“…N 4 . Although there have been many theoretical studies of tetrahedral 1a and four-membered cyclic 1b during the past 25 years, − ,− some interesting unresolved problems deserve more precise investigation.…”
Section: Resultsmentioning
confidence: 99%
“…As this may be important in the chemistry of N 4 , ,, open-chain triplet forms were investigated in more detail. The C 2 h open-chain triplet minimum ( 1f ), recently characterized at the MP4SDTQ//MBPT(2)/6-31G* level, was considered to be the lowest chemically bound N 4 isomer …”
Section: Resultsmentioning
confidence: 99%
“…Tetraazatetrahedrane ( 1a ) and its isomeric forms, e.g. tetraazete (tetraazacyclobutadiene, 1b ), have been studied extensively by theoretical methods. − Many theoretical efforts to elucidate the properties of this experimentally unknown species have been stimulated by the potential application of N 4 as a “pure” high-energy density material (HEDM) 2,3 and by the fundamental significance of N 4 with regard to chemical concepts, such as bond energy, ring strain, and aromaticity . A metastable molecule (local minimum on a PES) might be a candidate for HEDM, if considerable energy is released in conversion to the stable form per mass unit (the amount of stored energy) and if the energy barrier between the metastable form and the stable products is high.…”
The energies and structures of the 28-electron tetraatomic molecules, composed of the first row nonmetallic elements: N 4 (1), CN 2 O (2), BFN 2 (3), C 2 O 2 (4), B 2 F 2 (5), CBFO (6), C 2 FN (7), and BNO 2 (8) have been studied uniformly by ab initio methods including coupled-cluster theory. New estimates of the stability of the N 4 isomers, tetraazatetrahedrane and tetraazacyclobutadiene, are presented, and a new triplet NNNN openchain isomer has been established computationally. Potential energy surfaces of the nonpolar 1 and the polar 2 are compared. Three-membered cyclic C 2V fluorodiazaboririne has been found to be the most stable isomer similar to diazirinone (Chem. Phys. Lett. 1994, 227, 312). Linear triplet CO and BF dimers, OCCO, FBBF, and OCBF, are the most stable forms of 4, 5, and 6, respectively. The singlet cyanofluoromethylene, NCCF, the global energy minimum of 7, is 7 kcal/mol more stable than isomeric CNCF and 10 kcal/mol lower in energy than 3-fluoroazacycloprop-2-ylidene. The singlet and triplet forms of nitrosoboroxide, OBNO, the most stable isomers of 8, were found to have similar energies, within 1 kcal/mol, and the isomeric triplet OBON lies only 4 kcal/mol above OBNO. Singlet-triplet energy separations and dissociation energies to diatomic fragments are compared for the series of linear 14-and 14-electron (NNNN, NNCO, OCCO, FBBF, and OCBF) and open-chain 13-and 15-electron (NCNO, OBCF, NCCF, and OBNO) dimers. Trends in the chemical bonding in the series of 28-electron tetraatomic molecules, 1-8, stability, and possible synthetic routes, are discussed.
“…N 4 . Although there have been many theoretical studies of tetrahedral 1a and four-membered cyclic 1b during the past 25 years, − ,− some interesting unresolved problems deserve more precise investigation.…”
Section: Resultsmentioning
confidence: 99%
“…As this may be important in the chemistry of N 4 , ,, open-chain triplet forms were investigated in more detail. The C 2 h open-chain triplet minimum ( 1f ), recently characterized at the MP4SDTQ//MBPT(2)/6-31G* level, was considered to be the lowest chemically bound N 4 isomer …”
Section: Resultsmentioning
confidence: 99%
“…Tetraazatetrahedrane ( 1a ) and its isomeric forms, e.g. tetraazete (tetraazacyclobutadiene, 1b ), have been studied extensively by theoretical methods. − Many theoretical efforts to elucidate the properties of this experimentally unknown species have been stimulated by the potential application of N 4 as a “pure” high-energy density material (HEDM) 2,3 and by the fundamental significance of N 4 with regard to chemical concepts, such as bond energy, ring strain, and aromaticity . A metastable molecule (local minimum on a PES) might be a candidate for HEDM, if considerable energy is released in conversion to the stable form per mass unit (the amount of stored energy) and if the energy barrier between the metastable form and the stable products is high.…”
The energies and structures of the 28-electron tetraatomic molecules, composed of the first row nonmetallic elements: N 4 (1), CN 2 O (2), BFN 2 (3), C 2 O 2 (4), B 2 F 2 (5), CBFO (6), C 2 FN (7), and BNO 2 (8) have been studied uniformly by ab initio methods including coupled-cluster theory. New estimates of the stability of the N 4 isomers, tetraazatetrahedrane and tetraazacyclobutadiene, are presented, and a new triplet NNNN openchain isomer has been established computationally. Potential energy surfaces of the nonpolar 1 and the polar 2 are compared. Three-membered cyclic C 2V fluorodiazaboririne has been found to be the most stable isomer similar to diazirinone (Chem. Phys. Lett. 1994, 227, 312). Linear triplet CO and BF dimers, OCCO, FBBF, and OCBF, are the most stable forms of 4, 5, and 6, respectively. The singlet cyanofluoromethylene, NCCF, the global energy minimum of 7, is 7 kcal/mol more stable than isomeric CNCF and 10 kcal/mol lower in energy than 3-fluoroazacycloprop-2-ylidene. The singlet and triplet forms of nitrosoboroxide, OBNO, the most stable isomers of 8, were found to have similar energies, within 1 kcal/mol, and the isomeric triplet OBON lies only 4 kcal/mol above OBNO. Singlet-triplet energy separations and dissociation energies to diatomic fragments are compared for the series of linear 14-and 14-electron (NNNN, NNCO, OCCO, FBBF, and OCBF) and open-chain 13-and 15-electron (NCNO, OBCF, NCCF, and OBNO) dimers. Trends in the chemical bonding in the series of 28-electron tetraatomic molecules, 1-8, stability, and possible synthetic routes, are discussed.
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