spectral and energy data for bis (polyfluoro-aryl) amine ... · bis (polyfluoro-aryl) amine...

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Spectral and Energy Data forBis (Polyfluoro-Aryl) AmineComplexes with HydrogenNH…B BondV. E. Borisenko a , E. V. Maximov a , G. S. Denisov b ,G. G. Furin c & Ju. A. Zavjalova aa Physics Faculty, Tyumen State University, Tyumen,625000, Russiab Institute of Physics, St. Petersburg StateUniversity, St. Petersburg, 198904, Russiac Novosibirsk Institute of Organic Chemistry,Novosibirsk, 680090, Russia

Available online: 23 Sep 2006

To cite this article: V. E. Borisenko, E. V. Maximov, G. S. Denisov, G. G. Furin & Ju. A.Zavjalova (1993): Spectral and Energy Data for Bis (Polyfluoro-Aryl) Amine Complexeswith Hydrogen NH…B Bond, Spectroscopy Letters, 26:6, 1139-1151

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SPECTROSCOPY LETTERS, 26(6), 1139-1151 (1993)

SPECTRAL AND ENERGY DATA FOR BIS ( POLYFLUORO-ARYL) MINE COMPLEXES WITH HYDROGEN N H . . . B BOND

Key Words: IR spectroscopy, hydrogen bond, bis ( volyfluoro-aryl) amine, enthalpy of hydrogen bonds

* 8 .I V.E.Borisenko , 2. V.Maximv , G . S . D e n i s o v

G.G.Furin , Ju.A.Zavjalova 1.1. 8

* Physics Faculty, Tyumen State University, Tyumen 625000, R u s s i a

% 8 Institute of Physics, St.Petersburg State University, St. Petersburg 198904, Russia

Novosibirsk Institute of Organic Chemistry, Novosibirsk 680090, Russia

ABSTRACT In the I R spectra of complexes of (C6PslzNtl,

I 4-CP,C6F4 ),NH and ( y-NC5Pq ),NH with acetonitrile, tetrahydrofurane, dimethylformamide, dimethylsulfoxide and hexametapole, the u ( N H ) band has a complex structure due to Fermi resonance with lowfrequency

1139

Copyright 0 1993 by Marcel Dekker, Inc.

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1140 BORISENKO ET AL.

vibration combinations. In the range of 15-65OC the equilibrium constants and compiex formation enthalpies in CCI, solution have been determined.

RODUCT I ON Secondary amines of %NH type, where R is the

polyfluorinated aryl radical, are potentially strong W a c i d s and are therefore a prospective object ror investigating the hydrogen bond NH... B. Increased acidity of amines with pentafluorphenyl rings is demonstrated by the data on the equilibrium NH-acidity in DMSO (9-phenylfluorene as standard, pK + 18.5,

( C , F , ) , N H 12.6 and counterion K + I : C6F5NHC5F4N 9.4 lg units . The acidifying effect of the polyfluoroaryl fragment has been shown to depend on the substituents, as shown by pK

2,3,5,6- tetraf luoropyridyl group ( pK decreases by 3.9 lg units) and by the effect of R aubatituent in para-position of tetraf luorophenyl group ( 8 . E . , pK varies in the series of R substituenta: --P-CF3-CN as follows:13.6- 12.6- 10.6- 9.1) .

The data on the proton-donating ability of 8uch compounds in complexes with typical proton acceptors, on the possibility and conditions of proton transfer over the hydrogen bond, on the shape of the band. VINH...B) in vibrational spectrum m u s t be useful both for better understanding of the energetics and spectral manifestations of a strong NH... B bond ard for characterizing the intermolecular interactions of fluoroaromatic amines which represent a new class of protonodonors.

c6=5NHz 123*1,

measurements on passing from '6 ' 5 to

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BIS (POLYFLUORO-ARYL) AMINE COMPLEXES 1141

For that purpose we have studied spectral and

thermodynamic data f o r the complexes of secondary

I r-NC5F4 12NH ( 111 1 with acceptors: acetonitrile, tetrahydrofurane, dirnet.hylformamide, dimethylsulfoxide and hexametapoie in CCI, solution.

amine6 (c6F5 ),NH ( I) P ( 4-cFsc6Fq ),NH ( 11) and

EZCPERTMENTAL The compounds 1-111 were synthesized according to

2 - 1 . The IR spectra in the range of 2400-3600 em were

obtained on a Specord IR 75 Carl Zeiss. Jena instrument. The measurements were carried out in the temperature range 15-65OC with an accuracy of A 1 C. The spectral moments of bands were found by numerical integration wit‘n an accuracy for free molecule bands being 1-2 cm-I, for bands of complexes 3-5 cm-’. The integrai intensities of absorption bands were measured using planimetry in coordinates A, uc with an accuracy of about 7-10 %.

