J. Phys. Chem. 1992,96, 5793-5796
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Future Investigation
either the lithium-6, deuterium, or the boron spectra.
The next step in our efforts is to incorporate the cluster mathematics of this publication into algorithms that deal with sets of clusters. In the usual notation of NMR we have dealt here with the A,,A situation. Sets of clusters would lead to AnA, BnB, CnC,...,G d situations and then to the calculation of NMR spectra for quadrupolar nuclei. We have now developed the theoretical background for closed expressions for calculating the coupling eigenvalues for systems with geometric ~ymmetries.'~ This development should be especially useful in calculating NMR spectra for boron compounds. We suggest that NMR studies of lithium-boron coupling could be especially fruitful for investigation of higher rank coupling. Lithium-6 has a very small quadrupole moment and has been predicted to have almost proton-like spectra with respect to resolution.'6 The same reference reports sodium, boron coupling in sodium borohydride in spite of what might be expected in the way of ionic bonding with no coupling. Lithium compounds should be less ionic than sodium compounds. Unfortunately the clearest results could probably be obtained only with isotopically pure lithium-6 and boron-1 1 in the lithium borohydride. The borodeuteride anion also offers some advantages in the boron-11 NMR spectrum without requiring isotopic purity. In these situations, since deuterium and lithium-6 are spin 1 nuclei, second rank coupling would be the highest rank coupling that could occur in
References and Notes (1) Siddall, T. H., I11 J. Phys. Chem. 1982, 86, 91. (2) Fano, U.; Racah, J. Irreducible Tensorial Sets; Academic Press: New York, 1959. (3) Cono, P. L. Structure Of High Resolution NMR Spectra; Academic Press: New York, 1966. (4) Emsley, J. W.; Fetney, J.; Sutcliffe, L. H. High Resolution Magnetic Resonance Spectroscopy; Pergamon Press: New York, 1965. (5) Abraham, R. J. The Analysis Of High Resolution NMR Spectra; Elsevier Publishing Company: New York, 1971. (6) Cotton, F. Albert Chemical Applications Of Group Theory, 2nd 4.; Wiley-Interscience: New York, 1971. (7) Hamermesh, Morton Group Theory And Its Application To Physical Problems; Addison-Wesley: Reading, MA, 1962. (8) Wyboume, B. G. Classfcal Groups For Physicists; Wiley-Interscience: New York, 1974. (9) Wybourne, B. G . Symmetry Principles And Atomic Spectroscopy; Wiley-Interscience: New York, 1971, (10) Siddall, T. H., 111; Flurry, R. L., Jr. J. Magn. Reson. 1980,39,487. (1 1) Silver, B. L. Irreducible Tensor Methods An Introduction For Chemists; Academic Press: New York, 1976. (12) Wilson, E. Bright, Jr.; Decius, J. C.; Cross, P. C. Molecular Vibrations, The Theory Of Infrared And Roman Vibrational Spectra; McGrawHill: New York, 1955. (13) Louck, J. D. Am. J. Phys. 1970,38, 3. (14) Sullivan, J. J.; Siddall, T. H., 111 J . Math. Phys., in press. (15) Griffith, J. S.Struct. Bonding (Berlin) 1972, 10, 87. (16) Sidle, A. R. Annual Reports On NMR Spectroscopy; Academic Press: New York, 1988; Vol. 20.
Fourier Transform Infrared Spectra of the Complexes XCN-HF Isolated in an Argon Matrix
(X = F, CF,, SF,)
Jirgen Jacobs, Helge Willner,* Institut far Anorganische Chemie der Universitiit Hannover, Callinstrasse 9, 0-3000 Hannover 1. FRG
and Gottfried Pawelke Bergische Universitdt Wuppertal. Anorganische Chemie, Gaussstrasse 20, 0-5600 Wuppertal, FRG (Received: January 14, 1992; In Final Form: March 30, 1992)
Complexes of nitriles XCN (X = F, CF,, SFS)with HF (DF) isolated in an argon matrix have been studied by means of FTIR spectroscopy. The linear complexes XCN-HF were formed by mixing the components in the gas phase and condensing the mixtures on the matrix support. The frequencies of the stretching vibrations (v,) of the HF (DF) submolecule were found to be 3662 (2694), 3733 (2742), and 3728 (2739) cm-' for FCN, CF,CN, and SF5CN,respectively. This sequence correlates with the frequencies for the librational modes vl, being 554 (408), 493 (369), and 486 (358) an-*.Photolysis of matrix-isolated CF2NH produced the complex FCN-HF in a high yield enabling the measurement of the vibrational mode of the hydrogen bond (v,) at 171 cm-'. Furthermore, the complexes of ClCN, BrCN, and NCCN with HF (DF) have been reinvestigated.
