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The investigation of reaction's ability of ferrocarbon crystal
ELSEVIER
Synthetic
The investigation
Metals 85 (1997)
1771-1772
of reaction’s ability of ferrocarbon
A.A.Ovchinnikov
crystal
. K.V.Bozhenko
Institute of Biochemical Physics of the Russian Academy of Sciences, Kosygin str., 4, Moscow 117334, Russia.
Abstract
In connection with the problem of radio waves absorption by the pyrolysis products of organic materials, ab initio calculations of complexes C4Hs*NaH, C4Hs*Na+ and Cz&.*NaH have been carried out with geometry optimization at UHF/6-31G* level. The molecular geometry of C4Hs was fixed and extracted from the structure of ferrocarbon crystal. Correlation corrections for heats of formation Q of thesecomplexeswere included by the second-and fourth-order MollerPlessetperturbation theory (MP2 and MP4). The comparisonof Q values for theseNa-containing complexeswith Q values for correspondingcomplexesC4Hs*LiH, C4Hs*Li+ and C&*Lii, obtained earlier at the samelevel, reveals the tendency to decreasingof Q values at substitution of Li atom by Na. The absenceof barriers for the addition reactions C4Hs + MH + C4Hs*MH , (M=Li or Na) has been shown in result of calculations of the potential curves for the decompositionreactions C4Hs*MH --+ C4Hs + MH at the UHF/6-31G* level. Key words:(Ab initio quantum chemicalmethodsand calculations)
1. Introduction
Possibility of presenceof light element complexes,e.g. with Li, Na, etc and their hydrides in the products of organic materials pyrolysis, was studied as being of a priority importance for radio wave absorption materials.* As the ferrocarbon crystal [l-4] can be consideredas such absorber, the complexesof Lii and Li+ with ferrocarbon crystal fragments and CtH2*LiH were calculated in [S]. Ab initio calculations [5] demonstratedthat generally Lll and Li+ can form complexeswith the fragments of ferrocarbon: C4Hs*LiH and C4Hs*Li+ , while the systemC3H6*Lii is not a complex. It hasbeen shown that differencesin geometric parametersof LiR in complexesCIHs*LiH and C2H2*Lii, obtained at the same level, are quite small. So small differences in the geometric parameters of Lii in these complexesdeserveattention, becausethe distancesbetween the radical centres in considered conformation of C4Hs (2.288A) and the carbon atomsin acetylene (1.185A) differ more than 1 A. Stability, conditioned by the possible presenceof any barriers, that can take place in course of decompositionreaction unfortunately has not been studied in work [5]. Besides, it is interesting to investigate the possibility of existence of such complexes, obtained at substitution of the Li atomsby Na. Ab initio calculationsof complexes C4Hs*NaH and C4Hs*Na+ were performed in this work. The complex C2H2*NaH, having an ordinary chemicalbond between carbon atoms, has been calculated * This work was supported by the International and Technology Center (Moscow) under the Grant 01.5 of 31.03.94 and by Russian Foundation for Fundamental Studiesunder the Grant 96-03-33905. 0379-5779/97/%17.00 0 1997Elsevier Science S.A All rightsreserved PII
SO379-6779(96)04584-5
at the samelevel to compare the geometric parametersand heats of formation Q of the complexes C4Hs*NaH and C4Hs*Na+ with onesof the complex C2Hz”Naf-I. At last the potential curves (PC) of decompositionreactions C4Hs*LiH
3
C4Hs + LiH
-3
C4Hs
(1)
and GHs*Nti
+ NaH
(4
have been calculated. All systemswere calculated in the singletground state. 2. Methods