0

RESULTS DISCUSSION The spectra of CCI4 solutions of compounds I-IIi

show an intense single band in the range of vINH), which corresponds to monomer amine molecules; the parameters of the band are given in Tab.1. In the using range of concentrations C < 0.02 rnol/dm , no evidence of self-association of amines is found. Increased temperature of solution results in the high-frequency shift of the band vlIH), its slight broadening and decreased integrated iritensi ty. In the range of 15-65OC these parameters change approximately linearly. The temperature variations of frequency and width of the band u(NH1 of amines 1-111 are of about

3 ”.-

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34 16

=i27l 3148 3130 3101

2961 3412

3197 30 69

3037 3003 2634 3407 3165

3030 2978

2947 2825

2a*

186

267 280 263 314

29*

238 289

3 25 3 10 366 31*

26 I 30 1 348 357 364

13

37 58 75

79 98 16 60 99 105 116 132 16 62 88 122 136 140

t Band ha1 f wid th Au I, ( NH 1

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t h e s a m e order of magnitude as f o r a l c o h o l s and phenols

In t h e p re sence of a p ro ton a c c e p t o r B, t h e

i n t e n s i t y of t h e band v(NH) d e c r e a s e s and a new wide band appea r s w i i i c . t i is s h i r Led Lclwar- t is l o w f r e q u e n c i e s and helongs t,cl hydrogen bond N i - l . . .B complexes, Fig.1-3. T h e band has a clear-cut s t r u c t u r e which

s p e c i f i c a l l y changes for s t r o n g e r hydrogen bonds and greater low f requericy s h i f t s . For complexes w i t h a s t r o n g botid Lhe band c o n s i s t s of up t o 10-15 coinponer1t.s. O n e cari observe i n Fig. 1-3 s e q u e n t i a i i nc rease of i r i k r i s i ties of tiin l o w f r e q u e n c y components of i,ne w i d e band v ( iVH) w i i . h increase of the

proton-accept ing ahi Z i t y o f B . I*lany components r e t a i n t h e i r p o s i t i o n i n Lhw f requency scale. Some components are a l s o observeti as v e r y w e a k bands i n t h e spec t rum of free amine inolecules . A s the. Land's c e n t e r o f

gravity shi f t . s i . . T > 'i ow f reqcirricies, t.he hi&-frequenc:y components pass Lhrwuyli the iniaris i t y maximum to

become weaker. Siich x behavior is t y p i c a l of

Fermi-resonant s t r - u c txre of barids OF hydrogen bond complexes. I t s e r v e s as a c r i t e r i o n t o e x p l a i n t h e o r i g i n of a s.tructtira clue t o Fermi resonance of v i b r a t i o n u l Ah') w.i L h overtorigs and combination t o n e s of l o w f r e q u e n c y vii,rili..ions. k similar hehavior of the band u l W i l is c.~i)sts'.rvc?J, for exxainpla, i r i t h e s p e c t r a of

imidazole complexes with various proton a c c e p t o r s . Comparing tine spect.ra of arnine I- I I I complexes, one can notice 'a ( : t ? r * h i r i s i m i 1 a r . i t . y i n the: band f o r m of

these cpmplaxas. T h i s is n a t u r a l l y expla ined by the similari ty of f I - + q ! J ~ I i C i ~ s of i<i\LTfr.equency v i b r a t i o n s irkeractiI1g NJi i..h p i iv'iii i ! I the iaoirculas of simiiar s t r u c t . u r e I- T T I . Tiir ireqiiarw:.irts of these vibrations

5 ,pyrrole and indol . 3,4

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E U z

- 1

2600 3000 3400 ' r CJn

Fig.1. The absorption bancis ~ ( I u ' h ' ) of the compound

( C6F5 IplFi i 11 i n 'ri-bonded complexes with different proton acceptors in C C l l t . i Conceiitrations of compounds

in solution noted in brackets , M dm 1: ( 1 ) ( O . O i 2 ) ; 2; ( 1 ) i0.0151+CH3CN (0.3); 3: ( 1 ) (0.0141+(CD2I40 i0 .261;

4: [ 11 (0.021+DCCOI?( CD3 l 2 t 0.05); 5: ( 1 ) (0.02)+(CH3),S0 ( 0 . 0 4 ) ; 6: ( 1 ) (0.07)+[(CDg)2J+13iJG (0.100).

