title: Probing the influence of anomeric effects on the lithium ion affinity in 1,3-diaza systems: a computational study.
abstract: Lithium ion affinities of methanediamine (MDA), N,N,N',N'-tetramethylmethanediamine (TMMDA), 1,3-diazacyclohexane (DAC), trans-3,5-diazabicyclo[4.4.0]decane (trans-3,5-DBD), trans-1,3-diazabicyclo[4.4.0]decane (trans-1,3-DBD), cis-1,3-diazabicyclo[4.4.0]decane (cis-1,3-DBD), 1,5-diazabicyclo[3.3.1]nonane (DBN), trans-decahydro-8a,9a-diazaanthracene (trans-DDA), cis-decahydro-8a,9a-diazaanthracene (cis-DDA), 1,3-diazetidine (DAT), 1,3-imidazolidine (IMD), and 1,3-diazepane (DAP) have been studied by using density functional theory (DFT) and correlated ab initio methods. Possible conformers of these compounds were optimized at the B3LYP/6-31+G* level, and relative energies were evaluated at the MP2/6-311+G**//B3LYP/6-31+G* level. The experimental lithium ion affinities for reference molecules (i.e., ammonia and trimethylamine) are well-reproduced at these levels of theory. NBO analysis shows the influence of anomeric effects (n(N) → σ*(C-N) hyperconjugative interactions) on the conformational stability of the title compounds; however, the electrostatic and steric contributions included in the NBO Lewis term also affect the stabilities in some cases. The influence of anomeric effect is apparent in cis-DDA, where the nitrogen involved in n(N) → σ*(C-N) hyperconjugative interaction (cis-DDA-Li2) has a lithium ion affinity 1.7 kcal/mol lower than the nitrogen not involved in n(N) → σ*(C-N) hyperconjugative interaction (cis-DDA-Li1). In general, the computed lithium ion affinities were found to be conformationally dependent. The NBO results showed that the lithium ion affinities are also governed by the interplay of n(N) → σ*(C-N) hyperconjugative interactions and the steric strain caused upon lithiation. Further, the ring size also influences the lithium ion affinities in the 1,3-diaza monocyclic systems. In some complexes multiple coordination of the lithium ion is possible by inversion of one of the nitrogen atoms.
authors.affiliation: Analytical Science Discipline, Central Salt & Marine Chemicals Research Institute (Council of Scientific and Industrial Research), Bhavnagar 364 002, Gujarat, India.
authors.forename: Manoj K
authors.initials: MK
authors.lastname: Kesharwani
authors.forename: Walter
authors.initials: W
authors.lastname: Thiel
authors.forename: Bishwajit
authors.initials: B
authors.lastname: Ganguly
mesh_terms: D001372:Aza Compounds / Q000737:chemistry*; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000737:chemistry*; D007477:Ions / Q000737:chemistry; D008094:Lithium / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D011789:Quantum Theory
chemical_list: D001372:Aza Compounds; D019086:Bridged Bicyclo Compounds, Heterocyclic; D007477:Ions; D008094:Lithium