The calculations were carried out on a CONVEX-C210 computer using program GAUSSIAN-82 by the unrestricted Hartree-Fock-Roothaan (UHF) method. Correlation corrections were included by the second- and Fourth-order Moller-Plessetperturbation theory with single, double-, triple-, and quadruple- excitations (MP2, MP4(SDQ), and MP4(SDTQ)). Standard split-valencebasis set 6-31G* was used. Calculations of the complexes GHs*NaH and C4Hs*Na+ were performed with the optimization of geometric parametersof the NaH molecule or Na+ relatively the atomsof C4Hs fragment at the UHF/631G* level. The moleculargeometry of C4H8 is similarto the geometry in [.5] and fixed. Complex C&*NaH has been calculatedwith full optimisation of geometry at the UHF/631G* level (as in [5]). The PC of reactions (1) and (2) have beencalculatedat the UHF/6-3lG* level. Each PC hasbeen
AA. Ovchinnikov, K.% Bozhenko/Synthetic Metals 85 (1997) 1771-l 772
1772
Tablel. Heats of formation Q of the complexesC4Hs*MH, C4Hs*M+ 3lG* basisset (kcalimol). UHF MP2
and Cz.&*MH (M=Li, Na), obtained at different levelswith 6MP4(SDQ)
MP4(SDTQ)
15.6
15.7
29.4
29.4
12.5
12.8
8.6
8.8
18.8
18.9
7.5
7.7
C4Hs*LiH 15.5
16.4
GHs*H+ 31.4
30.3
GHz*LiH 11.0
12.8 c&s*Na’fif
9.5
9.4 ChHs*Na+ 19.7
20.7
CzHz*NaH 7.0
7.8
calculatedfor fixed distancesbetweenM atom and radical centresin C4Hs (R) , changingfrom R. to R. +2.4 A, with interval 0.2 A (R. is equal to R for ground state of C4Hs*MH). All other geometric parameters of MH moleculeshave been optimized. The results of ab initio calculationsof Q valuesfor all consideredsystemsare listed in Table 1 (data for complexeswith Li have beentaken from [5] ), and PC for both reactionsare depictedin Fig. 1. 3. Results
The results of ab initio calculations testify to the fact that both systemsChHs*NaH and GHs*Na+ are the complexes.For instance,in caseof CdHs*NaH the distance betweenatoms in NaH moleculeis practically the same,as in the isolatedNaH molecule (the difference between them is 0.024A). 14
The geometricparametersof Na.H moleculeare very near to each other in the complexesCkHs*NaH and CzJ%*NaH. For example, the R in the first complex (2.986 A) only is 0.038 A shorter then R in the secondcomplex (3.024 A). For CdHs*Na+R=2.866 A Thus, in can be expected that when MH molecules form the complexes with carbon compounds,which have the distancesbetween the carbon atoms, coordinating MH, from -1.2 A to -2.2 A, the geometric parameters of MIX are as in considered complexes.It can be seenfrom Table 1) that variations of Q values on passingfrom the UHF to the MP2 and MP4 methods are not more, than 2 kcal/mol. Then, within all usedapproximations,the following inequalitiesare fulfilled: Q(O,HZ*L~H) < Q(CdHs*LiH) < Q(GHs*Li+) and Q(CZb*NaH) C Q(C4Hs”NaH) C Q(ChHe*Na+).However, ChHs*M+ complexescan exist only in the absenceof H-, becausethe formation of C4Hs*MTI from GHs*M* and His energetically favourable. Besides,the next relations are fulfilled: Q(GHs*Na+)
References
I
0.0
0.4
I
0.8
I
1.2
I
1.6
I
2.0
R-b SAI Fig. 1. PC for reactions (1) and (2).
2.4
[l] A.A.Ovchinnikov and V.N.Spector, In Saegusa, T.Higashimuraand A.Abe (Eds), Frontiers of Macromolecular Science,IUPAC, Blackwell Scientific Publications, 1989,455. [2] A.A.Ovchinnikov and V.N.Spector, Synth. Metals, 27 (1988)B615. [3] A.A.Ovchinnikov and I.L.Shamovsky, J.Mol.Struct. (Theochem),251(1991)133. [4] A.A.Ovchinnikov, I.L.Shamovsky and K.V.Bozhenko, J.Mol.Struct. (Theochem),251(1991)141. [5] A.A.Ovchinnikov and K.V.Bozhenko, Doklady Akademii Nauk, 346(996) 63.
