer, Haussler, and H i i t t ~ ~yielded e r ~ ~ the corresponding proportion of ,C at 298 K as 4 f 8%. It is worthy of particular emphasis here that the experimental determination, with acceptable precision, of the temperature-independent contribution to the Cotton-Mouton constant is an extremely demanding objective, because a long and therefore somewhat uncertain extrapolation to T I = 0 is generally required. Nevertheless, the present study shows that for these three molecules such contributions are negligibly small. We believe, furthermore, that these findings are likely to be typical of aromatic or other highly anisotropic molecules. In order to deduce the magnetic anisotropies, Ax, from the it was necessary to evaluate slopes of the plots of ,C against TI, the corresponding polarizability anisotropies, Aa,at 441.6 nm. For frequencies, u, small relative to absorption frequencies, Aa is a linear function of v2,I4 so that extrapolation of anisotropies determined from Rayleigh depolarization ratios15for other visible
I
r
+
20
2.5
3.0
3.5
3.0
3.5
+
(14) Alms, G. R.; Burnham, A. K.; Flygare, W. H. J. Chem. Phys. 1975, 63, 3321-3326. (15) Bogaard, M. P.; Buckingham, A. D.; Pierens, R.K.; White, A. H. J. Chem. Soc., Faraday Trans. 1 1978, 74, 3008-3015.
-51
2.0
2.5 1O ~ TIK '--
Figure 3. Temperature dependence of the vapor-state Cotton-Mouton effects of benzene, 1,3,5-trifluorobenzene,and hexafluorobenzene.
wavelengths readily provides the required information, shown in Table 11. The derived magnetic anisotropies are compared with previous estimates in Table 111. It is apparent that our values for benzene and hexafluorobenzene, and to a lesser extent for 1,3,5-trifluorobenzene, are significantly different from those found in the original study of vapor phase magnetic b i r e f r i n g e n ~ eand ~~ that our result for benzene is in agreement with that in the more recent Although both previous i n v e s t i g a t i o r ~ were s~~~~~ temperature-dependence studies, the quoted magnetic anisotropies
2418
J. Phys. Chem. 1984, 88, 2418-2422
were, in fact, derived with the assumption that A7 = 0, a procedure which obviously has the effect of greatly reducing the apparent uncertainty in the slope of the plot of ,C against T1.No such approximation was made in the present analysis, and our results can therefore be considered to be by far the most reliable. Two further points of interest in relation to Table 111 are that the magnetic anisotropies obtained for these molecules through the application of dilute-solution' or pure-liquid16procedures, in which it is assumed that A7 = 0, are in good agreement with the present results and that, in the case of benzene, results similar to ours were deducd from measurements on crystals17and, indirectly, from Zeeman-effect anisotropies of related molecules such as fluorobenzene.ls A knowledge of the electric quadrupole moments and dimensions of the molecules under study makes possible the decomposition of the observed magnetic anisotropies into the oppositely signed diamagnetic and temperature-independent paramagnetic contributions and permits the evaluation of a measure of the anisotropy in the rotational g value. Values given for the quadrupole moments of these nondipolar molecules are those determined by measurement of the birefringence induced in the vapor" (or, in the case of 1,3,5-trifluorobenzene, in dilute solution^^^) by ~
~
an electric field gradient. The nuclear contributions to the quadrupole moments and the moments of inertia were calculated from the known geometries of benzenez0and hexafluorobenzene.21 Reliable values of these derived magnetic properties have not previously been available, and they are of interest because of the insight which they provide into the molecular charge distributions.
Summary The present study of the temperature dependence of vapor-state magnetic birefringence has demonstrated that for benzene, 1,3,5-trifluorobenzene, and hexafluorobenzene the temperatureindependent contributions to the Cotton-Mouton effects at normal temperatures are negligibly small. Reliable values of the molecular magnetic anisotropies have also been obtained and these, in combination with the known electric quadrupole moments and molecular geometries, permit the anisotropies in the molecular diamagnetizability, the temperature-independent paramagnetizability and the rotational g value to be determined. Acknowledgment. The award of a University of Sydney Special Project Research Scholarship (to P.B.L.), financial support from the Australian Research Grants Scheme (to G.L.D.R.), and helpful conversations with Dr. M. P. Bogaard (University of New South Wales) are gratefully acknowledged.
