Miquel Moreno

• PhD
• Autonomous University of Barcelona

Numerical simulations of the absorption bands of photoswitch E-o-tetrafluoroazobenzene in DMSO solution under one-, two-, and three-photon absorption conditions combined with the analysis of the behavior of transition probability under distortion of planarity reveal many similarities between the mono- and triphoton spectroscopic behaviors with a tw...

To interrogate neural circuits and crack their codes, in vivo brain activity imaging must be combined with spatiotemporally precise stimulation in three dimensions using genetic or pharmacological specificity. This challenge requires deep penetration and focusing as provided by infrared light and multiphoton excitation, and has promoted two‐photon...

To interrogate neural circuits and crack their codes, in vivo brain activity imaging must be combined with spatiotemporally precise stimulation in three dimensions using genetic or pharmacological specificity. This challenge requires deep penetration and focusing as provided by infrared light and multiphoton excitation, and has promoted two‐photon...

Simulations based on molecular dynamics coupled to excitation energy calculations were used to generate simulated absorption spectra for a family of halide derivatives of azobenzene, a family of photoswitch molecules with a weak absorption band around 400–600 nm and potential uses in living tissue. This is a case where using the conventional approa...

In order to theoretically design multi-state photoswitches with specific properties, an exhaustive computational study is first carried out for an azobenzene dimer that has been recently synthesized and experimentally studied. This study allows for a full comprehension of the factors that govern the photoactivated isomerization processes of these m...

Metal-organic frameworks (MOFs) are being developed for a variety of applications ranging from gas storage and separation, photocatalysis, sensing and lighting to drug delivery and water capture. In relevance to...

Shape-persistent phenylene-ethynylene macrocycles are being intensively studied since that they are being used for making hydrogen-bonded organic frameworks (HOFs). Here, we report on studies of two expanded macrocycles: Ex-COOH and Ex-COOMe (its methyl ester), in solutions, and in solid state (HOF Ex-apo and Ex-ester, respectively). For Ex-COOH, t...

Hexaazatriphenylene (HAT) derivatives are being used for the fabrication of hydrogen-bonded organic frameworks (HOFs). Here, we report on studies of two HAT derivatives: CBPHAT and its butylated partner, CBPHAT-C4H9, in N-N-dimethylformamide (DMF) solutions, and in solid state. CBPHAT displays no planar conformations, and different species when int...

Large efforts are currently devoted to design molecular photoswitches with specific properties. In this sense a recent publication [J. Am. Chem. Soc. , 2015, 137, 14982-14991] has synthesized and analyzed the photochromic properties a large set of acylhidrazones (ACHs), a relatively unexploited class of potential photoswitches with two stable (E an...

We report on optical studies of a boron-dipyrromethene (BODIPY) based conjugated microporous polymer, CMPBDP, being a promising material for applications in photonic devices, and on two related model dyes (MD1 and MD2). We used time-resolved fluorescence spectroscopy and theoretical calculations to elucidate the photobehavior of the three material...

Manipulation of neuronal activity using two-photon excitation of azobenzene photoswitches with near-infrared light has been recently demonstrated, but their practical use in neuronal tissue to photostimulate individual neurons with three-dimensional precision has been hampered by firstly, the low efficacy and reliability of NIR-induced azobenzene p...

We report on the excited-state behavior of proton transfer phenanthroimidazole derivatives, such as HPPI and NMHPPI, in solutions, using steady-state and femto- to nanosecond time-resolved fluorescence spectroscopy. The experimental observation is supported by theoretical calculations (TDDFT). In DCM and ACN undertake two different paths for the ex...

We report quantum mechanical/molecular mechanical non-adiabatic molecular dynamics simulations on the electronically excited state of Green Fluorescent Protein mutant S65T/H148D. We examine the driving force of the ultrafast (τ < 50 fs) excited-state proton transfer unleashed by absorption in the A band at 415 nm and propose an atomistic descriptio...