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2600 3000 3400 p , cm

F i g . 2 . The absorption bands v(NH) of t h e compound ( 4-CF,C,F4),NH ( 11) in H-bonded complexes w i t h d i f f e r e n t proton acceptors i n CCl,.

1: 1 2 ) (0.0i); 2: ( 2 ) (0.02)+CH3CN (0.351; 3: I21 10.012)+ICD2)q0 (0.35);

5: f 2) ( 0.02)+(CH3 ) 2 S 0 (0.02); 6: (2) (0.066)+[(CD3)pr'lJQP0 (0.100).

4: ( 2 ) (0.02)+Dcc01~(cD& (0.07;;

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F i g . 3 . The absorption bands v ( W I of the compound (r-NC5F4 ) 2 N H ( I11 1 i n Ii-bonded complexes w i t h d i f f e r e n t proton acceptors in CClq.

1: ( 3 ) (0 .012) ; 2: ( 3 1 (0.02)+CX3CN ( 0 . 4 ) ;

3: ( 3 1 (0.03i+(CD21,0 IG.23); 4: ( 3 ) 0.02 )+DCCON( CD, l 2 0.0s 1 ;

5 : ( 3 ) (0.02)+(CH3),S0 i 0 . 0 5 ) ; 6: ( 3 1 ( 0.069 ) + I ( CD3 )2N1,P0 ( 0.100).

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remain a l i n r i s t i 2 o r i s t . x r i i i r i the suries of complexes, i.e. they (10 riot. dapenci on the strength of the hydrogen bonci W i i . . . "b .

Table i lis1.s the v a l u e s of band moments uf

complexes: the 7 ' C I ' C J moment M, ( integrated intensity) , the first moment M, (center of gravity of the band) and the second central moment % characterizing the band width. The effective half-width is related to the second moment as follows: A V ~ , ~ = ~ 4 ' ~ . It is seen from these data that in the series of proton acceptors, the lowfrequency shift of the band's center of gravity, its integrated intensity and, with some exceptions, effective half-wid th increase successively with the strength of hydrogen bond for all three amines. The lowfrequency shift reaches 400-500 cm , the half-width 350-400 cri-', the integrated intensity increases by almost an order, exceeding 10 d m /mol cm . All this is typical for the strongest complexes of NH donors and the values considerably exceed t h e corresponding parameters for the non-fluorinated amines

The radical C6Fs has a high electro-negativity and the positive charge on NH hydrogen greatly increases due to electron density shift towards the rings. However, the acidity of this group in compounds 1-111 is still insufficient for proton transfer to aliphatic amines in C6HI4 or CCl, solutions. A s shown by the UV and IR spectra, no ionic forms of compounds 1-111 are formed in excess of dibutylamine or tributylamine in these solvents.

At higher temperatures the band's center of gravity is shifted to higher frequencies , the effective half-width increases and the integrated

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5 3 2

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intensity decreases. These changes are greater by about an order than f o r the band u(NH) of free molecules, the relative change of integrated intensity being several times as great. The character of temperature dependence of M, and 4 is in qualitative agreement with the cannlusions of r e f s . which estimated the contribution to MI and M2 of the hot and sum- and difference- transitions with participation of l ow f requency vibrations of the complex.

Thermodynamic characteristics of the complexes, equilibrium constants K=[ AB I / [A ] I B 1 and enthalpies AH were measured by the intensity of the band Y ( N H ) of free molecules i n the presence of an acceptor at four. or five temperatures i n t,he range of 288-338 K.After graphical separation of this band from the band of the complexes its integrated intensity was measured and the concentratioii of free molecules of the proton donor I A 1 was c2aic:irl ated. The concentrations of

complexes [ARl arid Tree molecules of acceptor (B1 were calculated u s i n g halance equations for the proton donor [ A, 1-1 AB I + [ A 1 and acceptor [ B, I = [ A B I+[ B I . The calculations were a1 lowed f o r temperature dependence of solvent density and absorption coefficient of the band v ( N H ) . The enthaipy value w a s calculated from Vanthoff formula. The results are given in Tab.2. For complexes with hexametapole the Table gives only estimates. The nalcuiation of enthalpy using the correlnt ion dependence between enthalpy and integrated intensity increment of the band u(NH) on hydrogen bonding gives similar results varying within 10% in both directions.

