Proton Donor Molecules Research Articles

Development of cat-GRRM/MC/MD method for the simulation of cross-linked network structure formation with molecular autocatalysis

Epoxy resins, which are common matrices in carbon fibre-reinforced plastics, are derived from the curing of epoxy amines. Molecular dynamics (MD) simulations are commonly used to model the physical properties of such network polymers, but they do not account for chemical reactions. Quantum chemical (QC) calculations can elucidate reaction mechanisms and energies but are not suitable for models with thousands of atoms. To address these limitations, in this study, we developed a new method, cat-GRRM/MC/MD, that combines QC calculations in the Global Reaction Route Mapping (GRRM) program with reaction simulations involved in MD simulation methods. This approach allows the simulation of reaction pathways in which proton donor molecules such as alcohols and amines act as molecular catalysts (autocatalysis), and the reaction kinetics are realised in a Monte Carlo (MC) manner. Our results show that autocatalysis significantly reduces the activation energy of the epoxy resin reaction, bringing the calculated data closer to the experimental results. When these quantum chemical calculations were incorporated into MD simulations, it was found that the activation energy influenced the crosslinking results. Models including catalysis led to network polymers with larger carbon skeletons, and physical properties such as the Young's modulus and glass transition temperature become closer to experimental results. This study not only deepens our understanding of the mechanism of the self-catalytic reaction of epoxy resins but also provides a new tool for accurately simulating the performance of epoxy resins, thus enabling more precise control of their properties.

Unveiling the Noncovalent Interaction of Thiazol-2-ylidene and Its Derivatives as N-heterocyclic Carbene with Different Proton Donor Molecules.

The importance of noncovalent interaction has gained attention in various domains covering drug and novel catalyst design. The present study mainly characterizes the role of hydrogen bond (H-bond) and other intermolecular interactions in different (1 : 1) complex analogues formed between the N-aryl-thiazol-2-ylidene (YR) and five proton donor (HX) molecules. The analysis of the singlet-triplet energy gap ( ) confirmed the stability of the singlet state for this class of N-aryl-thiazol-2-ylidenes than the triplet state. The interaction energy values of the YR-HX complexes follow the order: YR-NH3 <YR-HCN<YR-H2 O<YR-MeOH<YR-HF. In addition, substituting the H-atom of the N-H bond with bulky groups (-R) leads to an increase in the interaction energy of the YR-HX complexes. Hence, it was found that the replacement of N-atom in N-heterocyclic carbene (NHC) by S-atom forming N-aryl-thiazol-2-ylidene results in comparable intermolecular interactions with proton donor molecules similar to imidazole-2-ylidene (NHC). The current study enlightened the role of noncovalent interactions in carbene complexes with proton donor molecules. We hope that our work on carbene chemistry will pave the way for its application in the designing and synthesis of efficient catalysts.

On the Coexistence of the Carbene⋯H-D Hydrogen Bond and Other Accompanying Interactions in Forty Dimers of N-Heterocyclic-Carbenes (I, IMe2, IiPr2, ItBu2, IMes2, IDipp2, IAd2; I = imidazol-2-ylidene) and Some Fundamental Proton Donors (HF, HCN, H2O, MeOH, NH3).

The subject of research is forty dimers formed by imidazol-2-ylidene (I) or its derivative (IR) obtained by replacing the hydrogen atoms in both N-H bonds with larger important and popular substituents of increasing complexity (methyl = Me, iso-propyl = Pr, tert-butyl = Bu, phenyl = Ph, mesityl = Mes, 2,6-diisopropylphenyl = Dipp, 1-adamantyl = Ad) and fundamental proton donor (HD) molecules (HF, HCN, HO, MeOH, NH). While the main goal is to characterize the generally dominant C⋯H-D hydrogen bond engaging a carbene carbon atom, an equally important issue is the often omitted analysis of the role of accompanying secondary interactions. Despite the often completely different binding possibilities of the considered carbenes, and especially HD molecules, several general trends are found. Namely, for a given carbene, the dissociation energy values of the IRHD dimers increase in the following order: NH< HO < HCN ≤ MeOH ≪ HF. Importantly, it is found that, for a given HD molecule, IDipp forms the strongest dimers. This is attributed to the multiplicity of various interactions accompanying the dominant C⋯H-D hydrogen bond. It is shown that substitution of hydrogen atoms in both N-H bonds of the imidazol-2-ylidene molecule by the investigated groups leads to stronger dimers with HF, HCN, HO or MeOH. The presented results should contribute to increasing the knowledge about the carbene chemistry and the role of intermolecular interactions, including secondary ones.

