DFT investigation on the intramolecular and intermolecular proton transfer processes in 2-aminobenzothiazole (ABT) in the gas phase and in different solvents

Quantum Chemical Microsolvation by Automated Water Placement

“…Hence, we set up the microsolvated structures with two explicit water molecules to yield T1-(H 2 O) 2 and T2-(H 2 O) 2 and optimized them ( Figure 7 E,F). The microsolvation shifts the equilibrium by decreasing the energy difference between the two isomers Δ E rel = E (T2-(H 2 O) 2 ) − E (T1-(H 2 O) 2 ) to 2.9 kcal/mol (gas phase) and 4.5 kcal/mol (implicit solvent), respectively—a finding in agreement with previously published results [ 49 ]. More strikingly, however, the predicted number of two water molecules forming a water chain and aiding the proton transfer process coincides with previous results found by trial and error [ 49 ].…”

“…The microsolvation shifts the equilibrium by decreasing the energy difference between the two isomers Δ E rel = E (T2-(H 2 O) 2 ) − E (T1-(H 2 O) 2 ) to 2.9 kcal/mol (gas phase) and 4.5 kcal/mol (implicit solvent), respectively—a finding in agreement with previously published results [ 49 ]. More strikingly, however, the predicted number of two water molecules forming a water chain and aiding the proton transfer process coincides with previous results found by trial and error [ 49 ]. Wazzan et al reported that two water molecules minimize the barrier for proton transfer from T1 to T2, whereas chains consisting of one or three water molecules result in higher barriers.…”

“…Previous studies have shown that water assists the tautomerization process and the conversion from T1 to T2. A microsolvation model was required to calculate meaningful transition state structures and reaction barriers, while the number and location of the explicitly treated water molecules was determined by trial and error [ 49 ]. Our goal was to investigate whether our microsolvation protocol is able to yield reasonable microsolvated structures.…”

“…The user can choose the number of explicit solvent molecules for subsequent quantum chemical studies based on their position and interaction strength. We chose five different small molecules, which differ in size and polarity, to test our methodology: urea and benzoic acid due to their biological relevance; (+)- syn -benzotriborneol because of its ability to act as a water receptor [ 48 ]; helicene because of its apolar nature; and 2-aminobenzothiazole, which can undergo water-assisted tautomerization [ 49 ]. All of these molecules have previously been investigated either experimentally by rotational spectroscopy as well as X-ray and neutron diffraction analysis or theoretically by quantum chemical or molecular dynamics studies [ 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 ].…”

Electron‐donor substituents on the dppz‐based ligands to control luminescence from dark to bright emissive state in Ir(III) complexes

“…In the case of Ir‐1 , the slight out‐of‐plane deformation could be associated with the bulky tert‐butyl substituent, whereas in Ir‐5 the distortion is attributable to the hindrance methoxy substituents bonded at C 4 and C 5 carbon atoms due to the ortho‐substitution, considering that ortho‐substituents are more sterically hindered compare meta‐ or para‐substitutions . Probably, these distortions could be restrict the electron donation abilities of the substituents in Ir‐1 and Ir‐5 , by both inductive and resonance effects.…”