The dianions formed by electroreduction of Z-O2NC6H4CH=CHC6H4NO2, E-O2NC6H4CH=CHC6H4NO2, O2NC6H4CH2=CH2C6H4NO2 or O2NC6H4CMeH-CMeHC6H4NO2, as well as the anion radical arising from 4-nitrotoluene are stable,in the time scale of the cyclic voltammetry (DMF+0.10 M NBu4BF4). However, in the electrolysis time scale (from minutes to hours), only the dia...

In this work, we report on the results of theoretical and experimental studies of a serie of Dehydrobenzoannulene (DBA) derivatives (Nu-T12 [5,6,11,12,17,18-hexadehydrotribenzo[a,e,i]cyclododecene], T12-COOMe [5,6,11,12,17,18-hexadehydro-2,3,8,9,14,15-hexakis(4-methoxycarbonylphenyl)tribenzo[a,e,i]cyclododecene] and T12-COOH [5,6,11,12,17,18-hexade...

Recently synthesized BF2-coordinated azoderivatives have been proposed as photoswitches that operate in the optical window (600-1200 nm) for use in bioimaging applications. In this work we have theoretically analyzed these compounds and modify some substituents in order to analyze what properties of the molecule govern its photochemistry. Our resul...

Extensive MD simulations combined with QM/MM calculations have been performed on mNeptune1 and mCardinal red fluorescent proteins to establish the reasons behind the red shift of the excitation wavelength of mCardinal with respect to mNeptune1. In both cases, it is seen that Arg197 stabilizes the chromophore but cannot be described as stabilizing p...

Classical molecular dynamics (MD) simulations are carried out for the recently developed TagRFP675 fluorescent protein (FP), which is specifically designed to fully absorb and emit in the near infrared (NIR) region of the electromagnetic spectrum. Since the X-ray data of TagRFP675 reveal that the chromophore exists in both the cis and trans configu...

Green fluorescent protein (GFP) mutant S65T/H148D has been proposed to host a photocycle that involves an excited-state proton transfer between the chromophore (Cro) and the Asp148 residue and takes place in less than 50 fs without a measurable kinetic isotope effect. It has been suggested that the interaction between the unsuspected Tyr145 residue...

We report on the spectroscopic and photodynamical behaviours of 5-amino-2-(2’-hydroxyphenyl)benzoxazole (5A-HBO) in different solutions. The dye exhibits an ultrafast ICT reaction (<50 fs) (comparable to that observed for its methylated derivative, 5A-MBO), in agreement with the results of TD-DFT theoretical calculations (gas phase). Depending on t...

In this paper we have analyzed the feasibility of spontaneous proton transfer in GFP at the Franck-Condon region directly after photoexcitation. Computation of a sizeable portion of the potential energy surface at the Franck-Condon region of the A structure shows the process of proton transfer to be unfavorable by 3 kcal mol−1 in S1 if no further s...

Green Fluorescent Protein (GFP) variant S65T/H148D recovers the A-band fluorescence lost in the single mutant S65T and it has been established that Asp148 is the alternate proton acceptor for the excited state proton transfer (ESPT). This mutant has been widely studied and presents unique spectroscopic properties, such as an ultrafast rise of the f...

Green Fluorescent Protein variant S65T/H148D has been reported to host a photocycle involving the photoinduced proton-transfer reaction between the chromophore and residue Asp148 under 50 fs and without measurable kinetic isotope effect, and experimental evidence is suggestive of the existence of a highly delocalized proton between these residues....

For a long time, low-barrier hydrogen bonds (LBHBs) have been proposed to exist in many enzymes and to play an important role in their catalytic function, but the proof of their existence has been elusive. The transient formation of an LBHB in a protein system has been detected for the first time using neutron diffraction techniques on a photoactiv...

A thorough analysis of the single and double proton transfer and the internal rotations of neutral indigo and its dianionic leucoindigo form has been performed for the ground and first singlet excited electronic states using, respectively, DFT and TDDFT state-of-the-art methods. Our theoretical analysis discloses that the diketo isomer is the most...

