Rotational spectra and gas phase structure of the maleimide – Formic acid doubly hydrogen bonded dimer

Abstract

Rotational transitions were measured for the maleimide-formic acid doubly hydrogen bonded dimer using a Flygare-Balle type pulsed-beam Fourier transform microwave spectrometer. No splittings caused by possible concerted double proton tunneling motion were observed. Experimental rotational constants (MHz), quadrupole coupling constants (MHz), and centrifugal distortion constants (kHz) were determined for the parent and three deuterium substituted isotopologues. The values for the parent are A = 2415.0297(10), B = 784.37494(38), C = 592.44190(33), D J = 0.0616(64), D JK =-0.118(35), D K =-1.38(15), 1.5χ aa = 2.083(14), and 0.25(χ bb-χ cc) = 1.1565(29). The hydrogen bond lengths were determined using a nonlinear least squares structure fitting program. Rotational constants for this complex are consistent with a planar structure, with an inertial defect of ∆ =-0.528 amu Å 2. The B3LYP calculation yielded rotational constants within 0.1% of the experimental values.

Synthesis, microwave spectra, x-ray structure, and high-level theoretical calculations for formamidinium formate

“…No tunneling splittings were observed for formic acid-formamide, 6 1,2-cyclohexanedione-formic acid 7 or cyclopropanecarboxylic acid-formic acid, 8 or the maleimide -formic acid complex. 9 Tropolone -formic acid has the C2v(m) symmetry but splittings were not observed due to the high barrier. 10 There are theoretical calculations of double proton transfers in the formamidine formic acid dimer by Kim, Lim and Kim, 11 Lim, Lee and Kim, 12 Park, Kim, Kim and Kim, 13 Radom, 14 et al, and Simperler, Mikenda, and Schwarz.…”

Formic Acid–Ammonia Heterodimer: A New Δ-Machine Learning CCSD(T)-Level Potential Energy Surface Allows Investigation of the Double Proton Transfer

“…Doubly bonded complexes with asymmetric double-well potentials and lacking the C 2v (m) symmetry are much less likely to show tunneling splittings in the spectra. Additional doubly hydrogen-bonded complexes are formic acid trifluoro acetic acid, 19 formic acid−malemide, 20 formic acid�glyoxylic acid, 21 formic acid−difluoro acetic acid, 22 formic acid�acrylic acid, 23 and formic acid�perfluorobutyric acid. 24 Double proton hopping is debated also regarding DNA nucleobase pairs, like the guanine-cytosine pair, due to its importance in genetic transcription and mutagenesis.…”

Microwave Measurements of the Tropolone-Formic Acid Doubly Hydrogen Bonded Dimer*

“…Some other doubly hydrogen bonded dimers do not exhibit the concerted proton tunneling. 26,27 We recently reported the microwave spectrum of cyclopropanecarboxylic acid-formic acid (CPCA-FA) dimer 28 and no tunneling was observed for this doubly hydrogen bonded dimer. The doubly hydrogen bonded tropolone-formic acid dimer introduces a new interesting question about whether or not the tunneling splitting can be observed in this larger more symmetric complex.…”