Synthetic
The investigation
Metals 85 (1997)
1771-1772
of reaction’s ability of ferrocarbon
A.A.Ovchinnikov
crystal
. K.V.Bozhenko
Institute of Biochemical Physics of the Russian Academy of Sciences, Kosygin str., 4, Moscow 117334, Russia.
Abstract
In connection with the problem of radio waves absorption by the pyrolysis products of organic materials, ab initio calculations of complexes C4Hs*NaH, C4Hs*Na+ and Cz&.*NaH have been carried out with geometry optimization at UHF/6-31G* level. The molecular geometry of C4Hs was fixed and extracted from the structure of ferrocarbon crystal. Correlation corrections for heats of formation Q of thesecomplexeswere included by the second-and fourth-order MollerPlessetperturbation theory (MP2 and MP4). The comparisonof Q values for theseNa-containing complexeswith Q values for correspondingcomplexesC4Hs*LiH, C4Hs*Li+ and C&*Lii, obtained earlier at the samelevel, reveals the tendency to decreasingof Q values at substitution of Li atom by Na. The absenceof barriers for the addition reactions C4Hs + MH + C4Hs*MH , (M=Li or Na) has been shown in result of calculations of the potential curves for the decompositionreactions C4Hs*MH --+ C4Hs + MH at the UHF/6-31G* level. Key words:(Ab initio quantum chemicalmethodsand calculations)
1. Introduction
Possibility of presenceof light element complexes,e.g. with Li, Na, etc and their hydrides in the products of organic materials pyrolysis, was studied as being of a priority importance for radio wave absorption materials.* As the ferrocarbon crystal [l-4] can be consideredas such absorber, the complexesof Lii and Li+ with ferrocarbon crystal fragments and CtH2*LiH were calculated in [S]. Ab initio calculations [5] demonstratedthat generally Lll and Li+ can form complexeswith the fragments of ferrocarbon: C4Hs*LiH and C4Hs*Li+ , while the systemC3H6*Lii is not a complex. It hasbeen shown that differencesin geometric parametersof LiR in complexesCIHs*LiH and C2H2*Lii, obtained at the same level, are quite small. So small differences in the geometric parameters of Lii in these complexesdeserveattention, becausethe distancesbetween the radical centres in considered conformation of C4Hs (2.288A) and the carbon atomsin acetylene (1.185A) differ more than 1 A. Stability, conditioned by the possible presenceof any barriers, that can take place in course of decompositionreaction unfortunately has not been studied in work [5]. Besides, it is interesting to investigate the possibility of existence of such complexes, obtained at substitution of the Li atomsby Na. Ab initio calculationsof complexes C4Hs*NaH and C4Hs*Na+ were performed in this work. The complex C2H2*NaH, having an ordinary chemicalbond between carbon atoms, has been calculated * This work was supported by the International and Technology Center (Moscow) under the Grant 01.5 of 31.03.94 and by Russian Foundation for Fundamental Studiesunder the Grant 96-03-33905. 0379-5779/97/%17.00 0 1997Elsevier Science S.A All rightsreserved PII
SO379-6779(96)04584-5
at the samelevel to compare the geometric parametersand heats of formation Q of the complexes C4Hs*NaH and C4Hs*Na+ with onesof the complex C2Hz”Naf-I. At last the potential curves (PC) of decompositionreactions C4Hs*LiH
3
C4Hs + LiH
-3
C4Hs
(1)
and GHs*Nti
+ NaH
(4
have been calculated. All systemswere calculated in the singletground state. 2. Methods