Introduction Because of its importance in chemistry and biology, hydrogen bonding is of general interest. Simple model systems are hydrogen-bonded complexes of small basic molecules with HF, as H F forms strong hydrogen bonds and these complexes give relatively simple IR spectra.' With nitriles, XCN, different kinds of complexes can be formed in principle: (a) H F is a-bonded to the lone pair at the nitrogen atom (X-N-HF); (b) H F is *-bonded to the triple bond system (side-on bonded); (c) HF is a-bonded to the X atom (NEC-X-.H-F) and in the special case X = H, H F may act as a base (NEC-H.-.F-H).Z Several XCN/HF complexes isolated in an Ar matrix have been investigated by FI'IR spectroscopy with the substituent being H: halogens and CN,3" NH2 and N(CH3)2: and alkyls."' In all cases, To whom correspondence should be addressed.
0022-365419212096-5793$03.00/0
the most stable form is XCN-HF (a). The complexes of XCN (X being H, D, CH,, CD,, and (CH,),C) with H F and DF have been studied extensively in the gas phase by microwave and infrared ~pectroscopy.*-'~ The formation of a hydrogen bond between XCN and H F in a complex of type a has consequences for the vibrational spectra of the two submolecules because the free electron pair of the nitrogen atom is donated into the a* orbital of the HF molecule. Therefore, the stretching frequency of H F is shifted to lower wavenumbers, while that of the CN group should be shifted to higher frequency.6 The red shift of v(HF) will be larger the stronger the hydrogen bond is. Therefore, Av(HF) can be used as a measure of the strength of the hydrogen bond. In addition to these frequency shifts, some new vibrational modes are expected as 3 degrees of freedom from translation and 2 of rotation are converted into 5 of vibration if a linear complex 0 1992 American Chemical Society
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The Journal of Physical Chemistry, Vol. 96, No. 14, 199‘2
is assumed. The most evident of these is the vibrational mode of the hydrogen bond between the nitrogen and the hydrogen atom itself (v,). (The nomenclature for the complex vibrations is according to ref 7.) Since the bonding is weak, this frequency is expected in the far-infrared region below 200 an-]and it will show low infrared intensity. Despite extensive investigations into complexes of the type XCN-HF, it has not been possible to determine v, in a matrix isolation experiment so far. The other four vibrations fall into two 2-fold degenerate librational modes, one in-phase (v,) and one counterphase (vs) bending motion of the two submolecules with respect to each other. Only the in-phase motion is easily detectable because of its high infrared intensity. The counterphase motion shows low infrared intensity and is expected in the far-IR region below 100 cm-I, as determined in the complexes of CO with HF.I4 All complexes which have been studied so far were prepared by mixing the components (XCN, HF, Ar) in the gas phase and condensing them on a matrix support at about 10 K, or by mixing XCN and H F (DF) separately with Ar and cocondensing these mixtures. The only exception was the preparation of the complex FCN-HF by photolysis of HCN (DCN)/F2 mixtures isolated in an Ar matrixa4This method produced the complex in low yield besides many byproducts; hence the assignments were not unambiguous and v,(DF) was not observed. The aim of this study was to measure the fundamentals of FCN-qHF as completely as possible and to investigate the analogous unknown complexes of CF3CN and SF5CN. Because these substituents are most important in fluorine chemistry, our results will enable us to describe the substitutional effect of F, CF3, and SF5 on the basicity of the nitrile nitrogen atom.