Detailed analysis of induced smectic phases and paramorphic effect of double hydrogen bonded ferroelectric liquid crystals

A novel double hydrogen bonded ferroelectric liquid crystal (HBFLC) complex was isolated from (R)-(+)-Methylsuccinic acid (RMSA) and 4-Nonyloxybenzoic acid (9OBA). The presence of hydrogen bond between proton donor (RMSA) and proton acceptor (9OBA) molecules were characterized by FT-IR spectroscopy. Mesomorphic behavior and its phase transition temperature of the HBFLC complex (1:1 and 1:2 ratio) were studied by differential scanning calorimeter (DSC), polarized optical microscope (POM) and identified smectic A*, smectic C* and smectic G* phases by quenching of nematic. MSA + 9OBA HBFLC complex has strong dipole moment which is vertical to the lengthy molecular axis provide a pathway to the insight of smectic mesophases. Sm C* phase revealed paramorphic effect due to refractive index changes in the H-bond layers and leads violet to red color textures. Stabilization of the smectic phase by dipole-dipole interaction in the HBFLC complex was reported using density functional theory (DFT) analysis. Stability of the phase increase while increasing the mesogenic ratio in the present HBFLC complex was also discussed. The structure of the MSA + 9OBA HBFLC complex was optimized by B3LYP theory with the basis set of 6311-G (d, p). In natural bond orbital analysis, it was found that the high stabilization energy specified the intermolecular interaction among the molecules.

Kinetic Evidence for the Necessity of Two Proton Donor Molecules for Successful Excited State Proton Transfer by a Photobase.

Photobases are molecules that convert light to proton transfer drive and therefore have potential applications in many areas of chemistry. Previously, we studied the photobasicity of quinolines and explored their applications. While it is possible to tether a photobase near a target proton donor, for the sake of versatility it is desirable to explore their capability to deprotonate molecules dispersed in a solution. Previous evidence suggested that in this scenario at least two proton donors were necessary for successful excited state proton transfer: one to donate a proton and the second to stabilize the photogenerated donor anion. Here we report kinetic evidence from transient absorption (TA) and time-correlated single photon counting (TCSPC) in support of this hypothesis. We used 5-methoxyquinoline as the photobase and 2,2,2-trifluoroethanol (TFE), a low pKa alcohol, as the proton donor. A constant concentration of the photobase was used for a range of proton-donor dilutions spanning several orders of magnitude in an aprotic background solvent. Absorption spectra confirm that over most of the studied range the majority of the photobase population is hydrogen bonded to at least one donor. Short-pulse TA was used to measure the faster (2-500 ps) dynamics, while TSCPC was used to measure the slower (>500 ps) dynamics. The measured proton transfer time constants varied as a function of donor concentration over a wide range. A log-log plot of the proton transfer rate constant as a function of proton-donor concentration shows two regimes: nondiffusive at high donor concentrations where multiple proton donors are near the photobase and diffusive at low donor concentrations where proton donors are more dilute. The nondiffusive regime has a slope of approximately one, suggesting that the proton transfer process is dependent on one donor molecule in addition to the donor molecule already hydrogen bonded with the photobase. The diffusive regime reasonably follows diffusion kinetics. We propose a model for how the second proton-donor molecule may interact with the photogenerated alkoxide to stabilize it. This work highlights the importance of inducing irreversible changes, in this case solvation of the alkoxide, after proton transfer. Understanding of such details is likely to be important in applications of photobases.

Effect of solvent nature on spectral properties of blue-emitting meso-propargylamino-BODIPY

The spectral and luminescent properties of meso-propargylamino-boron (III) dipyrromethenate (BODIPY 1) were studied in a wide range of organic solvents of different polarities, electron- and proton-donating abilities. Effect of organic solvents on the properties of the BODIPY 1 spectral characteristics was analyzed in details. It was shown that the fluorescence of BODIPY 1 is characterized by a high sensitivity to the nature of the solvent. It was found that the complex, which emits in the blue-green region (433–486 nm), has a high quantum yield of fluorescence (~100%) in non-polar media (cyclohexane, benzene, toluene), while in proton- and especially electron donor media, sharp fluorescence quenching (2.2–31.2 times) of the dye is observed. For a better understanding of the spectral analysis results, a quantum-chemical analysis of the molecular structure, electronic structure, and spectral characteristics of BODIPY 1 was carried out. For the first time, it was shown that BODIPY 1 fluorescence quenching in proton and electron donor media is caused by the formation of a supramolecular dye complex due to specific interactions of solvent molecules with atoms of the meso-propargylamine group. Due to practically useful spectral properties, including the sensitivity of the fluorescence to the nature of the media, BODIPY 1 is recommended as a new effective fluorescent sensor of specific electron and proton donor molecules.