~~~~~
(16) Battaglia, M. R. Chem. Phys. Lett. 1978, 54, 124-127. (17) (a) Hoarau, J.; Lumbroso, N.; Pacault, A. C. R. Hebd. Seances Acad. Sci. 1956,242, 1702-1704. (b) Van den Bossche, G.; Sobry, R. Acta Crystallogr., Sect. A 1974, A30, 616-625. (18) (a) Sutter, D. Z . Naturforsch., A 1971 26A, 1644-1657. (b) Rock,
S.L.; Pearson, E. F.; Appleman, E. H.; Norris, C. L.; Flygare, W. H. J . Chem. P h p . 1973, 59, 3940-3945.
Registry
NO.
C6H6, 71-43-2; C6H3F3, 372-38-3; C6F5, 392-56-3.
(19) Vrbancich, J.; Ritchie, G. L. D. J . Chem. SOC.,Faraday Trans. 2 1980, 76, 648-659. (20) Langseth, A.; Stoicheff, B. P. Can. J. Phys. 1956, 34, 350-353. (21) Almenningen, A.; Bastiansen, 0.;Seip, R.; Seip, H. M. Acta Chem. Scand. 1964, 18, 2115-2124.
Electron-Transfer Quenching of Ruthenium(I I ) Photosensitizers by Mercury( I I ) in Aqueous Nitrate Media B. L. Hauenstein, Jr., W. J. Dressick, J. N. Demas,* Department of Chemistry, University of Virginia, Charlottesville, Virginia 22901
and B. A. DeCraff* Department of Chemistry, James Madison University, Harrisonburg, Virginia 22807 (Received: July 6, 1983)
Excited-state interactions of tris(a-diimine)ruthenium(II) photosensitizers with HgZf were studied in aqueous nitrate media by using luminescence quenching and flash photolysis methods. Quenching proceeds via oxidative electron transfer to yield Ru(II1) and a Hg(1) free radical with high efficiency. Regardless of the excited-state reducing power of the photosensitizer, quenching was near but below the Marcus diffusion-controlled limit. Dimerization of the Hg(1) free radical to give Hgzz+ competes effectively with the diffusion-limited back-electron-transfer reaction of the free radical with the Ru(II1) species. The back-reaction rate of Hg?' and Ru(II1) is much slower and depends on Eo(Ru(III/II)). The efficiency of electrontransferred-product separation is sensitive to Eo(Ru(III/II)), The mechanism of the oxidation of Hg?+ by Ru(II1) is discussed.
Introduction The photochemistry of platinum metal complexes is an active area of investigation because of the potential of these systems in solar-energy conversion.' Energy-conversion research with photogalvanic cells has concentrated on systems that exhibit reversible excited-state electron-transfer reactions. For useful storage of chemical energy, the production efficiency of redox products (1) For a general overview see: (a) Kalyanasundaram, K.; Gratzel, M. NATO Ado. Study Inst. Ser., Ser. B 1981, 69, 349. (b) Kalyanasundaram, K. Coord. Chem. Rev. 1982,46, 159.
must be high and the thermal back-reaction must be slow. The latter requirement and prevention of photodegradation have proven to be major problems. Storage of energy in the redox partners in homogeneous media has typically been limited to seconds due to the rapidity of the back-reaction. Recently, we reported an energy-trapping and -conversion system based on quenching by Hgzf.z The proposed reaction sequence is given by D
+ hv-+
*D
(4')
(1)
(2) DeGraff, B. A,; Demas, J. N. J. Am. Chem. SOC.1980, 102, 6169.
0022-3654/84/2088-2418$01.50/00 1984 American Chemical Society
