Theoretica l Study on Effect of Tetraz ine Structures on The ir Therma l D ecom position M echan ism s

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1 Ch inese Journa l of Explosives & Propellan ts 1,,,,, (, ) :, 5, B 3L YPg62311G (d, p ),,,,, 5, ;, : ; ; ; ; ; : TJ 55; TQ 2528: A : (2008) Theoretica l Study on Effect of Tetraz ine Structures on The ir Therma l D ecom position M echan ism s X ION G Y ing, SHU Yuan2jie, WAN G X in2feng, ZON G H e2hou, ZHOU Yang, Y IN M ing ( In stitu te of Chem icalm aterials, CA EP, M ianyang Sichuan , Ch ina) Abstract: T he therm al decompo sition trajecto ries of s2tetrazine mo lecule and its five derivatives w ere sim ulated by ab initio mo lecular dynam ics (A IM D ) m ethod to acquire the po ssible decompo sition pathw ays and identify their relative impo rtance. T he reaction channels w ere studied by density functional theo ry (D FT ) at B 3L YPg62311G (d, p ) level to locate the local m inim um po ints and the transition structures, and to verify the result of A IM D in term s of energy, suggesting that s2tetrazine m o lecu le underw en t concerted trip le dissociation, ju st as its pho to lysis m echanism. T he effect rules of five different substituents on the modes of tetrazine ring opening, the stability of the tetrazine ring and therm al decompo sition m echanism of tetrazine derivatives w ere obtained. If the stability of the sub stituen t is better than that of the tetrazine ring, decom po sition occu rs first th rough the ring b reak ing. O therw ise, the sub stituen t reaction s first take p lace. M o reover, som e new conclu sion s abou t the effect of intermo lecular reaction on the therm al decompo sition m echanism s of tetrazines w ere ach ieved. Key words: physical chem istry; tetrazine; h igh n itrogen; therm al decom po sition m echan ism; den sity functional theo ry; ab initio mo lecular dynam ics,,,, Zhang Jun [ 1 ], 3, 62 21, 2, 4, 52 : (1) : ; : : 2N SA F ( ) : (1978- ),,,

2 N 2, N - N ; (2), 3, 62 21, 2, 4, 52, S. Lo bbecke [ 2 ] :,,, 3, 62 21, 2, 4, 52,, 75%,, (T ), 5, 1 5 : 3, 622 1, 2, 4, 52 (DA T ) 3, 6221, 2, 4, 52 (DH T ) 3, 62 21, 2, 4, 52 (D ia T ) 3, 62 ( ) 21, 2, 4, 52 (BTA T z) 3, 3 2(62 21, 2, 4, 52 ) (DAA T ), 1 1 F ig. 1 T he structural fo rm ula of several tetrazine com pounds VA SP [ 326 ], 6,, Bo rn2oppenheim er, Perdeq2W ang, eV VA SP N H C V anderb ilt 0. 5 fs Gau ssian03 [ 7 ] B 3L YPg62311G (d, p ),, (NBO ) , ( nm ),, T S, T able 1 Comparison of the tetrazine ring opening modes in the six tetrazine compounds (T )R T H D 2h DA T N H 2 C 2h g(kj mo l - 1 ) DH T N HN H 2 C D ia T N 3 C 2h BTA T z C 2h DAA T N H 2, C : DH T, 1, (T ), 1 N 2 2 HCN [ 8 ], [ 9215 ], Sharm ila V. [ ] DA T D ia T, DH T BTA T z, C- N 1 N 2 DAA T, - N H 2 C- N

3 31 1,,, : 3,,,,, 6, 1, H, ΠΠ ( 2 ),, ( 3 ),, kj gm o l 2 ( 4. 2 kjgmo l) F ig. 2 Part second2o rder stabilization interaction energy betw een the ring and the substituents ( 4. 2 kjgmo l) 3 5 F ig. 3 T he delocalized mo lecular o rbitals of the five tetrazine derivatives 2. 2, B 3L YPg62311G (d, p ) 2 5 D ia T, H, H DH T, [ 18 ] D ia T CN - NN N 2, HN 3 [ 18 ],, C - N, D ia T BTA T z, ( [ ] ), N H - N, HN 3,, kj gm o l N H - N,,, 3, N - N N 2, N H - N, N 2, kj gm o l,, N H - N, BTA T z,, BTA T z DAA T, N - C, N HN H N - H, (T ) R HR,, HR, 2 5 T able 2 R eaction pathw ays of substituents in five tetrazine derivatives g g% (kj mo l - 1 ) DA T DH T DH T DH T D ia T CN - NN BTA T z N H - N BTA T z HN DAA T C- N ( 1 ) ( 2 ), DA T DH T DAA T, D ia T BTA T z

4 4 31 1, 4, ;,, Zhang [ 1 ] S. Lo bbecke [ 2 ],,, 4 F ig. 4 T he tw o decompo sition modes of tetrazines 2. 4,DH T kjgm o l, DA T kj gm o l, DH T 164, DA T 200 [ 1 ],, DH T, - NN H 3 ( 5 ) kj gm o l, DH T 115kJ gm o l, 70 kjgm o l, N H 3 N 2 (104 kj gm o l) 5 DH T (, kjgmo l) F ig. 5 T he channel and energy barriers of DH T intermo lecular reaction (co rrected by the zero2po int energies, in kjgmo l), DH T ΠΠ,,, (3) DH T DA T ( H ) (T )R HR, (4), 3 (1) 3,, (2), ;, (5) DH T,, N H 3,, DH T

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