Analysis Of Electron Localization Function Research Articles

3+2] cycloaddition reaction between CF3-substituted thiocarbonyl ylides and thioketones: Exploration of regioselectivity and mechanistic aspects using Molecular Electron Density Theory

A CF3-containing thiadiazole derivative, TDA1, participates in a domino process initialized with a thermal N2 extrusion experienced at TDA1 within a retro- [3+2] cycloaddition (32CA) reaction to yield CF3-substituted thiocarbonyl ylide TCY3. Then, TYC3 is trapped over the course of a subsequent 32CA reaction toward thioketone TBP4 to generate dithiolane derivative CA5. This domino process was studied through Molecular Electron Density Theory (MEDT) at the B3LYP/6-31G(d) computational level. Exploration of the relative Gibbs free energies obviously indicates that this domino process needs to overcome high barriers justifying why the harsh conditions (100 °C for 24h in toluene) is experimentally requested. In excellent agreement with the experimental findings, an entirely C1–C5 regioselective, polar, and pmr-type 32CA reaction of in situ generated TCY3 toward TBP4 leads to the formation of cycloadduct CA5 as the sole product along a quite irreversible pathway. While the high global electrophilicity ω index of TBP4 together with the high global nucleophilicity N index of TCY3 are responsible for the considerable polar character of the mentioned 32CA reaction, analysis of the electrophilic Pk+ and nucleophilic Pk− Parr functions at the reactive sites of reactants allows to rationalize C1–C5 regioselectivity observed experimentally. In terms of quantum topological analysis of the electron localization function (ELF) over some relevant points located along the IRC profile connecting separate TCY3 and TBP4 to CA5, a non-concerted two-stage one-step molecular mechanism is established for this polar pmr-type 32CA reaction. Such ELF analysis evidently shows that formation of the first C1–C5 and second C3–S4 single bonds is a direct consequence of coupling C1- to –C5 and C3- to –S4 pseudoradical centers, respectively.

A molecular electron density theory study of the chemo- and regioselective [3 + 2] cycloaddition reactions between trifluoroacetonitrile N-oxide and thioketones

The [3 + 2] cycloaddition (32CA) reaction between trifluoroacetonitrile N-oxide (NO 7) and 2,2,4,4-tetramethyl-3-thioxocyclobutan-1-one (THK 12) as well as the self-dimerization of NO 7 as a competitive pathway were studied within the Molecular Electron Density Theory (MEDT) using several DFT functionals together with def2-TZVP basis set. Taking CCSD(T)/TZVP activation energies as reference, among the employed functionals, just the B2PLYP-D3(BJ) one is able to portray complete predominance of 32CA reaction over self-dimerization process in excellent agreement with the experimental outcomes. Analysis of the global reactivity indices permits to characterize NO 7 and THK 12 as a strong electrophile and a strong nucleophile, respectively, while analysis of the Parr functions allows explaining the chemo- and regioselectivity observed experimentally. The electron localization function (ELF) analysis of several points along the IRC profile associated with the energetically most favorable reaction channel permits to establish a non-concerted two-stage one-step molecular mechanism for this polar pmr-type 32CA reaction.

Insight into wild-type and T1372E TET2-mediated 5hmC oxidation using ab initio QM/MM calculations.

Ten-eleven translocation 2 (TET2) is an Fe/α-ketoglutarate (α-KG) dependent enzyme that dealkylates 5-methylcytosine (5mC). The reaction mechanism involves a series of three sequential oxidations that convert 5mC to 5-hydroxy-methylcytosine (5hmC), 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC). Our previous biochemical and computational studies uncovered an active site scaffold that is required for wild-type (WT) stepwise oxidation (Nat. Chem. Bio., 13, 181). We showed that the mutation of a single residue, T1372 to some amino acids, such as Glu, can impact the iterative oxidation steps and stop the oxidation of 5hmC to 5fC/caC. However, the source of the stalling at the first oxidation step by some mutant TET proteins still remains unclear. Here, we studied the catalytic mechanism of oxidation of 5hmC to 5fC by WT and T1372E TET2 using an ab initio quantum mechanical/molecular mechanical (QM/MM) approach. Our results suggest that the rate limiting step for WT TET2 involves a hydrogen atom abstraction from the hydroxyl group of 5hmC by the ferryl moiety in the WT. By contrast, our calculations for the T1372E mutant indicate that the rate limiting step for this variant corresponds to a second proton abstraction and the calculated barrier is almost twice as large as for WT TET2. Our results suggest that the large barrier for the 5hmC to 5fC oxidation in this mutant is due (at least in part) to the unfavorable orientation of the substrate in the active site. Combined electron localization function (ELF) and non-covalent interaction (NCI) analyses provide a qualitative description of the evolution of the electronic structure of the active site along the reaction path. Energy decomposition analysis (EDA) has been performed on the WT to investigate the impact of each MM residue on catalytic activity.