Microhydration and the Enhanced Acidity of Free Radicals.

Recent theoretical research employing a continuum solvent model predicted that radical centers would enhance the acidity (RED-shift) of certain proton-donor molecules. Microhydration studies employing a DFT method are reported here with the aim of establishing the effect of the solvent micro-structure on the acidity of radicals with and without RED-shifts. Microhydration cluster structures were obtained for carboxyl, carboxy-ethynyl, carboxy-methyl, and hydroperoxyl radicals. The numbers of water molecules needed to induce spontaneous ionization were determined. The hydration clusters formed primarily round the CO2 units of the carboxylate-containing radicals. Only 4 or 5 water molecules were needed to induce ionization of carboxyl and carboxy-ethynyl radicals, thus corroborating their large RED-shifts.

Gold(I) Hydrides as Proton Acceptors in Dihydrogen Bond Formation.

Wavefunction and DFT calculations indicate that anionic dihydride complexes of AuI form strong to moderate directed Au-H⋅⋅⋅H bonds with one or two HF, H2 O and NH3 prototype proton donor molecules. The largely electrostatic interaction is influenced by relativistic effects which, however, do not increase the binding energy. Very weak Au⋅⋅⋅H associations-exhibiting a corresponding bond path-occur between neutral AuH and HF units, although ultimately F becomes the preferred donor atom in the most stable structure. Increasing the hydridicity of AuH by attachment of an electron donating NHC ligand effects Au-H⋅⋅⋅H bonding of moderate strength only with HF, whereas competing Au⋅⋅⋅H interactions dominate for H2 O and NH3 . Rare η2 coordinated and HX (X=F or OH) associated H2 complexes are produced during interaction with a single ion of stronger acidity, H2 F+ or H3 O+ . Theoretically, reaction of excess [AuH2 ]- as proton acceptor with H3 O+ or NH4+ in 3:1 or 4:1 ionic ratios, respectively, affords H⋅⋅⋅H bonded analogues of Eigen-type adducts. Outstanding analytical relationships between selected bonding parameters support the integrity of the results.

Effects of zero point vibration on the reaction dynamics of water dimer cations following ionization.

Reactions of water dimer cation (H2O)2+ following ionization have been investigated by means of a direct ab initio molecular dynamics method. In particular, the effects of zero point vibration and zero point energy (ZPE) on the reaction mechanism were considered in this work. Trajectories were run on two electronic potential energy surfaces (PESs) of (H2O)2+: ground state (2 A″-like state) and the first excited state (2 A'-like state). All trajectories on the ground-state PES lead to the proton-transferred product: H2 O+ (Wd)-H2 O(Wa) → OH(Wd)-H3 O+ (Wa), where Wd and Wa refer to the proton donor and acceptor water molecules, respectively. Time of proton transfer (PT) varied widely from 15 to 40 fs (average time of PT = 30.9 fs). The trajectories on the excited-state PES gave two products: an intermediate complex with a face-to-face structure (H2 O-OH2 )+ and a PT product. However, the proton was transferred to the opposite direction, and the reverse PT was found on the excited-state PES: H2 O(Wd)-H2 O+ (Wa) → H3 O+ (Wd)-OH(Wa). This difference occurred because the ionizing water molecule in the dimer switched between the ground and excited states. The reaction mechanism of (H2O)2+ and the effects of ZPE are discussed on the basis of the results. © 2017 Wiley Periodicals, Inc.