The synthesis of several dimeric silver compounds containing bis(pyrazol-1-yl)-6-(R)-s-triazine or bis(3,5-dimethylpyrazol-1-yl)-6-(R)-s-triazine ligands and coordinated triflate is described. The structures of two of the compounds have been determined by X-ray diffraction. Both derivatives show ligand-unsupported argentophilic contacts and differe...

The absorption spectrum of a fluorescent protein is determined by its chromophore, but the residues that surround it also have a remarkable role, leading to noticeable spectral shifts. We have theoretically analyzed the monomeric protein Keima (mKeima), a red fluorescent protein most remarkable for an outstanding difference between the absorption a...

Fluorescent proteins (FP) have become a major topic in the recent biochemical research due to their applications as in vivo markers in biological systems. In particular, Red fluorescent proteins (RFP) present some advantages since they require less harmful radiations to be excited and show less light-scattering. In this paper, we are focusing on th...

To determine the energetic feasibility of the mechanisms involved in the generation of the fluorescent species in red fluorescent proteins LSSmKate1 and LSSmKate2 developed by Piatkevich et al. ( Proc. Natl. Acad. Sci. U.S.A. 2010 , 107 , 5369 - 5374 and J. Am. Chem. Soc. 2010 , 132 , 10762 - 10770 ), a potential energy scan for the respective reac...

A reversible bidirectional ring-opening and ring-closing system triggered by electricity has been prepared by using metacyclophan-1-enes, a known thermo-photochromic molecular switch system.

The protonation with Brønsted acids HB (HBF4 and CF3CO2H) of [RuH2(arene)(PPh2Het)] derivatives (PPh2Het = dpim, Het = 2-N-methylimidazolyl; PPh2Het = PPh2py, Het = 2-pyridyl) that contain uncoordinated N atoms has been analyzed experimentally by NMR spectroscopy and through computational studies. Initially, at low temperature, the uncoordinated N...

The photophysics of N,N'-bis(salicylidene)-p-phenylenediamine (BSP) is analyzed both theoretically and experimentally. The alternative intramolecular proton-transfer reactions lead to three different tautomers. We performed DFT and TDDFT calculations to analyze the topography of the reactions connecting the three tautomers. Deactivation paths throu...

A theoretical study at a DFT level has been carried out on the pentafluorophenyl rotation in the compounds [Pd(C6F5)2(bpzmPh)] (1) and [Pd(C6F5)2(bpz*mPh)] (2) (bpzm = bis(pyrazol-1-yl)phenylmethane and bpz*mPh = bis(3,5-dimethylpyrazol-1-yl)phenylmethane). The orientation of one C6F5 with respect to the coordination plane was forced to adopt speci...

The effect of electron pair donor solvents on methylene reactivity has been theoretically studied by means of abinitio methods, using the split valence 3-21G basis set. The calculations have been done on the well-known methylene addition to ethylene, taking one water molecule in order to represent the donor solvent. We have shown that the process t...

Coupling between the proton motion and the internal degrees of freedom for intramolecular proton transfer in the hydrogen oxalate anion has been studied. A normal mode analysis at a sequence of points along the Intrinsic Reaction Coordinate (IRC) has been performed and the coupling functions Bk.F have been obtained. It is shown that, although for t...

Abinitio self-consistent field (SCF) calculations were done for a model of a ribonucleoside where only the ring part of the furanoside form of D-ribose is considered. Full geometry optimization and direct location of stationary points were used in order to characterize the geometry of the minimum energy structure and of the transition state for the...

A theoretical study on the reaction of proton transfer from ethanol to benzene anions was performed at the ab initio level. It was found that in the gas phase the reaction proceeds without potential energy barrier with respect to reactants held at infinite distance, even though a potential energy barrier exists when measured from the prebarrier com...

A method to compute probability current and its surface integral, the total flux, for systems of many particles of different masses is presented, based on transforming the wave function and its gradient onto a mass-weighted coordinate system. As a test for this methodology, it has been applied to a nontrivial 6-dimensional quantum dynamics study of...