Hydrogen detachment driven by a repulsive 1πσ* state - an electron localization function study of 3-amino-1,2,4-triazole.

Electron localization function analysis reveals the details of a charge induced hydrogen detachment mechanism of 3-amino-1,2,4-triazole, identified recently to be responsible for phototautomerization of the molecule. In this process vertical excitation to the 1πσ* state is followed by the barrier-less migration of a H atom along the N-H bond toward the conical intersection with the S0 ground state. The most striking feature revealed for the 1πσ* state is partial ejection of σ* electrons outside the molecule, even beyond the NH group, at the Franck-Condon point. Further gradual spatial localization of the electron around the proton moving along the N-H stretching coordinate gives a plausible explanation for the repulsive character of the 1πσ* potential energy surface with the proton wading through the region of space where some negative charge is accumulated ('a virtual acceptor'), dragging some electron density. This mechanism resembles the one postulated for the hydrogen transfer from a donor molecule (D-H) to an acceptor one (A) in a class of vertically excited molecules with a preexisting inter- or intramolecular D-HA motif, even though the acceptor molecule is absent. The present analysis demonstrates also that the bond evolution and changes in the electron density along the excited state reaction path can be effectively studied with the use of an electron localization function.

A quantum‐chemical DFT study of the mechanism and regioselectivity of the 1,3‐dipolar cycloaddition reaction of nitrile oxide with electron‐rich ethylenes

AbstractThe 1,3‐dipolar cycloaddition (13DC) reactions of nitrile‐oxide NO 1 with two ethylenes, enamine 2a and enamine 2b, were computationally studied using B3LYP/6‐31G(d) DFT methods. The two possible ortho and meta regioselective channels were characterized and analyzed. The moderate polarity of these 13DC reactions is related to the high nucleophilic character of both ethylenes, and the moderate electrophilic nature of the NO 1, that accounts for the relatively low calculated activation energies. Analysis of different forms of energies along the different reaction channels indicates that the present 13DC reactions are completely ortho regioselective, accordingly to the experimental outcomes. Electron localization function analysis indicates that these 13DC reactions proceed via a nonconcerted (two‐stage) one‐step mechanism.

Structural and electronic properties of MnSi under high pressure: A first-principles calculation

To explore the structure and phase stabilities of transition metal silicides under high pressure, we report a systematic study of the high-pressure structural evolution of MnSi using the CALYPSO structure searching method and first-principles calculations. A novel cubic Pm-3m-structured MnSi with a MnSi8 cube environment is uncovered. Upon increasing the pressure to 41.91GPa, the cubic ε-FeSi-type MnSi transforms into a CsCl structure. Both the ε-FeSi and CsCl phases are shown to be mechanically and dynamically stable. The density of states, electron localization function and Bader charge analysis suggest that both phases of MnSi possess dominant covalent bonding character.

A DFT Study of the Conversion of Ptaquiloside, a Bracken Fern Carcinogen, to Pterosin B in Neutral and Acidic Aqueous Medium

AbstractThe conversion of ptaquiloside (PtQ), a bracken fern (Pteridium aquilinum) carcinogen, to pterosin B (PtB), which is involved in the underlying mechanisms of PtQ genotoxicity and carcinogenicity, has been theoretically studied in aqueous neutral (AN) and acid (AA) media, using DFT methods at the PCM(water)‐B3LYP/6‐31G(d)//B3LYP/6‐31G(d) computational level. The β‐elimination of glucose in AN and four reactive channels (A‐D) defined by as many protonation sites in PtQ were calculated. Activation enthalpy decreases (from 42.0 to 12.6 kcal mol−1) in AA relative to AN suggesting protic catalysis. The most favoured channel A started with protonation of the tertiary O15 hydroxyl of PtQ and SN1 water release with strong stabilisation by the spirocyclopropane ring. Natural population analysis and electron localisation function analysis showed significant electron depopulation of vicinal C−C bonds and the remarkable leaving character of the quaternary carbon, which enhanced the nucleophilic attack of water on the distal methylenes while the glucose fragment was retained. This intermediate was unstable, degrading rapidly to a stable PtB‐glucose‐water‐H+ molecular complex whose calculated electronic spectrum (λmax=271.5 nm) matched the value of an intermediate reported earlier with a different structure. PtQ‐dienone, long assumed as the carcinogenic form of PtQ, is not formed in AA but only and unfavourably so in protonated form assisted by one molecule of water.