N-Hydroxyurea dimers: A matrix isolation and theoretical study

The dimerization of N-hydroxyurea (NH2CONHOH) has been investigated by FTIR matrix isolation spectroscopy and DFT(B3LYP)/6-311++G(2d,2p) calculations. The analysis of NH2CONHOH/Ar matrix spectra and comparison with theoretical ones reveal the formation of two types of dimers with a strong OH⋯O hydrogen bond. There is an additional weak interaction between the oxygen atom of the OH group of the proton donor molecule and the NH or NH2 group of the proton acceptor in both dimers, respectively. The identified structures correspond to local minima on the PES. The formation of the less stable structures not the most stable ones indicates that the creation of N-hydroxyurea dimers is related to the dipole-dipole interaction at the initial stage of the dimerization process, which favours generation of polar dimers.

Effect of Substituents on Hydrogen Bond Strength in Hydrogen-Bonded &lt;em&gt;N&lt;/em&gt;-methylacetamide and Uracil Complexes

Theoretical calculations on a series of N-H…O=C hydrogen-bonded complexes containing 1-methyluracil and N-methylacetamide were carried out using B3LYP and MP2 methods. Substituent effects in the hydrogen bond acceptor molecule (1-methyluracil) on the hydrogen bond strength and hydrogen bond cooperativity were explored. The calculation results show that electron donating groups shorten the H…O distance and strengthen the N-H…O=C hydrogen bond, whereas electron withdrawing groups lengthen the H…O distance and weaken the N-H…O=C hydrogen bond. Natural bond orbital (NBO) analysis further indicates that electron donating groups result in a larger positive charge on the H atom and a larger negative charge on the O atom in the N-H…O=C bond, and result in increased charge transfer between the proton donor and acceptor molecules. Electron withdrawing groups show the opposite results. NBO analysis also indicates that electron donating groups result in larger second-order interaction energies between the oxygen lone pair and the N - H antibonding orbital when compared to the 1-methyluracil-containing complex (R=H), while electron withdrawing groups result in smaller second-order interaction energies.

Excited-State Intermolecular Proton Transfer of Firefly Luciferin V. Direct Proton Transfer to Fluoride and Other Mild Bases

We studied the direct proton transfer (PT) from electronically excited D-luciferin to several mild bases. The fluorescence up-conversion technique is used to measure the rise and decay of the fluorescence signals of the protonated and deprotonated species of D-luciferin. From a base concentration of 0.25 M or higher the proton transfer rates to the fluoride, dihdyrogen phosphate or acetate bases are fast and comparable. The fluorescence signals are nonexponential and complex. We suggest that the fastest decay component arises from a direct proton transfer process from the hydroxyl group of D-luciferin to the mild base. The proton donor and acceptor molecules form an ion pair prior to photoexcitation. Upon photoexcitation solvent rearrangement occurs on a 1 ps time-scale. The PT reaction time constant is ∼2 ps for all three bases. A second decay component of about 10 ps is attributed to the proton transfer in a contact pair bridged by one water molecule. The longest decay component is due to both the excited-state proton transfer (ESPT) to the solvent and the diffusion-assisted PT process between a photoacid and a base pair positioned remotely from each other prior to photoexcitation.

Identification of two quanta simultaneous vibrational transitions in the dimer water trapped in inert matrices

Two quanta transitions involving the vibrational excitation of both proton donor (PD) and proton acceptor (PA) molecules of the water dimer trapped in inert matrices, a particular case of similtaneous transitions, have been identified. They are characterized by weaker intensity and smaller anharmonicity than the usual combinations of PD or PA. In some cases their intensity is strongly enhanced by quasi perfect resonances with PD combinations, as proved by decoupling effects in 18O/ 16O isotopic mixtures.

A computational study of ultrafast acid dissociation and acid-base neutralization reactions. I. The model

Ultrafast, time-resolved investigations of acid-base neutralization reactions have recently been performed using systems containing the photoacid 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS) and various Bronsted bases. Two conflicting neutralization mechanisms have been formulated by Mohammed et al. [Science 310, 83 (2005)] and Siwick et al. [J. Am. Chem. Soc. 129, 13412 (2007)] for the same acid-base system. Herein an ab initio molecular dynamics based computational model is formulated, which is able to investigate the validity of the proposed mechanisms in the general context of ground-state acid-base neutralization reactions. Our approach consists of using 2,4,6-tricyanophenol (exp. pKa congruent with 1) as a model for excited-state HPTS( *) (pKa congruent with 1.4) and carboxylate ions for the accepting base. We employ our recently proposed dipole-field/quantum mechanics (QM) treatment [P. Maurer and R. Iftimie, J. Chem. Phys. 132, 074112 (2010)] of the proton donor and acceptor molecules. This approach allows one to tune the free energy of neutralization to any desired value as well as model initial nonequilibrium hydration effects caused by a sudden increase in acidity, making it possible to achieve a more realistic comparison with experimental data than could be obtained via a full-QM treatment of the entire system. It is demonstrated that the dipole-field/QM model reproduces correctly key properties of the 2,4,6-tricyanophenol acid molecule including gas-phase proton dissociation energies and dipole moments, and condensed-phase hydration structure and pKa values.