A quantum electronic study of the effect of substituents on (2,2'-bipyridyl)-3,3'-diol and (2,2'-bipyridyl)-3,3'-diamine is presented. A large difference in the photochemical behavior between the original and the substituted selected systems is expected. For the sake of simplicity, the study is restricted to the symmetrically bi-substituted compoun...

The two isoelectronic bipyridyl derivatives [2,2'-bipyridyl]-3,3'-diamine (BP(NH(2))(2)) and [2,2'-bipyridyl]-3,3'-diol (BP(OH)(2)) are experimentally known to undergo very different excited-state double proton transfer processes that result in fluorescence quantum yields that differ by four orders of magnitude. Such differences have been theoretic...

The reaction of cycloaddition of ketene and cyclopentadiene presents experimentally a competing mechanism where the branching ratio between the Woodward–Hoffmann allowed [4+2] and forbidden [2+2] cycloaddition product is 4.56at −20°C, but because the minimum energy path misses the [2+2] product altogether, it has been claimed to lie beyond the scop...

The synthesis of several silver double helices containing bis(3,5dimethylpyrazolyl)-6-(R)-s-triazine ligands is described. The structure of two of them has been determined by X-ray difraction. Both derivatives represent the first reported examples of a new interaction mode for a triazine ring that involves a triazine N atom bridging two metal cente...

A dynamical study has been performed to determine from first principles the molecular volume of C(6)H(6) and C(6)D(6) in the gas phase, starting from a normal-mode analysis and using anharmonic potential energy profiles at DFT level to determine vibrational eigenfunctions for all 30 degrees of freedom and using a Monte Carlo procedure to determine...

The ultrafast proton transfer dynamics of salicylideneaniline has been theoretically analyzed in the ground and first singlet excited electronic states using density functional theory (DFT) and time-dependent DFT calculations, which predict a (pi,pi( *)) barrierless excited state intramolecular proton transfer (ESIPT). In addition to this, the phot...

The two isoelectronic bipyridyl derivatives [2,2'-bipyridyl]-3,3'-diamine and [2,2'-bipyridyl]-3,3'-diol are experimentally known to undergo very different excited-state double-proton-transfer processes, which result in fluorescence quantum yields that differ by four orders of magnitude. In a previous study, these differences were explained from a...

The operation of the proton wire in Green Fluorescent Protein has been simulated by quantum dynamics and considering the coupling to the protein environment by means of a bath of harmonic oscillators. The simulation consists of 36 explicit and fully quantum degrees of freedom: 6 degrees of freedom represent the configuration of the proton wire, whi...

In this paper an EVB-based method to describe the energetics of operation of arbitrary-length heterogeneous proton-wires is described. The method keeps the number of fittable parameters low by exploiting the idea of “protonation states”. The method is applied to describe the 3-proton proton-wire described in Green Fluorescent Protein (GFP), and two...

A nuclear quantum dynamical simulation of the proton shuttle operating in the green fluorescent protein has been carried out on a high-quality, high-dimensionality potential energy surface describing the photoactive pipi* excited state, and including motion of both the three protons and of the donor and acceptor atoms of the hydrogen bonds in a clo...

The energy profile for the tautomerization reaction of 1,4-dimethylanthrone in the first triplet electronic state obtained through electronic calculations (B3LYP/ 6-31G(d)) is used to calculate the rate constants for the process at a wide range of energies using a modified RRKM microcanonical statistical formalism that takes into account tunneling....

The ultrafast proton-transfer dynamics of 1-hydroxy-2-acetonaphthone has been theoretically analyzed in the ground and first singlet excited electronic states by density functional theory calculations and quantum dynamics. The potential energies obtained in the ground electronic state reveal that the proton-transfer process does not lead to a stabl...