Characterisation of the reaction mechanism between ammonia and formaldehyde from the topological analysis of ELF and catastrophe theory perspective

A prototypical reaction between ammonia and formaldehyde has been investigated at the DFT(M06)/6-311++G(d,p) computational level using the Bonding Evolution Theory (BET). BET is a very useful tool for studying reaction mechanisms as it combines topological analysis of electron localisation function with the catastrophe theory. Each of two studied reactions: H2C=O + NH3 ↔ HO–C(H2)–NH2 (hemiaminal) and HO–C(H2)–NH2 ↔ HN = CH2 (Schiff base) + H2O consists of six steps. Formation of hemiaminal starts from a nucleophillic attack of nitrogen lone pair in NH3 on the carbon atom in H2C=O and is subsequently followed by hydrogen transfer within the N–H..O bridge. A Schiff base is formed via the dehydration reaction of the hemiaminal, where the C–O bond is broken first, followed by hydrogen transfer towards the [HO]δ− moiety, resulting in water and methanimine. The present paper focuses on differences in reaction mechanisms for the processes described above. The results have been compared to the reaction mechanism for stable hemiaminal synthesis from benzaldehyde and 4-amine-4H-1,2,4-triazole studied previously using the BET theory.

BET & ELF Quantum Topological Analysis of Neutral 2-Aza-Cope Rearrangement of γ-Alkenyl Nitrones.

The 2-Aza-Cope rearrangement of γ-alkenyl nitrones is a rare example of the neutral thermal 2-aza-Cope process that usually takes place with cationic species. During the rearrangement, a redistribution of bonds and electronic density occurs in one kinetic step. However, the introduction of substituents with different steric requirements and electronic features might alter the activation energies and the synchronicity of the reaction. The electron localization function (ELF) analysis and its application to Bonding Evolution Theory (BET) analysis within the context of Molecular Electron Density Theory (MEDT) is an excellent tool to monitor the electron density along the reaction coordinate and thus investigate in detail bond breaking and formation and the corresponding energy barriers. By analyzing topological ELF calculations of seventeen 2-aza-Cope nitrone rearrangements with selected substituents, the main factors influencing the synchronicity of the process were investigated. This MEDT study results revealed that the rearrangement is a non-polar process mostly influenced by steric factors rather than by electronic ones, and confirms the pseudoradical character of the process rather than any pericyclic electron-reorganization.

Mechanism study on the copper-free click reaction of a coumarin-conjugated cyclooctyne

The mechanism of a bioortogonal click reaction between 2-azidoethanol and coumBARAC has been examined using DFT methods at B3LYP/6-31G(d,p) and M06-2X/6-31G(d,p) computational levels. The regiochemistry of the reaction has been studied based on potential energy surface analysis and global reactivity indices of the reactants. The global electron density transfer (GEDT) calculations at the possible transition states (TSs) revealed that this cycloaddition (CA) has a nearly non-polar character. The strain and electronic effects on the reactivity of coumBARAC with 2-azidoethanol was studied using distortion/interaction transition state model and compared with CA reaction of this dipole with phenylacetylene as a strain-free reaction. The IRC calculations and the topological electron localization function (ELF) analysis explain properly the one-step two-stage mechanism of this strain-promoted CA reaction, as well as the effects of the strain on the electronic structure of cycloalkynes and the activation energy barriers of CA reactions. By application of bonding evolution theory (BET), nine successive domains of structural stability have been recognized along the reaction path, as well as the bifurcation catastrophes responsible for the changes in the topology of the system.

