Effects of counterion and solvent on proton location and proton transfer dynamics of N-H···N hydrogen bond of monoprotonated 1,8-bis(dimethylamino)naphthalene.
The proton location and proton transfer (PT) dynamics of a hydrogen bond are under the influence of the static and dynamical properties of the solvent and counterions. In the present study, the N-H distances were determined for salts of 1,8-bis(dimethylamino)naphthalene, DMANH(+)X(-) (X(-) = BPh4(-), ClO4(-), and Cl(-)), in acetonitrile (AN) solution, and DMANH(+)Br(-) in water by observing the (15)N spin-lattice relaxation caused by the (15)N-(1)H magnetic dipolar coupling under assumption that the PT time was shorter than the NH reorientation time (∼10(-11) s). The obtained N-H distances decreased in the following order: DMANH(+)BPh4(-) > DMANH(+)ClO4(-) > DMANH(+)Br(-)/H2O > DMANH(+)Cl(-), indicating that interactions with the environment affect the PT potentials. To understand the results at the molecular level, Car-Parrinello molecular dynamics simulations were performed for DMANH(+), DMANH(+) in water, and DMANH(+)-Cl(-) ion-pair in AN. The results of simulation suggest that (1) the N-H distance decreases in the presence of a solvent and counterion; (2) the PT time is probably ∼10(-12) s, which confirms the above assumption used for the NMR relaxation data analyses; and (3) fluctuation of the interactions with the solvent or counterion has a significant role in PT. Quantum nuclear effects on the hydrogen bond were also examined.
Department of Chemistry, Faculty of Science, Ochanomizu University , Otsuka, Bunkyo-ku, Tokyo 112-8610, Japan.
Yuichi
Y
Masuda
Yukie
Y
Mori
Kazumi
K
Sakurai
D015057:1-Naphthylamine / Q000031:analogs & derivatives* / Q000737:chemistry; D006859:Hydrogen / Q000737:chemistry*; D006860:Hydrogen Bonding; D007477:Ions; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D009584:Nitrogen / Q000737:chemistry*; D011522:Protons; D012997:Solvents / Q000737:chemistry*
D007477:Ions; D011522:Protons; D012997:Solvents; C418992:1,8-bis(dimethylamino)naphthalene; D006859:Hydrogen; D015057:1-Naphthylamine; D009584:Nitrogen