TY - JOUR
T1 - Exploring Ultrashort Hydrogen-Hydrogen Nonbonded Contacts in Constrained Molecular Cavities
AU - Mandal, Nilangshu
AU - Pratik, Saied Md
AU - Datta, Ayan
PY - 2017/2/2
Y1 - 2017/2/2
N2 - Confined molecular chambers such as macrocycle bridged E1-H···H-E2 (E1(E2) = Si(Si), 1) exhibit rare ultrashort H···H nonbonded contacts (d(H···H) = 1.56 Å). In this article, on the basis of density functional theory and ab initio molecular dynamics simulations, we propose new molecular motifs where d(H···H) can be reduced to 1.44 Å (E1(E2) = Si(Ge), 3). Further tuning the structure of the macrocycle by replacing the bulky phenyl groups by ethylenic spacers and substitution of the H-atoms by -CN groups makes the cavity more compact and furnishes even shorter d(H···H) = 1.38 Å (E1(E2) = Ge(Ge), 8). These unusually close H···H nonbonded contacts originate from the strong attractive noncovalent interactions between them, which are evident from various computational indicators, namely, NCI, Wiberg bond index, relaxed force constant, quantum theory of atoms in molecules, and natural orbitals for chemical valence combined with the extended transition state method analyses. Substantial stabilization of the in,in-configuration (exhibiting short H···H contacts) compared with the out,out-configuration (by ∼5.7 kcal/mol) and statistically insignificant fluctuations in 〈d(H···H)〉 and 〈θav〉(θ(E1(E2)-H···H = 152°) at room temperature confirm that the ultrashort H···H distances in these molecules are thermodynamically stable and would be persistent under ambient experimental conditions.
AB - Confined molecular chambers such as macrocycle bridged E1-H···H-E2 (E1(E2) = Si(Si), 1) exhibit rare ultrashort H···H nonbonded contacts (d(H···H) = 1.56 Å). In this article, on the basis of density functional theory and ab initio molecular dynamics simulations, we propose new molecular motifs where d(H···H) can be reduced to 1.44 Å (E1(E2) = Si(Ge), 3). Further tuning the structure of the macrocycle by replacing the bulky phenyl groups by ethylenic spacers and substitution of the H-atoms by -CN groups makes the cavity more compact and furnishes even shorter d(H···H) = 1.38 Å (E1(E2) = Ge(Ge), 8). These unusually close H···H nonbonded contacts originate from the strong attractive noncovalent interactions between them, which are evident from various computational indicators, namely, NCI, Wiberg bond index, relaxed force constant, quantum theory of atoms in molecules, and natural orbitals for chemical valence combined with the extended transition state method analyses. Substantial stabilization of the in,in-configuration (exhibiting short H···H contacts) compared with the out,out-configuration (by ∼5.7 kcal/mol) and statistically insignificant fluctuations in 〈d(H···H)〉 and 〈θav〉(θ(E1(E2)-H···H = 152°) at room temperature confirm that the ultrashort H···H distances in these molecules are thermodynamically stable and would be persistent under ambient experimental conditions.
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U2 - 10.1021/acs.jpcb.6b12391
DO - 10.1021/acs.jpcb.6b12391
M3 - Article
C2 - 28055206
AN - SCOPUS:85020444323
SN - 1520-6106
VL - 121
SP - 825
EP - 834
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
IS - 4
ER -