The calculations were carried out on a CONVEX-C210 computer using program GAUSSIAN-82 by the unrestricted Hartree-Fock-Roothaan (UHF) method. Correlation corrections were included by the second- and Fourth-order Moller-Plessetperturbation theory with single, double-, triple-, and quadruple- excitations (MP2, MP4(SDQ), and MP4(SDTQ)). Standard split-valencebasis set 6-31G* was used. Calculations of the complexes GHs*NaH and C4Hs*Na+ were performed with the optimization of geometric parametersof the NaH molecule or Na+ relatively the atomsof C4Hs fragment at the UHF/631G* level. The moleculargeometry of C4H8 is similarto the geometry in [.5] and fixed. Complex C&*NaH has been calculatedwith full optimisation of geometry at the UHF/631G* level (as in [5]). The PC of reactions (1) and (2) have beencalculatedat the UHF/6-3lG* level. Each PC hasbeen
AA. Ovchinnikov, K.% Bozhenko/Synthetic Metals 85 (1997) 1771-l 772
1772
Tablel. Heats of formation Q of the complexesC4Hs*MH, C4Hs*M+ 3lG* basisset (kcalimol). UHF MP2
and Cz.&*MH (M=Li, Na), obtained at different levelswith 6MP4(SDQ)
MP4(SDTQ)
15.6
15.7
29.4
29.4
12.5
12.8
8.6
8.8
18.8
18.9
7.5
7.7
C4Hs*LiH 15.5
16.4
GHs*H+ 31.4
30.3
GHz*LiH 11.0
12.8 c&s*Na’fif
9.5
9.4 ChHs*Na+ 19.7
20.7
CzHz*NaH 7.0
7.8
calculatedfor fixed distancesbetweenM atom and radical centresin C4Hs (R) , changingfrom R. to R. +2.4 A, with interval 0.2 A (R. is equal to R for ground state of C4Hs*MH). All other geometric parameters of MH moleculeshave been optimized. The results of ab initio calculationsof Q valuesfor all consideredsystemsare listed in Table 1 (data for complexeswith Li have beentaken from [5] ), and PC for both reactionsare depictedin Fig. 1. 3. Results
The results of ab initio calculations testify to the fact that both systemsChHs*NaH and GHs*Na+ are the complexes.For instance,in caseof CdHs*NaH the distance betweenatoms in NaH moleculeis practically the same,as in the isolatedNaH molecule (the difference between them is 0.024A). 14
The geometricparametersof Na.H moleculeare very near to each other in the complexesCkHs*NaH and CzJ%*NaH. For example, the R in the first complex (2.986 A) only is 0.038 A shorter then R in the secondcomplex (3.024 A). For CdHs*Na+R=2.866 A Thus, in can be expected that when MH molecules form the complexes with carbon compounds,which have the distancesbetween the carbon atoms, coordinating MH, from -1.2 A to -2.2 A, the geometric parameters of MIX are as in considered complexes.It can be seenfrom Table 1) that variations of Q values on passingfrom the UHF to the MP2 and MP4 methods are not more, than 2 kcal/mol. Then, within all usedapproximations,the following inequalitiesare fulfilled: Q(O,HZ*L~H) < Q(CdHs*LiH) < Q(GHs*Li+) and Q(CZb*NaH) C Q(C4Hs”NaH) C Q(ChHe*Na+).However, ChHs*M+ complexescan exist only in the absenceof H-, becausethe formation of C4Hs*MTI from GHs*M* and His energetically favourable. Besides,the next relations are fulfilled: Q(GHs*Na+)
References
I
0.0
0.4
I
0.8
I
1.2
I
1.6
I
2.0
R-b SAI Fig. 1. PC for reactions (1) and (2).
2.4
[l] A.A.Ovchinnikov and V.N.Spector, In Saegusa, T.Higashimuraand A.Abe (Eds), Frontiers of Macromolecular Science,IUPAC, Blackwell Scientific Publications, 1989,455. [2] A.A.Ovchinnikov and V.N.Spector, Synth. Metals, 27 (1988)B615. [3] A.A.Ovchinnikov and I.L.Shamovsky, J.Mol.Struct. (Theochem),251(1991)133. [4] A.A.Ovchinnikov, I.L.Shamovsky and K.V.Bozhenko, J.Mol.Struct. (Theochem),251(1991)141. [5] A.A.Ovchinnikov and K.V.Bozhenko, Doklady Akademii Nauk, 346(996) 63.