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TABLE 2

Equilibrium constants K anci enthalpies - A H of complexes of f 1uorina.ted amines 1-111 with acceptors

- A H f kcal M - l

I__-----------------

3 - 1 Pro ton K z S o f d m 13

acceptor x 11 T I 1 T IT I11 CH3CN , 4 . 5 15 24 2.9 4 . 1 4 . 5

( C D 2 ) , 0 9.0 18 32 3.7 5.1 5.2 DCCON CD3 l2 37 i 60 520 4.3 5 . 7 6.8

( C H 3 ) , S 0 76 4 15 9.10 4.6 7.0 7.9 [ ( CD3 ) p I 3 P O -8 " 9 " 10

It is seen r'roa Tab.2 that the proton-donating ability of polyf iuorinated secondary arylarnines increases in the series I c 11 I T I ; changes in spectral parameters o f t'ne band v I N H ) are in agreement with changes in thermodynamic characteristics of the

complexes. Tho proton-donating ability of amines 1-111 is comparable to that of OH donors such as monochloroacetic acid, or trichlorophsnol.

Thus we have shown in this work t h a t polyfluoroaromatic arnines 1-111 are strong proton donors in the hydrogen bond. The v ( t W ) band of complexes with strong proton acceptors has a great width and a clear-cut structure resulting mainly from the Fermi-resonant interaction with l o w frequency vibration combinations. For quantitative description of this structure it is reasonable to investigate the form of U ( ND) bands in douterated donor complexes and to fulfill complete identification of vibrational spectrum.

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"1 1. Vlasov V.M., : e r . ech~va M . I . , P n t r o v E.S., Shatenstein A . T., Yakobson G.G. Equilibrvium NH acidity of pnl yf'loitroarnmatic compounds. Zhur. Org. Khim. GBSE. 19 : ; ; ; i 7 : 2G25-2G:ji .

2. Furin G.G. , ?I L l lei- A . 0 . , Ynkobson G. G. , Aromatic nucleophilic sii1Jst.i 1 c i t . i w n . XVIII. Reackiuns of polyf luoroaromai i t ; cornpowids with Na- and Li-

salts of hexameillyid is i l i jarnine. Tzv. SO A N SSSR, Ser . ~ t i i m i . r I . 1YCI.J; I? 1: 127-132. . C r ' r

3 . Schrems Q . , O b e r h o f f e r H . M . , Luck W . A . P . Hydrogen bonding in 1owt.emperature matrices. i . Proton donor abiiities of fluoroalcohols. J. Phys. Chem. 1984; 88: 43.75-4342.

4. Luck W . A . F . ~ Z r ~ r r i g K . Y . E f f e c t i>F s o i v e n t and temperature or'i 0J-i s t . t x tc? l i r'iy bands prortticeci by V a n der Waaia in te r*c . t , i c , r i . J. Chern. SOC. , Faraday Tr. 1984, Pt 2; 80 : 1255- i26R.

5 . Borisenko V.E., G r u s t i t r v a S . A . , Redina I . N . Temperature e f f e c t s cln itwio'le and p y r r u l e ul NH) absorption bards j r i FI-bonded curnplexes. 5. Molec. Liquids 1990; 45; iOi-107.

6. Wolff Ii., Muller H. Substructure of the NH stretching vibr.al.ivrib3 band of irnidazolc. J. Chem. Phys . 1974; 60: 29.76- 2939.

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7. Volff H., M u l l e r H. D i e Strukt i lr d e r NH-Valent- Schwingungsbande von Imidazol . Ber. Bunsenges. Phys. Chem. 1974; 78: 1241-1244.

8. Malarski Z . , Sobczyk 'L., Grech E. Structure and I R spec troscop ic iiahaviour of NHN hydrogen bonds. J. Molec. Struct . 1987; 177: 339-349.

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Marechal Y. A yuarititativs ana lys i s of the v g I R bands o f hydrogen bonds. Chem. Phys. 1963; 79: 89- 94.

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Date R e c e i v e d : December 30, 1992

Date A c c e p t e d : February 3 , 1993

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spectral and energy data for bis (polyfluoro-aryl) amine ... · bis (polyfluoro-aryl) amine...

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