Near ultraviolet photodissociation spectroscopy of Mn+(H2O) and Mn+(D2O)

Abstract

excited states with T 0 = 30 210 and 32 274 cm −1 , respectively. Each electronic transition has partially resolved rotational and extensive vibrational structure with an extended progression in the metal−ligand stretch at a frequency of ∼450 cm −1 . There are also progressions in the in-plane bend in the 7 B 2 state, due to vibronic coupling, and the out-of-plane bend in the 7 B 1 state, where the calculation illustrates that this state is slightly non-planar. Electronic structure computations at the CCSD(T)/aug-cc-pVTZ and TD-DFT B3LYP/6-311++G(3df,3pd) level are also used to characterize the ground and excited states, respectively. These calculations predict a ground state Mn-O bond length of 2.18 Å. Analysis of the experimentally observed vibrational intensities reveals that this bond length decreases by 0.15 ± 0.015 Å and 0.14 ± 0.01 Å in the excited states. The behavior is accounted for by the less repulsive p x and p y orbitals causing the Mn + to interact more strongly with water in the excited states than the ground state. The result is a decrease in the Mn-O bond length, along with an increase in the H-O-H angle. The spectra have well resolved K rotational structure. Fitting this structure gives spin-rotation constants ε aa = −3 ± 1 cm −1 for the ground state and ε aa = 0.5 ± 0.5 cm −1 and aa = −4.2 ± 0.7 cm −1 for the first and second excited states, respectively, and A = 12.8 ± 0.7 cm −1 for the first excited state. Vibrationally mediated photodissociation studies determine the O-H antisymmetric stretching frequency in the ground electronic state to be 3658 cm −1 .

Infrared spectroscopy of the Ti(H2O)Ar+ ion–molecule complex: Electronic state switching induced by argon

“…Instead, it has symmetric multiplet structure in the higher frequency region reminiscent of the K-type structure, but each line appears to be doubled. Such additional splittings have also been seen previously for transition metal-water complexes which exhibit an unquenched spin-orbit interaction [43][44][45]. We investigate this further below.…”

“…The resolution of the laser in these experiments is about 1 cm -1 , and the rotational constants of these complexes are much smaller than this, giving rise to vibrational bands with unresolved rotational structure. In other cases when there is no argon present, or when it is present and binds on the C 2 symmetry axis leaving only the light hydrogen atoms off this axis, partially resolved K-type sub-band rotational structure can be resolved for the antisymmetric stretch band [28][29][30]34,36,37,[43][44][45]. At the low temperature expected for ions produced in this experiment, this sub-band structure usually has three prominent features; the two outer bands are spaced by about 50 cm -1 and these are more intense than the central feature because of their 3:1 nuclear spin statistical weighting factors.…”

“…Infrared photodissociation spectra have been reported previously for several cation-water complexes, including single-water and multiply solvated species in both singly-and doublycharged states [28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47]. Small complexes with water in the first solvation shell are generally studied with the method of argon or neon atom "tagging," while larger complexes can be studied via the elimination of water.…”

“…Both bands have higher computed intensities in metal complexes than for isolated water, and the symmetric stretch gains intensity relative to the antisymmetric stretch because of the more effective charge oscillation along the molecular axis. In certain M + (H 2 O) complexes, when a single rare gas atom can be used to detect photodissociation, and this atom binds on the C 2 axis of the complex, partially resolved rotational structure can be measured [28,30,34,36,37,[43][44][45]. This is possible because the three heavy atoms (metal, oxygen, rare gas) have their mass on the C 2 axis and only the light hydrogen atoms rotate around this axis.…”

Spectroscopy and photochemistry of copper nitrate clusters

“…Ultraviolet/visible/near-infrared (UV/vis/NIR) photodissociation spectroscopy is a very powerful tool to characterize the complex electronic structure of transition metal complexes and clusters in the gas phase. [44][45][46][47][48][49][50][51][52][53][54] We recently investigated photochemical hydrogen evolution from hydrated magnesium, 55,56 the effect of salt environments on the reactions and photolysis of organic substances, [57][58][59] as well as the evolution of the hydration environment of a single electron 60 or a carbon dioxide radical anion 61 using action spectroscopy.…”