Low-temperature (120 K) structure and vibrational spectrum of protonated proton sponge: the adduct of 1,8-bis(dimethylamino)naphthalene (DMAN) with 4,5- dicyanoimidazole (DCI)

Abstract

Low-temperature (120 K) studies of the structure of the DMAN Á DCI adduct indicate that in symmetrical [NHN] hydrogen bridge of 2.571 (1) Å length (2.579(2) Å at room temperature) there is a disorder of the H-atom occupying two positions at nitrogen atoms with a distance of 0.94(3) Å . The comparison with the situation at room temperature seems to show a very low barrier for the proton transfer. The low-frequency vibrations with the participation of the whole N(CH 3 ) 2 groups observed in Raman and inelastic incoherent neutron scattering (IINS) spectra of about 100 cm À1 excited at room temperature cause the fundamental level of the protonic mode to penetrate or exceed the barrier. The bending CNC vibrations of about 500 cm À1 are strongly coupled with the protonic mode leading to Evans holes in the band ascribed to the 0 → 0 À transition. This hypothesis is consistent with the literature data relating to theoretical studies on H 3 NHNH 3 , which show that the barrier for the proton transfer disappears at the hydrogen bond length of about 2.55 Å .

Behavior of Highly Diluted Electrolytes in Strong Electric Fields—Prevention of Alumina Deposition on Grading Electrodes in HVDC Transmission Modules by CO2‐induced pH‐Control

“…The tunneling properties of protons are well established and account for the enhanced proton conductivity of l þ 0 (H 3 O + ) = 349.8 S cm 2 mol À1 . In the case of the protonated proton sponge 1,8-bis-(dimethylamino)naphthalene and related model compounds, the same behavior was reported experimentally [20][21][22] and theoretically. As in water, protons are generated from aqua ligands coordinated to Al + III centers on the boundary of the Pt surface and the deposition zone.…”

Structure and IR spectroscopic behaviour of 2,7-dichloro-1,8-bis(dimethylamino)naphthalene and its protonated form

“…The position of the intense, relatively narrow band with a maximum at 494 cm À1 (centre of gravity at 530 cm À1 ) is comparable to those of other symmetrical DMANÁ H cations and particularly in the symmetrical 4,5-dicyanoimidazolate adduct. 10 The only difference is that except for the weakly marked window at 565 cm À1 we do not observe deep Evans holes characteristic of other DMANÁ H cations. The formation of Evans holes was ascribed to the coupling of protonic with CNC bending vibrations which modulate the potential for the proton motion.…”

“…between the split levels in the double minimum potential. 10 In Fig. 4, the low-frequency part of the IR spectrum of DMANCl 2 Á HBr is shown.…”

Intramolecular pnicogen interactions in phosphorus and arsenic analogues of proton sponges

“…6 In 1968, this author reported the remarkable basicity of 1,8-bis(dimethylamino)naphthalene (DMAN), trademarked by Aldrich as Proton Sponge. super basicity, 7-11 vibrational spectrum, 12 including theoretical 13 NMR spectroscopy (chemical shifts and spin-spin coupling constants), [14][15][16][17][18] and experimental X-ray diffraction studies. super basicity, 7-11 vibrational spectrum, 12 including theoretical 13 NMR spectroscopy (chemical shifts and spin-spin coupling constants), [14][15][16][17][18] and experimental X-ray diffraction studies.…”