The two isoelectronic bipyridyl derivatives, [2,2'-bipyridyl]-3,3'-diamine and [2,2'-bipyridyl]-3,3'-diol, are experimentally known to undergo very different excited-state double-proton-transfer processes, which result in fluorescence quantum yields that differ by four orders of magnitude. Herein, density functional theory (DFT), time-dependent DFT...

This chapter provides a review of the previous work done to theoretically analyze and understand the host-CD interactions and to study the chemical (and photochemical) reactivity inside the CD Cavities. The use of quantum electronic methods to study host-guest CD complexes is discussed. Analysis is provided on the use of more sophisticated quantum...

Photoenolization of 6,9-dimethylbenzosuberone (2) has been theoretically studied. DFT(B3LYP) calculations give geometries for the keto form in very good accord with X-ray diffraction data. The energies for the minima and transition-states reveal that the tautomerization is only possible in the T1 state. Dynamics of the tautomerization in T1 are stu...

The intramolecular proton-transfer reaction in 3-hydroxyflavone (3HF) is theoretically studied both in the ground (S0) and first singlet excited (S1) electronic states. In S0 the proton-transfer reaction is shown to be quite unfavorable at the DFT (B3LYP) level. However, the back proton transfer is found to be a feasible process with a small energy...

The proton-transfer dynamics in the aromatic Schiff base salicylidene methylamine has been theoretically analyzed in the ground and first singlet (pi,pi) excited electronic states by density functional theory calculations and quantum wave-packet dynamics. The potential energies obtained through electronic calculations that use the time-dependent de...

The green fluorescent protein proton wire operating upon photoexcitation of the internally caged chromophore is investigated by means of classical molecular dynamics and multiconfigurational electronic structure calculations. The structure of the proton wire is studied for the solvated protein, showing that the wire is likely to be found in a confi...

The hybrid configuration interaction singles/time dependent density functional theory approach of Dreuw and Head-Gordon [Dreuw, A.; Head-Gordon, M. J. Am. Chem. Soc. 2004, 126, 4007] has been applied to study the potential energy landscape and accessibility of the charge-transfer pipi* excited state in the dimer of 7-azaindole, which has been tradi...

The use of the phosphine PPh2py instead of PPh3 in complexes of the type [Cp*RuH(P)2] enormously alters the kinetic control of the proton-transfer reactions over this compound and its chemical behavior. The reaction at low temperature of [Cp*RuH(PPh2py)2], 2, with HBF4 gives as products the classical dihydride trans-[Cp*RuH2(PPh2py)2](BF4), 3 (1 eq...

To be able to propose experimental tests to distinguish elongated dihydrogen transition-metal complexes from compressed dihydride transition-metal complexes, a thorough density functional study of the electronic structure in combination with quantum nuclear dynamics calculations have been performed for complexes [Cp*Ru(H2PCH2PCH2(H2)]+ and [CpRe(CO...

The intramolecular proton transfer and the internal rotations of the 2-(2′hydroxyphenyl)-4-methyloxazole (HPMO) in the first electronically excited singlet state (S1) have been theoretically studied. Electronic calculations have been carried out within an all-single configuration interaction scheme (CIS). Time-dependent DFT (TDDFT) calculations hav...

Complex [CpIr(dmpm)H(2)](2+) (dmpm = bis(dimethylphosphino)methane) has been reported to display temperature-dependent spin-spin coupling constant ((1)J(HD)) and isotope effect on the (1)H NMR chemical shift (Deltadelta). A combined electronic structure density functional theory + quantum nuclear dynamics study is used to determine from first-princ...

Density functional theory along with the time-dependent formalism (TD-DFT) are used to directly localise the stationary points in the first singlet excited state of tropolone. The optimisation reveals that the equilibrium geometry of tropolone in the excited state is planar, a result that seems in contradiction with recent analysis using the high-r...

Variational transition state theory has been used to calculate the kinetic isotope effects affecting product ratios in the reaction between (1)O(2) and d(6)-tetramethylethylene. The minimum energy path on the potential energy surface for this process reaches a valley-ridge inflection point and then bifurcates leading to the two final products. Usin...