Investigation of structural and multiferroic properties of three phases of BiFeO3 using modified Becke Johnson potential technique

Electronic band structure, ferroelectric and ferromagnetic properties of Cubic, Tetragonal and Rhombohedral (hexagonal axis) phases of multiferroic BiFeO3 compound has been investigated using first-principles calculations under the generalized gradient (GGA) and TB-mBJ semi local (Tran-Blaha modified Becke-Johnson) potential approximations using WIEN2k code. For this purpose, the total energies were calculated as a function of reduced volumes and the data were fitted to Brich Murnaghan equation. The estimated ground state parameters are found to be comparable with those of experimental ones. The semiconducting behavior of the material was obtained using TB-mBJ method in the spin polarized mode. Analysis of the density of states indicates that the valence band consists of Fe-d and O-p states, while the conduction band is composed of Fe-d and Bi-p states. The analysis of electron localization function shows that stereochemically active lone-pair electrons are present at Bi sites of Rhombohedral and Tetragonal phases and are responsible for the displacements of Bi atoms from the centro-symmetric to the non-centrosymmetric structure leading to the exhibition of ferroelectricity. Further, it has been concluded that the “lone pair” may have been formed due to the hybridization of 6s and 6p atomic orbitals with 6s2 electrons filling one of the resulting orbitals in Bi. The Polarization and the magnetic properties including susceptibility were obtained. The calculated magnetic moments at the iron sites are not integer values, since Fe electrons have a hybridization interaction with the neighboring O ions.

Theoretical analysis of the binding of iron(III) protoporphyrin IX to 4-methoxyacetophenone thiosemicarbazone via DFT-D3, MEP, QTAIM, NCI, ELF, and LOL studies.

Thiosemicarbazones display diverse pharmacological properties, including antimalarial activities. Their pharmacological activities have been studied in depth, but little of this research has focused on their antimalarial mode of action. To elucidate this antimalarial mechanism, we investigated the nature of the interactions between iron(III) protoporphyrin IX (Fe(III)PPIX) and the thione-thiol tautomers of 4-methoxyacetophenone thiosemicarbazone (MAPTSC). Dispersion-corrected density functional theory (DFT-D3), the quantum theory of atoms in molecules (QTAIM), the noncovalent interaction (NCI) index, the electron localization function (ELF), the localized orbital locator (LOL), and thermodynamic calculations were employed in this work. Fe(III)PPIX-MAPTSC binding is expected to inhibit hemozoin formation, thereby preventing Fe(III)PPIX detoxification in plasmodia. Preliminary studies geared toward the identification of atomic binding sites in the thione-thiol tautomers of MAPTSC were carried out using molecular electrostatic potential (MEP) maps and conceptual DFT-based local reactivity indices. The thionic sulfur and the 2 N-azomethine nitrogen/thiol sulfur of, respectively, the thione and thiol tautomers of MAPTSC were identified as the most favorable nucleophilic sites for electrophilic attack. The negative values of the computed Fe(III)PPIX-MAPTSC binding energies, enthalpies, and Gibbs free energies are indicative of the existence and stability of Fe(III)PPIX-MAPTSC complexes. MAPTSC-Fe(III) coordinate bonds and strong hydrogen bonds (N-H···O) between the NH2 group in MAPTSC and the C=O group in one propionate side chain of Fe(III)PPIX are crucial to Fe(III)PPIX-MAPTSC binding. QTAIM, NCI, ELF, and LOL analyses revealed a subtle interplay of weak noncovalent interactions dominated by dispersive-like van der Waals interactions between Fe(III)PPIX and MAPTSC that stabilize the Fe(III)PPIX-MAPTSC complexes.

Covalent Co-O-V and Sb-N Bonds Enable Polyoxovanadate Charge Control.

The formation of [{CoII(teta)2}{CoII2(tren)(teta)2}VIV15SbIII6O42(H2O)]·ca.9H2O [teta = triethylenetetraamine; tren = tris(2-aminoethyl)amine] illustrates a strategy toward reducing the molecular charge of polyoxovanadates, a key challenge in their use as components in single-molecule electronics. Here, a V–O–Co bond to a binuclear Co2+-centered complex and a Sb–N bond to the terminal N atom of a teta ligand of a mononuclear Co2+ complex allow for full charge compensation of the archetypal molecular magnet [V15Sb6O42(H2O)]6–. Density functional theory based electron localization function analysis demonstrates that the Sb–N bond has an electron density similar to that of a Sb–O bond. Magnetic exchange coupling between the VIV and CoII spin centers mediated via the Sb–N bridge is comparably weakly antiferromagnetic.

A DFT computational study on the molecular mechanism of reaction between pyridinium salts and π-deficient ethylenes: Why furan derivatives are formed instead of feasible cyclopropane derivatives and [3 + 2] cycloadducts?

