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

Abstract

X-ray diffraction and IR spectroscopic studies on the proton sponge 2,7-dichloro-1,8-bis(dimethylamino)naphthalene and its adduct with HBr were performed. It was shown that the presence of the chlorine atoms in positions 2 and 7 leads to some change of conformation with respect to the free molecule. The main factor determining the conformation remains the repulsion of the nitrogen lone electron pairs. However, the repulsion between the methyl groups and chlorine atoms causes the dimethylamino groups to be slightly less twisted compared with unsubstituted dimethylaminonaphthalene. The protonation leads to the formation of a symmetrical cation (symmetry plane passing through the C9-C10 axis) with the N Á Á ÁN distance equal to 2.561(3) Å . This corresponds to the situation where the barrier to the proton transfer should be very low. As in other short [NHN] bridges, one observes the IR absorption band at about 500 cm À1 , assigned to the transition between the split O → O À vibrational levels. A very high frequency isotopic ratio (n H /n D = 1.8) is observed for this transition. a U(eq) is defined as one third of the trace of the orthogonalized U ij tensor.

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.…”

Symmetrization of Cationic Hydrogen Bridges of Protonated Sponges Induced by Solvent and Counteranion Interactions as Revealed by NMR Spectroscopy

“…On the other hand, the sum j JA C H T U N G T R E N N U N G (N,H) + JA C H T U N G T R E N N U N G (H,N) j is not reduced in the 2mono-substituted ions 11 H + and 12 H + , in which H is located preferentially on N8 (Table 1), that is, the 2-substituents are located near the lone pair and steric repulsion including angle mismatch should be operative. Therefore, although for a given compound such as 10 H + , temperature, solvent, and counteranion dependences of the three spectroscopic probes- Finally, we note that 2,7-symmetrically substituted proton sponges, in particular 8 H + [40] and 9 H + , [41] are known to exhibit unusual hydrogen-bond geometries and vibrations. However, it is difficult at present to establish a connection with the NMR spectroscopic parameters found in this study.…”

“…[39] Prior to this, protonated sponges of the DMANH + type were studied mainly by a combination of various experimental and theoretical methods and had focused on the question of whether or not the proton moves in a single or double well. [40][41][42][43] In solution, such information was obtained by studying the effects of isotopic substitution on NMR spectroscopic chemical shifts. [11,44] Other NMR spectroscopic studies of protonated 1,8-bis(dimethylamino)naphthalenes focused on the determination of the equilibrium constants of tautomerism by analyzing the temperature dependence of the coupling constants JA C H T U N G T R E N N U N G (N,H) and JA C H T U N G T R E N N U N G (H,N).…”

Molecular structure of 5,6-bis(dimethylamino)acenaphthene, 5,6-bis(dimethylamino)acenaphthylene, and their monohydrobromides: a comparison with some naphthalene proton sponges

“…Besides, 2,7-dichloro derivative 5 represents the naphthalene proton sponge with a relatively rigid structure, in which the dimethylamino groups are brought together and fixed in a face-to-face conformation. 7 On the other hand, voluminous peri-substituents in tetramine 4 should strengthen an acoplanarity of the whole molecule. 6 The most important structural change in molecules 1 and 2 and in their cations in comparison with proton sponges 3-5 (Table 2) is a strong increase in N ؒ ؒ ؒ N distance which is especially marked for acenaphthylene 2 (2.955 Å).…”

“…Data for proton sponge 3 were accepted from ref [4],. 3ؒHBr from[5], 4 and 4ؒ2HBr from[6], 5 and 5ؒHBr from[7], and 1 and 2 (pK a and δ NH values) from[1]. Bolded parameters in the Table are in a qualitative correlation.…”