The photodissociation dynamics of [Ru(PH3)3(CO)(H)2] and cis-[Ru(PH3)4(H)2] is theoretically analyzed in the lowest two excited singlet states. Energies obtained through electronic density functional theory calculations that use the time-dependent formalism are fitted to analytical reduced two-dimensional potential energy surfaces (2D-PES). The met...

We present experimental and theoretical studies of the ring−chain tautomerism (H-atom transfer and cyclization) for 2-acetylbenzoic acid at both ground and electronically first excited states. 1H and 13C NMR studies in solution confirm the existence of equilibrium between the open and ring structures at the ground state, with the ring one being dom...

Density functional theory and quantum dynamics simulations have been used to study the double-proton transfer reaction in 2,2'-bipyridyl-3,3'-diol in the first singlet excited electronic state. This process is experimentally known to be branched: It consists of a fast, concerted reaction mechanism (tau approximately 100 fs) and a stepwise reaction...

The proton transfer from the green fluorescent protein chromophore to a nearby water molecule is studied by means of CASSCF, CASPT2 and TDDFT calculations. A 1πσ* electronic state is found to intersect with the photoactive 1ππ* electronic state along the proton transfer coordinate. This state crossing constitutes a possible non-radiative deactivati...

Reaction of [Cp*Ir(P-P)Cl][B(C6F5)4] (P-P = bisdimethydiphosphinomethane (dmpm), bisdiphenyldiphosphinomethane (dppm)) with [Et3Si][B(C6F5)4] in methylene chloride under 1 atm of hydrogen gas affords the dicationic compressed dihydride complexes [Cp*Ir(P-P)H2][B(C6F5)4]2. These dicationic complexes are highly acidic and are very readily deprotonate...

The ultrafast enolketo photoisomerization in the lowest singlet excited state of 2-(2`-hydroxyphenyl)-4-methyloxazole (HPMO) is investigated using classical molecular dynamics in conjunction with an empirical valence bond potential. This process is studied in four different environments: the gas phase, dimethyl sulfoxide, water, and human serum alb...

The photoenolization of 1,4-dimethylanthrone (1,4-MAT) and 1,4-dimethylanthrone-d8 (1,4-DMAT) in the gas phase and in 2,2,2-trifluoroethanol (TFE) has been studied theoretically in this work. An electronic energy profile with minima and saddle-point structures is determined by density functional theory methods in the ground state (S0) and in the tr...

In this article a wide variety of computational approaches (molecular mechanics force fields, semiempirical formalisms, and hybrid methods, namely ONIOM calculations) have been used to calculate the energy and geometry of the supramolecular system 2-(2'-hydroxyphenyl)-4-methyloxazole (HPMO) encapsulated in beta-cyclodextrin (beta-CD). The main obje...

A systematic study of the proton transfer in the 7-azaindole–water clusters (; n=1–4) in both the ground and first excited singlet electronic states is undertaken. DFT(B3LYP) calculations for the ground electronic state shows that the more stable geometry of the initial normal tautomer presents a cyclic set of hydrogen bonds that links the two nitr...

The photodissociation dynamics of [Ru(PH3)3(CO)(H)2] complex in the lowest two singlet excited electronic states has been theoretically analyzed. Reduced two-dimensional potential energy surfaces (PES) are built up by combining a time-dependent method to calculate the excited states energy with DFT (B3LYP) electronic calculations of the ground stat...

In this work we have theoretically studied the splittings experimentally observed in 5-methyl tropolone in the first excited singlet state, S1. Tropolone shows a vibrational level splitting due to delocalization of the wave function over the symmetric potential energy double well in the proton-transfer coordinate. This splitting dramatically decrea...

The Herman–Kluk initial value representation semiclassical approach has been applied, and proven effective, as well as accurate, to account for the intriguing elongated dihydrogen structure in a ruthenium coordination complex. Results are satisfactory even though the reduced dimensionality two-dimensional potential, involving the relevant distances...