The reaction between 1-(2-amino-2-oxoethyl)pyridinium ylide 4 (PY4) and 1-methylene-3,4-dihydronaphthalen-2(1H)-one 5 (MDN5) in the presence of acetonitrile (CH3CN) was theoretically studied at the M06-2X/6-31G(d,p) computational level. Calculated relative Gibbs free energies indicate that encounters between PY4 and MDN5 in the reaction mixture result in the formation of the highly zwitterionic betaine-like intermediate IM1ca in an entirely C1C5 regio- and a cisoid-anti stereoselective manner over the course of a Michael addition reaction through a very low barrier (4.2kcal/mol) and a highly exergonic (24.7kcal/mol) pathway. While C1C5 regioselectivity can be rationalized via the analysis of the computed nucleophilic and electrophilic Parr functions at the reactive sites of reagents, the cisoid-anti stereoselectivity predominance over the cisoid-syn one can nicely be portrayed within the non-covalent interactions (NCIs) analysis at the cisoid-anti transition state TS1ca and cisoid-syn transition state TS1cs involved in the Michael addition reaction. The electron-localization function (ELF) quantum topological analysis obviously demonstrates that the C1 carbon atom in PY4 exhibits a pseudoradical character indicating the high reactivity of PY4 toward C5 electrophilic attack of MDN5 which is characterized with a very low barrier associated with the C1C5 single bond formation along the Michael addition step. Upon formation of IM1ca, in excellent agreement with the experimental outcomes, an SNi-like reaction converts IM1ca into trans-furan derivative 8 together with pyridine via a high barrier (23.9kcal/mol) but a highly irreversible pathway making compound 8 as the only reachable product under “thermodynamically-controlled” conditions (refluxing over 8h). In other words, neither [3+2] cycloadduct 6 (as the kinetically most favourable but thermodynamically most unfavourable product) nor cyclopropane derivative 7 (as both kinetically and thermodynamically most undesirable product) can be obtained under the reaction conditions. From the molecular mechanism point of view, the ELF analyses indicate that while C1C5 single bond formation within the Michael addition reaction takes place via a C- to -C coupling of two pseudoradical C1 and C5 centers, formation of C1O8 single bond accompanied with the C1N15 single bond breaking at the generated IM1ca to afford compound 8 is a direct consequence of donation of some electron density of O8 oxygen lone electron pairs to the C1 carbon atom.

Double and Triple Si-H-M Bridge Bonds: Matrix Infrared Spectra and Theoretical Calculations for Reaction Products of Silane with Ti, Zr, and Hf Atoms.

Infrared spectra of matrix isolated dibridged Si(μ-H)2MH2 and tribridged Si(μ-H)3MH molecules (M = Zr and Hf) were observed following the laser-ablated metal atom reactions with SiH4 during condensation in excess argon and neon, but only the latter species was observed with titanium. Assignments of the major vibrational modes, which included terminal MH, MH2 and hydrogen bridge Si-H-M stretching modes, were confirmed by the appropriate SiD4 isotopic shifts and density functional vibrational frequency calculations (B3LYP and BPW91). The Si-H-M hydrogen bridge bond is calculated as weak covalent interaction and compared with the C-H···M agostic interaction in terms of electron localization function (ELF) analysis and noncovalent interaction index (NCI) calculations. Furthermore, the different products of Ti, Zr, and Hf reactions with SiH4 are discussed in detail.

Pressure-induced boron nitride nanotube derivatives: 3D metastable allotropes

The high-pressure behaviors of large-diameter single-walled boron nitride nanotubes (BNNTs) are studied by the first-principles method. One sp3-hybridized and three sp2/sp3-hybridized BN allotropes are obtained via compressing large diameter BNNTs. Due to the restricted movement of nonequivalent B and N atoms, the large BN nanotubes have a chance to form B-B and N-N bonds between intertubes under pressure, in addition to the common B-N bonds. The electron localization function and Mulliken's population analysis indicate the covalent nature of the B-B and N-N dimers. The electronic band structure and density of state calculations show a local conducting feature of tP24-BN and superhard semiconducting character of the other three allotropes with indirect band gaps of 1.28 – 3.13 eV.