On the Assessment of Some New Meta-Hybrid and Generalized Gradient Approximation Functionals for Calculations of Anharmonic Vibrational Frequency Shifts in Hydrogen-Bonded Dimers

The performance of some recently proposed DFT functionals by Truhlar's group (mPW1B95, mPWLYP1W, PBELYP1W, and PBE1W [Dahlke, E. E.; Truhlar, D. G. J. Phys. Chem. B 2005, 109, 317. Zhao, Y.; Truhlar, D. G. J. Phys. Chem. A 2004, 108, 6908.]) was tested primarily with respect to computation of anharmonic vibrational frequency shifts upon hydrogen bond formation in small molecular/ionic dimers. Five hydrogen-bonded systems with varying hydrogen bond strengths were considered: methanol-fluorobenzene, phenol-carbon monoxide in ground neutral (S(0)) and cationic (D(0)) electronic states, phenol-acetylene, and phenol-benzene(+). Anharmonic OH stretching frequency shifts were calculated from the computed vibrational potentials for free and hydrogen-bonded proton-donor molecules. To test the basis set convergence properties, all calculations were performed with 6-31++G(d,p) and 6-311++G(2df,2pd) basis sets. The mPW1B95 functional was found to perform remarkably better in comparison to more standard functionals (such as B3LYP, mPW1PW91, PBE1PBE) in the case of neutral dimers. In the case of cationic dimers, however, this is not always the case. With respect to prediction of anharmonic OH stretching frequency shifts upon ionization of free phenol, all DFT levels of theory outperform MP2. Some other aspects of the functional performances with respect to computation of interaction and dissociation energies were considered as well.

New synthetic route to modafinil drug including desulfobenzhydrylation of sodium carbamoylmethyl thiosulfate: experimental and quantum chemical studies

A new synthetic route to 2-benzhydrylsulfinylacetamide (1), a nootropic drug modafinil, is described. The synthesis includes the alkylation of sodium thiosulfate with chloroacetamide to sodium carbamoylmethyl thiosulfate, the desulfobenzhydrylation of the latter by benzhydrol in formic acid to form benzhydrylthioacetamide (3a), and the further oxidation of this thioamide with hydrogen peroxide. According to B3LYP/6-31G** DFT calculations, the key step of the synthesis, namely, desulfobenzhydrylation of salt 6a, occurs only insignificantly due to the energetically unfavorable direct attack of this salt by benzhydryl formate; the reaction mainly involves the attack by the benzhydrilium carbocation Ph2CH+. The oxidation of sulfide 3a to sulfinylacetamide 1 is efficiently catalyzed by side proton-donor molecules (constituents of the transition states of the reaction). The oxidant can be the anionic form of the reactant (HO2- ion), which reacts with sulfide 3avia the unusual noncatalytic mechanism. At the step of transition state formation, this mechanism resembles the SN2 substitution.

Density functional theory study of the free and tetraprotonated spheroidal macrotricyclic ligands and the complexes with halide anions: F−, Cl−, Br−

Theoretical studies of the macrotricyclic tetramine hexaether (SC), its tetraprotonated form SC-4H(+), and the corresponding complexes X(-) subsetSC-4H(+) (This expression represents the structural properties of the halide inclusion complex formed though the free ligand SC-4H(+) and the halide anion X(-): the spherical halide anion X(-) is held by a tetrahedral array of (+)N--H...X(-) hydrogen bonds inside the intramolecular cavity of the tetraprotonated form SC-4H(+)) of SC-4H(+) with the halide anions: F(-), Cl(-), and Br(-) have been performed using density functional theory (DFT) with B3LYP/6-31G method implemented in the Gaussian 03 program package. The optimized geometric structures obtained from DFT calculations are used to perform Natural Bond Orbital (NBO) analysis. The three main types of hydrogen bonds (+)N--H...F(-), (+)N--H...Cl(-), and (+)N--H...Br(-) are investigated. The results indicate that hydrogen bonding interactions are dominant and the halide anions: F(-), Cl(-), and Br(-) offer lone pair electrons to the contacting sigma* (N--H) antibond orbital of SC-4H(+). For all the structures, the most pronounced changes in geometric parameters upon interaction are observed in the proton-donor molecule. The intermolecular interaction energies are predicted by using B3LYP/6-31G methods with basis set superposition error (BSSE) and zero-point energy (ZPE) correction.