Experimental Section chemicals. Hydrogen and deuterium fluoride were synthesized by heating an excess of H2S04(D2S04)with anhydrous NaF to 200 OC in a stainless steel cylinder. The volatile impurities were removed from the trapped H F (DF) at -80 OC in vacuo. FCN,15 CICN,16 BrCN,” (CN)2,18SF5CN,I9CF3CN,20and CF2NH2’were prepared according to literature methods and purified by trap-to-trap condensation. Since CF2NH is very sensitive toward acidified surfaces, the vacuum line was cleaned with hot water, dried in vacuo, and treated with (C2H5)3Nvapor prior to use. Instrumentation. All (XCN/HF (DF)/Ar) mixtures were prepared in a passivated stainlesskeel high vacuum line that had been treated with ClF3 to remove traces of water and which was well passivated with H F or DF. The mixtures were transferred through a stainlesS steel capillary to the matrix support; the gas flow was controlled by a needle valve. CF2NH was handled in a Duran glass system and transferred through a quartz glass capillary. The matrix support was a highly reflecting, aluminum-covered copper block that could be cooled down to a minimum temperature of 4 K by the aid of a liquid helium continuous-flow cryostat (Cryovac, Troisdorf, FRG). The mid- and far-IR spectra were recorded on two FTIR spectrometers: a IFS 66v and a IFS 113v (Bruker, Karlsruhe, FRG) at a resolution of 1 cm-l (5000-400 cm-I) and 4 cm-I (400-50 cm-I). A DTGS detector was used for the region 500(>-400 cm-l and a liquid helium cooled Ge bolometer was used for the region 370-50 cm-I.
Results and Discussion FCN and HF (DF). For a reference spectrum, 0.44 mmol matrix of a 1:400 mixture of FCN/Ar were deposited on the matrix support at 12.5 K with a deposition rate of 1.O mmol/h. The resulting IR spectrum was used to assign the bands of free FCN in the spectra obtained for FCN/HF (DF) mixtures. The fundamental vibrations of FCN showed only slight gas-to-matrix shifts; the observed frequencies are (gas phase values in parentheses): vlr 2316 (2319); u2, 1076 (1077 cm-’); u3, 456 (451) cm-I. For preparation of the FCN/HF complexes, 1.94 mmol of a sample of FCN/HF/Ar (1:3:500) were condensed at 12.5
Jacobs et al. TABLE I: Vibratiod Frequencies [cm-’1 of the Complex FCN-HF, Prepared by two Different Routes, and of FCN Isolated in an Ar Matrix
FCN and HF (DF) deposited FCN-HF FCN-DF
FCN
3662 2355 1107 554 458
2316 1076 456
00
assignments in the point
“2”
photolyzed
FCN-**HF
2694 2356 1107 408 460
PrOUD
1
RJ-AL A a
4M)o 3900 3800 3703 3600
a
a
24”
.
c-
v,(HF/DF) v,(FCN);VC(CN) v~(FCN); vC(CF) u,(FCN*HF) vI(FCN);6‘(FCN) v,(N-*H)
3663 2355 1107 553 458 17 1
a
, i
1100
6 0 3 7 6 Wavenumber [cm.’]
Figure 1. FlTR spectra of the complex FCN-HF isolated in solid argon produced in different ways: (a) after condensation of 1.94 mmol of a mixture FCN/HF/Ar (1:3:500); (b) photolysis of 2.69 mmol of CFINH with a medium-pressure arc lamp for 3 h; (c) annealing the matrix of photolyzed CF2NH at 30 K for 1 min.
K with a deposition rate of 2.5 mmol/h. The experiment was repeated using DF instead of HF. The results are presented in Table I and Figure la. Many of the new bands which did not occur in the pure FCN sample or could be assigned to monomeric or oligomeric H F (DF)22are due to the FCN/HF (DF) complexes. The reported wavenumbers for FCN-HF (DF)4 were confirmed. The v, bands occurred at 3662 (2694) cm-’ and the librational modes vI could be identified at 554 and 408 cm-I, respectively. For the DF complex vI was not observed in ref 4 but calculated to be 409 f 3 cm-I. Furthermore, all three FCN fundamental vibrations showed satellite bands. In addition to v l a further band (ulc) (the superscript c refers to the complex) was found at 2355 and at 2356 cm-I for experiments conducted using H F and DF, respectively. The v2 satellite occurred at the same frequency for the H and D species, at 1107 cm-I. The v3 satellite was at slightly higher wavenumber for FCN-DF than for FCN-HF (460 and 458 an-’, respectively). The large blue shift for v 1 (v(CN)) indicates a nitrogen-bonded complex, and the observation of only one librational mode v, proves the linearity of the complex F-N-H-F (&). The large blue shift for v2 (v(CF)) is due mainly to an increase of the CF bond strength. The blue shift for v2 by vibrational coupling between vl and v2 is small as deduced from a model calculation. For photochemical synthesis of this complex, 2.69 mmol of a sample of CF2NH/Ar (1:500) containing a small amount of CF2ND was condensed at 1 1.5 K with a deposition rate of 3.4 mmol/h. Because the IR spectra of CF2NH and CF2ND were known only in the gas phase and the band position of v6 was uncertain, the complete vibrational data are given in Table 11. The spectrum of CF2NH was recorded as background for the spectrum after photolysis with a medium-pressure mercury arc lamp TQ 150 (Heraeus, Hanau, Germany), for a total period of 3 h. The process of decomposition was controlled by measuring IR spectra as a function of time. The resulting spectrum (Figure lb) was much simpler than that obtained by mixing FCN and HF (DF) in the gas phase (Figure la). No free HF, (HF),, and only very little free FCN could be
FTIR Spectra of XCN-HF
The Journal of Physical Chemistry, Vol. 96, No. 14, 1992 5195
TABLE Ik Infrared Data [cm-l] for CF2NH and CFIND CFZNH
CFZND
assignments in the point group C, 2508 vl(a’); u(NH/D) 1772 vz(al);v(CN)
gas Ar gas Ar phase” intb matrix phase“ intb matrix 3402 1785 1307 1031 947 542 832 695
0.15 0.86 0.01 1.00 0.43 0.01 0.36 0.03 0.17 0.46 0.07
” Reference 21.