Ab initio full geometry optimizations were carried out for the ground and first excited singlet electronic states of the 7-azaindole base pair. Results indicate that the excited state has to be described as a dimer of an excited base unit and another one in the ground state. This asymmetry leads to an asynchronic double proton transfer process that...

In this work we have theoretically studied the splittings experimentally observed in 5-methyltropolone in the first excited singlet state, S1. Tropolone shows a vibrational level splitting due to delocalization of the wave function over the symmetric potential energy double well in the proton transfer coordinate. This splitting decreases dramatical...

Some photocromic compounds involve photoinduced intramolecular proton transfer (PIPT) as a consequence of a fast electronic redistribution due to electronic excitation. In this study, we have examined the PIPT that occurs in 2-(2′-hydroxyphenyl)-4-methyloxazole (HPMO) in gas phase and encapsulated in β-cyclodextrin (β-CD). An hybrid method has been...

This chapter describes that transition-metal polyhydride complexes are remarkable for a number of reasons. Most of them are related to the peculiar chemical properties of the metal-hydride combination. There are, however, some specific phenomena in the behavior of these chemical compounds that cannot be explained through “conventional” chemistry co...

Two different dianionic species, close in energy, result from the electroreduction of 2,2'-4,4'-tetranitrobiphenyl, 1. The first-formed species has biradical characteristics, such as a triplet EPR spectrum, but it slowly evolves to another EPR-silent species, essentially described as a quinoid form. DFT calculations also support the existence of tw...

DFT electronic calculations are performed for the double proton transfer in bicyclic oxalamidines 2,2′-bis-(3,4,5,6-tetrahydro-1,3-diazine) (OA6) and 2,2′-bis-(4,5,6,7-tetrahydro-1,3-diazepine) (OA7). Bidimensional potential energy surfaces retaining the characteristics of the stationary points located in the whole potential are built to calculate...

Experimental determination of the equilibrium isotope effect for the dihydride/dihydrogen tautomerism (EIET) in the Kubas complex W(CO)3(PCy3)2(η2-H2) has not yet been achieved because of the lack of vibrational frequencies for the dihydride form. Even so, Bender, Kubas, Hoff, and co-workers3 have estimated a normal EIET, which predicts that deuter...

In this paper ab initio full geometry optimizations are carried out for the ground and first excited singlet electronic states of the 7-azaindole dimer, a well-known prototype of the DNA base pairs. Results indicate that the C2h symmetry of the ground-state minimum energy is not maintained in the excited state that has to be described as a dimer be...

Ab initio calculations at the S0 state of 1-hydroxy-2-acetonaphthone reveal the existence of several conformers that result from the hydroxyl and acetyl groups rotation and a coupled proton-transfer and twisting motion on the potential-energy surface. The most stable structure has an O–H...O=C internal H-bond. The bulk effect on the stability of th...

The internal rotational motion, the intramolecular proton-transfer reaction, and the subsequent internal twisting process of 1-hydroxy-2-acetonaphthone (HAN) are studied in the first singlet excited electronic state (S1) using the ab initio electronic-structure method at the CIS/6-31G** level. The calculations show a multiple-well potential-energy...

Dihydrogen elimination from the reaction of the niobocene trihydride Cp‘2NbH3 (Cp‘ = η5-C5H4SiMe3) and the appropriate borane provides a synthetic route to the new borate-containing niobocene complexes [Nb(η5-C5H4SiMe3)2(η2-H2BR2)] (R2 = O2C6H4 (1), C8H14 (2), H2 (3)). The reaction with H2BO2C6H4 or H2BC8H14 proceeds at mild temperature, and the BH...

Equilibrium isotope effects (EIE) on the binding of H2 and D2 to transition metal complexes are calculated for a modeled version of W(CO)3(PCy3)2(η2-H2), [Ru(H···H)(C5Me5)(dppm)]+ and trans-[Os(H···H)Cl(dppe)2]+. Being probably unsatisfactorily described by the harmonic approach (specially in the elongated dihydrogen complexes), the thermodynamic c...