Electronic spectroscopy of malondialdehyde

Comparison of methods for calculating the properties of intramolecular hydrogen bonds. Excited state proton transfer

“…The measurements of the excited states of malonaldehyde consist largely of tunneling splitting data. 69 A smaller splitting in the 1 n* state, as compared to S o , [70][71][72] confirms the computational finding of a higher barrier in this excited state, ͑although later work questioned this interpretation͒. 73 Other experimental measurements are consistent with our computational finding that the 1 n* state of malonaldehyde is lower than 1 n*.…”

“…73 Other experimental measurements are consistent with our computational finding that the 1 n* state of malonaldehyde is lower than 1 n*. 70,72 While there is no information on the asymmetric glyoxalmonohydrazine molecule itself, there are a number of studies of larger systems that contain the OH¯N intramolecular interaction within the context of one or more aromatic rings. These confirm the computational finding that the proton transfer barrier is much reduced in the 1 * state as compared to S o ͑Refs.…”

Proton transfer dynamics in the first excited singlet state of malonaldehyde

“…Since the weak à 1 B 1 -X 1 A 1 system is electric dipole allowed only under type-c selection rules, the presence of a-polarized and b-polarized bands would implicate a Herzberg-Teller vibronic coupling mechanism 28 which, as well documented for the analogous à 1 A 2 -X 1 A 1 (*←n) spectrum of formaldehyde, 29 causes mixing of electronic parentage among neighboring states. For malonaldehyde, intense *← absorption features assigned to the B 1 B 2 -X 1 A 1 and C 1 A 1 -X 1 A 1 resonances have been reported 11 in the vicinity of 4.5 and 5.9 eV. Admixture of B 1 B 2 (*) and C 1 A 1 (*) character into the à 1 B 1 (*n) manifold will be mediated by vibrations of a 2 and b 1 symmetry, thereby resulting in the appearance of a-polarized and b-polarized features.…”

“…In the near-ultraviolet region of the spectrum, Seliskar and Hoffmann 11,12 have identified a weak, highly structured absorption system which stems from a *←n electron promotion. These authors proposed the pertinent excited state to be of 1 B 1 symmetry, with the corresponding à 1 B 1 -X 1 A 1 transition moment directed orthogonal to the molecular plane ͓i.e., a type-c transition as per Eq.…”

“…While traditional ͑linear͒ absorption methods provide a viable means for accomplishing such measurements, [11][12][13] the overall utility of this approach is limited by the small à -X oscillator strength and the requirement for high spectral resolution. As demonstrated by studies conducted in our laboratory [15][16][17] and at other facilities, 18-20 nonlinear optical techniques built upon the concepts of four-wave mixing 21,22 can provide an absorption-based probe of molecular structure and dynamics which combines trace sensitivity and laserlimited resolution with general species applicability.…”