3388 1777 1733 1295 1027 1023 942 574 542 828 694
2519 1780 1280 836 954 492 614 705
0.16 0.64 0.01 1.00 0.23 0.23 0.01 0.14 0.17 0.19
1731 1267 833 951 565 491 612 703
~ 2 13C ,
+(a’); v,,(CFz) v,(a’); I(CNH/D) Y4, I3C vs(a’); v, (CF,) u6(a’); 6EF2) w7(a1’);p(CFz) vs(a”); s(NH/D) v9(a’’); y(CF2)
Integrated intensities relative to I(v3) 1 .OO.
TABLE III: IR Spectrum of CF3CN [cm-’1
gas phase’
Ar matrixb
assignments in the point ErOUD c2,
observed. The band at 3663 (2694)cm-’ was accompanied by a second sharp, even more intense band at 3669 (2698)an-’;and vIC(FCN) showed a neighbor at 2352 an-’.Finally, the librational mode vI (HF) was also accompanied by a more intense band at 546 cm-I. None of these bands was observed in the former experiment suggesting a second kind of complex between FCN and H F (labeled B); this being slightly weaker bonded than the already discussed complex (labeled A). The reason for its formation may be that the ideal orientation for the FCN.-HF complex may not be achievable for all molecule-pairs present in the matrix. In the far-IR spectra below 400 cm-’ a broad and very weak band at 171 cm-’ was found which increased in intensity with continuing photolysis. There is no doubt that this band belongs to the FCN/HF complex; it was assigned to Y,. On annealing the matrix for 1 min at 30 K and subsequent recooling to 12 K, the bands assigned to complex B disappeared completely while those for complex A (including the vibrations of the FCN submolecule) decreased only slightly in intensity and some unidentified new bands appeared at 3685,3676,3605,3529, 3514, 3507,2362,and 651 cm-I. Warming up the matrix led to reorientation of the Ar atoms around the matrix cage. The complex B which was due to an unstable site disappeared completely and other (so far unknown) species were formed besides the linear one FCN.-HF (A). CFjCN and HF (DF). Three experiments were performed to measure the IR bands of CF3CN and the respective H F (DF) complexes. A sample of CF3CN/Ar (1 500,0.70 mmol) was deposited at 12 K and the resulting frequencies are listed in Table I11 together with the gas phase data. In another experiment 1.76 mmol of a mixture of CF3CN/ HF/Ar (1:3:500)was condensed at 12.0 K on the matrix support with a deposition rate of 5.3 mmol/h. A further matrix was formed by condensing 2.64 mmol of CF3CN/DF/Ar (1:3:500) with 3.8 mmol/h at 14 K. The resulting vibrational data are listed in Table IV. Several new bands apart from those belonging to monomeric or oligomeric H F (DF) and CF3CN were found. In both spectra of the H F (DF) complexes the absorption assigned to v, was split into two bands; a stronger one at 3733 (2742)cm-’ and a slightly weaker one at 3740 (2746)cm-I. The same is true for the li-
TABLE Iv: Vibrational Shifts [cm-’1 of v(HF/DF) and u(CN) by Complex Formation XCN-HF (DF) in Ar Matrix and the Librational Frequencies vl(HF/DF) [em-’] of the Complexes (v
