Theoretical study on the structures of boron–nitrogen alternant open chain compounds Jianguo Zhang, Qian Shu Li * , Shaowen Zhang The State Key Laboratory of Prevention and Control of Explosion Disasters, School of Science Beijing Institute of Technology, Beijing 100081, People’s Republic of China Received 13 July 2004; accepted 24 September 2004 Available online 21 December 2004 Abstract The Hartree–Fock HF/cc-pVDZ method, the density functional theory B3LYP/cc-pVDZ method and the Møller–Plesset MP2/cc-pVDZ method are employed to optimize the structures of a series of boron–nitrogen alternant open-chain compounds and their isomers. The results show that all the three methods can obtain reasonable structures. The relative stabilities of the isomers are compared based on the energies refined at the CCSD (T)/cc-pVTZ level of theory. The electronic properties of these compounds are also discussed. q 2004 Elsevier B.V. All rights reserved. Keywords: Boron; Nitrogen; Aminoborane; Open chain compounds; Ab initio; DFT method 1. Introduction Recently, the boron–nitrogen compounds have drawn the attention [1–14] of scientists due to their promising future in many applications, such as in the fields of conducting- polymers [15–17], the chemical vapor deposition (CVD) [18–22], the fuel cell and the hydrogen storage [23–26]. So far, due to its importance as a basic unit for complex aminoborane, most studies about boron–nitrogen com- pounds are concentrated on aminoborane, H 2 BNH 2 , the B–N analogue of ethylene. Besides the extensive experimental studies [27–31] on the determination of structure, detection of physical properties and reaction mechanism with other compounds, some theoretical investigations [32–36] were also carried out for H 2 BNH 2 . McKee [32] reported an ab initio study of the formation of H 2 BNH 2 from the reaction of B 2 H 6 with NH 3 through 1,2 di-hydrogen elimination at the MP2/6-31G(d) level of theory. Ha [33] presented the results of ab initio SCF/6-31G** calculations for the aminoborane, diaminoborane and aminodifluoroborane. Then, Minyaev [34] and Mo [35] reported the reaction paths and the theoretical analysis for the internal rotation in aminoborane with difference method of theories, respect- ively. Recently, Suresh [11] studied the conjugation involving nitrogen lone-pair electrons of some boron– nitrogen compounds with B3LYP/6-31G(d) level of theory. In 2001, Kiran [9] compared the parallel behavior between hydrocarbons and corresponding boron–nitrogen analogues at B3LYP/6-311CG** level and suggested that the protonation and methylation of boron–nitrogen compounds were coincident with corresponding hydrocarbons. How- ever, knowledge about the structures and electronic properties of boron–nitrogen chain compounds are still quite limited. In the present study, we provide a systematic calculation on the structures and some electronic properties of smaller boron–nitrogen alternant open-chain compounds and their isomers (H 2 BNH 2 ,H 2 BNHBH 2 ,H 2 NBHNH 2 , H 2 BNHBHNH 2 ,H 2 BHNBHNHBH 2 and H 2 NBHNHBHNH 2 ). 2. Computational methods In order to acquire reliable structures, we employ three sophisticated methods to optimize the geometries, namely, 0166-1280/$ - see front matter q 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.theochem.2004.09.062 Journal of Molecular Structure: THEOCHEM 715 (2005) 133–141 www.elsevier.com/locate/theochem * Corresponding author. Tel./fax: C86 10 68912665. E-mail address: qsli@bit.edu.cn (Q.S. Li).