Calculations of vibrational frequencies, Raman activities and degrees of depolarization for complexes involving water, methanol and ethanol

Raman activities and degrees of depolarization are reported for 14 complexes involving methanol, ethanol and water using the MP2/aug-cc-pVDZ model. For ethanol both trans and gauche isomers are considered. The red-shifts of the OH stretching and the blue shifts of the bending τ CO–OH mode were analyzed for the proton-donor molecules upon hydrogen bond. The shift of the ν CO stretching mode of the alcohol molecules are also analyzed and found to be specific giving characterization of the amphoteric relation, being positive for the proton-acceptor and negative for the proton-donor molecule.

A density functional theory study of the structure and tautomerism of hydrophosphoryl compounds

The geometry, electron density distribution, dipole moments, energy and nodal properties of frontier orbitals, and relative stability of tautomeric forms were studied using density functional theory (PBE, TZ2p basis set) for a representative series of the RR’P(H)O (IIIa) ⇆ RR’POH (IIIb) (R, R’ = H, CH3, CF3, C6H5, C6F5, N(CH3), OCH3, and N(CF3)2 in various combinations) hydrophosphoryl compounds and their complexes with water molecules formed with the participation of H-bonds of various types. Electron donor substituents were shown to stabilize the oxide form (IIIa), and electron acceptor substituents, the phosphinuos acid form (IIIb). The induction and resonance effects were found to be approximately equally significant, which was in agreement with the available experimental data. Oxides IIIa with donor substituents R and R’ formed the strongest H-bonds with water molecules coordinated at the phosphoryl group oxygen atom, which additionally stabilized these forms compared with their tautomers IIIb. At the same time, phosphinuos acids RR’POH (IIIb) with acceptor substituents more readily acted as H-bond donors with respect to water molecules and formed coordination bonds with water oxygens, which shifted tautomeric equilibria toward them. Intramolecular hydrogen transfer was shown to be forbidden in tautomeric equilibria. A description of these equilibria therefore required using other models with the participation of proton donor molecules as carriers or hydrophosphoryl compound dimers.

Specific and non-specific influence of the environment on dihydrogen bonding and proton transfer to [RuH 2{P(CH 2CH 2PPh 2) 3}

The proton transfer from substituted phenols (ArOH = p-nitrophenol, p-nitophenyl-aza-phenol) to the ruthenium dihydride complex [(PP 3)RuH 2], where PP 3 = P(CH 2CH 2PPh 2) 3, was studied by variable temperature UV–visible spectroscopy in dichloromethane, THF, THF/CH 3OH and THF/CH 3CN mixtures, showing a significant influence of the polarity and/or the proton donating/proton accepting properties of the solvent on the position of the proton transfer equilibrium. The formation of ion pairs stabilized by hydrogen bonding between the non-classical cation [(PP 3)RuH(η 2-H 2)] + and the homoconjugated anion [ArOHOAr] − was determined in low-polar media. The increase of the media polarity has been proved to favor the proton transfer leading to the dissociation of hydrogen bonded ion pairs [{(PP 3) RuH(η 2-H 2)} +⋯{ArOHOAr} −]. Under comparable media polarity, the presence of a protic solvent in the mixture greatly favors the proton transfer due to the additional H-bonding with solutes. The structural, energetic and electronic features of the dihydrogen bonded adducts and of the proton transfer products were investigated by means of DFT/B3LYP calculations on the model dihydride [{P(CH 2CH 2PH 2) 3}RuH 2] using CH 3OH or CF 3OH as proton donors. The specific and non-specific influence of the media properties on the dihydrogen bonding and proton transfer was studied by introducing the second protic (proton donor or solvent) molecule in the model system or by CPCM calculations. The additional participation of external molecules, from either the solvent or the alcohol, strengthens remarkably the dihydrogen bonded adducts and eases the proton transfer process.