XCN CD$N ClCN ICN HCN BrCN FCN SFsCN CF$N NCCN
- v,)
HF* HF 437 324 31 1 295 286 258 192 187 163
(Y’ Y
- v)
CN VI --
DF (CN)* . , HF 305 2267 38 228 2209 38 218 208 2095 28 202 2190 39 182 2316 39 137 2237 19 134 2272 20 11 119 2154
DF HF 39 68 1 38 603 590 28 586 39 572 40 554 20 486 20 493 1 1 459
DF -500 449 438 434 428 408 358 369 338
refs
7 3c 3 2 3c
this work this work this work 3c
“Values for uncomplexed HF (DF) (Q branch) are 3919.5 (2876.4) cm-1>2 Values of the uncomplexed XCN molecules. Confirmed and completed by own measurements. brational modes Y/,which were observed at 493 (369)cm-’ and 476 (357) an-1.In both spectra a band at 2292 cm-’ with a small side band at 2306 cm-’ appeared next to the split band of uncomplexed CF3CN at 2272 cm-I. This band can clearly be assigned to vIC(CF3CN). In the case of FCN, the blue shift of w(CN) is an indicator of the strength of bonding of H F (DF) to the nitrogen atom. The observed splitting of the librational modes vI could be due to a nonlinear complex. Since there was also a splitting observed for us, two slightly different complexes seem to be a more convenient explanation. The weaker bands can be assigned to a slightly weaker bonded complex, as Av(HF) and Y / are lower. This complex may arise due to different matrix sites. In general, CF3CN shows splitting of all fundamentals; split complex absorptions are observed also for the complex between acetonitrile and H F isolated in an Ar but not in the gas phase.g Therefore, the complex can be presumed to have linear structure (C3”). SF&N and HF (DF). The IR spectrum of SF5CN isolated in an Ne matrix has been reported previo~sly.’~However, the frequencies in an Ar matrix differ slightly from those in a Ne matrix. Therefore a 1.80mmol matrix (SF,CN/Ar = 1:700)was formed at 12 K with a deposition rate of 5.1 mmol/h and an IR spectrum was recorded and used as blank for the mixing experiments. SF5CN was mixed with HF and Ar (1:3:500)and 1.76 mmol was deposited with a rate of 5.0 mmol/h on the cold surface at 12.5 K. An analogous experiment was performed with DF (3.52 mmol matrix with 3.2 mmol/h at 14.0 K). As with CF3CN,several new bands appeared which are listed in Table IV. In contrast to CF3CN-.HF, only one absorption at 3728 cm-’ could be found in the region of H F vibrational modes with a DF counterpart at 2739 cm-I. Apart from the v1 fundamental of SFSCNat 2237 cm-l, one sharp band appeared at 2256 (2257)cm-’ ( u l C ) . For the librational modes there was also no splitting observed, they were found to occur at 486 and 358 cm-’ for H F and DF, respectively. In the region of S F vibrational modes no additional bands could be detected. Again, the large value for Av(CN) shows that H F (DF) was bonded to the nitroaen atom. As there is no sDlittinn of librational modes, it is obviousihat the complex should have a &ear structure SFSCN.**HF(C4”).