Characteristics of the molecular electron density, delocalization effect and hydrogen bonding interaction of nitroxoline

The density functional theoretical (DFT) calculations have been carried out at the B3LYP/6-311G(d,p) level of theory for nitroxoline monomer and dimer molecule. The dimer molecule formed between two nitroxoline subunits has the largest stability, and is held together by two OH⋯N hydrogen bonds. Stability of the molecule arising from hyperconjugative interaction and intra/inter molecular charge transfer has been analyzed using natural bond orbital (NBO) analysis. The topological analysis of electron localization function (ELF) provides effect of delocalization. Quantum theory of atoms in molecule (QTAIM) has been applied to gain deep understanding to the existence of intra- and inter-molecular interaction.

Synthesis and Mechanical Character of Hexagonal Phase δ-WN.

In this work, high-quality bulk WC-structured WN (δ-WN) was synthesized via an untraditional method and the structure was accurately determined by X-ray diffraction and Rietveld refinement. In the process of synthesizing δ-WN, W2N3 and melamine were used as tungsten source and nitrogen source, respectively. The result of successfully synthesized high-quality δ-WN indicates that our method is an effective route for synthesizing high-quality bulk δ-WN and melamine is a pure nitrogen source for introducing the nitrogen to the metal precursor. The mechanical properties, bulk modulus, and Vickers hardness (HV) were first investigated by in situ high-pressure X-ray diffraction and Vickers microhardness tests, respectively. It is worth noting that the bulk modulus of δ-WN is 373 ± 8.3 GPa, which is comparable to that of c-BN. The Vickers hardness is 13.8 GPa under an applied load of 4.9 N. It is worth noting that W-W metallic bond and W-N ionic bond are mainly chemical bond in δ-WN based on the analysis of electron localization function (ELF), density of states (DOS), and Mulliken population. This result can well clarify that δ-WN is only a hard material for the lack of strong W-N covalent bonds to form 3D network structure. Our results are helpful to understand the hardness mechanism and design superhard materials in transition-metal nitrides.

Dimeric nature of N-coordinated Mg and Ca ions in metaloorganic compounds. The topological analysis of ELF functions for Mg–Mg and Ca–Ca bonds

The local electronic structure of the Mg–Mg and Ca–Ca bonds have been investigated in the model dimeric magnesium(I) and calcium(I) molecules: [C10H18Mg2N4], and [C10H18Ca2N4] using the topological analysis of Electron Localisation Function (ELF). The wave function has been approximated by the DFT method and PBE, B3LYP, M052X, M062X, ωB97XD, CAM-B3LYP, LC-ωPBE and B2PLYP functionals. The investigated bonds are covalent, and are represented by disynaptic bonding attractors V(Mg,Mg) and V(Ca,Ca). The basin population of the Ca–Ca bond (1.84–1.89e) is about 0.1e smaller than population of the Mg–Mg bond (1.95–1.98e). The results of ELF-analysis support classical Lewis representation of the 2c–2e bonds (single bond). The topological analysis of electron density field, ρ(r) shows that both the Mg–Mg and Ca–Ca bonds are characterised by the non-nuclear attractor (NNA) and pseudo-basin localised in midpoint of the bond. However, in the case of the Ca–Ca bond its localisation depends on the used functional. The median ELF-basin population of the Mg–Mg bond (1.96e) is about 2.5 larger than the population (0.79e) of pseudo-atomic basin associated with NNA of the ρ(r) field. The analysis performed for the nitrogen – magnesium and nitrogen–calcium bonds showed the dative bonds N→Mg and N→Ca with very large values of the polarity index, pNMg, pNCa, 0.96 and median ELF-basin population 3.40e.

Silane activation by laser-ablated Be atoms: Formation of HBeSiH3 and HBe(μ-H)3Si molecules

Laser-ablated beryllium atoms have been reacted with silane molecules during condensation in excess neon and argon at 4K. Absorptions due to HBeSiH3 and HBe(μ-H)3Si were observed and identified on the basis of isotopic IR spectroscopy, deuterium substitution with SiD4, and quantum chemical frequency calculations. The observed results show excited Be atom (1P1:2s12p1) can insert into SiH bond spontaneously and the insertion product rearranges to HBe(μ-H)3Si upon photolysis. The electron localization function (ELF) analysis suggests that 3c-2e hydrogen bridge bond (BeHSi) was formed by the donation of electrons for SiH σ bond to the empty p orbital of Be atom for HBe(μ-H)3Si molecule, which shows much difference from CH bond complexes.