Conclusions The crucial vibrational data of the above discussed linear HF (DF) complexes with FCN, CF3CN, and SF5CN, together with literature data of other important nitrile complexes, are ordered by decreasing (v - v,) (HF) in Table IV. For the ClCN, BrCN, and (CN), complexes these data have been reinvestigated and completed in the course of this work. On the basis of all data some observations are of interest and conclusions about the in-
J . Phys. Chem. 1992, 96, 5796-5800
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In all cases the blue shift is increased by deuteriation. On deuteriation the strength of the hydrogen bond is increased, implying that something else is responsible for the change in u(CN) shifts. One can assume that the answer lies in the antibonding character of the nitrogen free electron pair which is influenced by the substituents. If one normalizes the blue shifts on the strength of the hydrogen bonds (Av(CN) divided by vI or Av(HF)) one can give the following order of X for decreasing antibonding influence of the nitrogen free electron pair in the CN bond: F > Br > C1 > CH3 > H > SFS CF3 > CN. (iv) The free energy of complex formation cannot be correlated with the strength of the hydrogen bond because the energy of the XCN submolecule is altered. This point was discussed earlier on the example OC.-HF and CO--HF.'4
1
450
References and Notes (1) Andrews, L. J. Phys. Chem. 1984,88,2940. (2) Andrews, L.; Hunt, R. D. J. Phys. Chem. 1988, 92, 81. (3) Hunt, R. D.; Andrews, L. J. Phys. Chem. 1987, 91,5594. (4) Hunt, R. D.; Andrews, L. Inorg. Chem. 1987, 26, 3051. (5) Hunt, R. D.; Andrews, L. J. Phys. Chem. 1987, 91, 2751. (6) Davis, S. D.; Andrews, L. J. Mol. Spectrosc. 1985, 1 1 1 , 219. (7) Johnson, G. L.; Andrews, L. J. Phys. Chem. 1983,87, 1852. (8) For an overview, see for example: Bevan, J. K. NATO ASI Ser., Ser. C 1987, no. 212, 149. (9) Thomas, R. K. Proc. R.SOC.London 1971, 325, 133. (10) Georgiou, A. S.,Legon, A. C.; Millen, D. J. Proc. R. Soc. London A 1980, 370, 257. (1 1) Wang, F. M.; Iqbal, K.; Kraft, H.G.; Luckstead, M.; Eue,W. C.; Bevan, J. W. Can. J. Chem. 1982, 60, 1969. (12) Wofford, B. A,; Jackson, M. W.; Lieb, S. G.; Bevan, J. W. J. Chem. Phys. 1988,89, 2775. (13) Wofford, B. A.; Ram, R. S.; Quinonez, A.; Bevan, J. W.; Olson, W. B.; Lafferty, W. J. Chem. Phys. Lett. 1988, 152, 299. (14) Schatte, G.; Willner, H.; Hoge, D.; Kn6zinger, E.; Schrems, 0. J. Phys. Chem. 1989, 93, 6025. (IS) Fawcett, F. S.;Lipscomb, R. D. J. Am. Chem. Soc. 1964,86,2576. (16) Brauer, G., Ed. Handbuch der Praparativen Anorganischen Chemie, Vol. 2, 3rd ed.; Friedrich Enke: Stuttgart, 1978; p 630. (17) Brauer, G., Ed. Handbuch der Praparativen Anorganischen Chemie, Vol. 2, 3rd ed.; Friedrich Enke: Stuttgart, 1978; p 632. (18) Brauer, G., Ed. Handbuch der Praparativen Anorganischen Chemie, Vol. 2, 3rd ed.; Friedrich Enke: Stuttgart, 1978; p 628. (19) Jacobs, J.; McGrady, G. S.; Willner, H.; Christen, D.; Oberhammer, H.; Zylka, P. J. Mol. Struct. 1991, 245, 275. (20) Edgell, W. F.; Potter, R. M. J. Chem. Phys. 1956, 24, 80. (21) Burger, H; Pawelke, G. J. Chem. Soc., Chem. Commun. 1988, 105. (22) Andrews, L.; Johnson, G. L. J. Phys. Chem. 1984, 88, 425. (23) Schurvell, H. F.; Faniran, J. A. J. Mol. Spectrosc. 1970, 33, 436.
Exciplex and Charge-Transfer Complex Fluorescence in the Inter- and Intramolecular Jet-Cooled EDA Systems Noriyuki Kizu and'Michiya Itoh* Faculty of Pharmaceutical Sciences, Kanazawa University, Takara-machi, Kanazawa 920, Japan (Received: January 16, 1992; In Final Form: March 9, 1992) The exciplex fluorescence was observed in the excitation of the van der Waals complex between 9,lO-dicyanoanthracene and naphthalene in supersonicexpansion,where no signifcant vibrational energy dependence was observed in the transformation of the complex to the exciplex. In the jet-cooled intramolecular EDA system of (9,10dicyano-2-anthryl)(CHz)3( I-naphthyl), very broad excitation and diffuse red-shifted fluorescence spectra were observed. The red-shifted fluorescenceof the jet-cooled intramolecular EDA system seems attributable to the emission of the intramolecularly interacted charge-transfer state formed in the ground state. In inter- and intramolecular systems of 9-cyano-IO-methylanthracene/naphthalene and (9-cyano-10anthryl)(CHz)s(2-naphthyl), neither vdW complex nor charge-transfer interaction was detected in both the ground and excited states.
