Добірка наукової літератури з теми "EDA-NOCV"

Fluorescent diarylchlorostibane, distibane are utilized as precursors for syntheses of redox-active dimeric/trimeric alkali-metal antimonides by reductive dehalogenation. DFT and EDA-NOCV analysis are performed to shed light on the electron transfer mechanism.

The chemical bonds in donor–acceptor stabilized linear and cyclic (BN)_n (n = 1–3) adducts are examined using natural bond orbital (NBO), atoms-in-molecules (AIM), and energy decomposition (EDA-NOCV) analyses.

The bonding and stability of elusive heavier cyanogen halide analogues (L′)PSi(X)(L) have been theoretically investigated using EDA-NOCV method. Variation of ligands and halogen on Si atom had a significant effect on the stability of these species.

Comparison of the results of EDA-NOCV for the M←C bond in [NHC(R) → MR′] and [{P(Ph)₃CHR} ← MCl] complexes reveals that the phosphorus ylides are slightly better σ-donors and weaker π-acceptors than the corresponding NHC(R).

Reactions of laser-ablated B and Al atoms with BF3 have been explored in the 4 K excess neon through the matrix isolation infrared spectrum, isotopic substitutions and quantum chemical calculations. The inserted complexes F2BMF (M = B, Al) were identified by anti-symmetric and symmetric stretching modes of F-B-F, and the F-11B-F stretch modes are at 1336.9 and 1202.4 cm−1 for F211B11BF and at 1281.5 and 1180.8 cm−1 for F211BAlF. The CASSCF analysis, EDA-NOCV calculation and the theory of atoms-in-molecules (AIM) are applied to investigate the bonding characters of F2BBF and F2BAlF molecules. The bonding difference between boron and aluminum complexes reveals interesting chemistries, and the FB species stabilization by a main group atom was first observed in this article.

The mechanism of the carbonylation of diazomethane in the presence of iron–carbonyl–phosphine catalysts has been investigated by means of DFT calculations at the M06/def-TZVP//B97D3/def2-TZVP level of theory, in combination with the SMD solvation method. The reaction rate is determined by the formation of the coordinatively unsaturated doublet-state Fe(CO)3(P) precursor followed by the diazoalkane coordination and the N2 extrusion. The free energy of activation is predicted to be 18.5 and 28.2 kcal/mol for the PF3 and PPh3 containing systems, respectively. Thus, in the presence of less basic P-donor ligands with stronger π-acceptor properties, a significant increase in the reaction rate can be expected. According to energy decomposition analysis combined with natural orbitals of chemical valence (EDA–NOCV) calculations, diazomethane in the Fe(CO)3(phosphine)(η1-CH2N2) adduct reveals a π-donor–π-acceptor type of coordination.

Quantum chemical calculations using density functional theory at the BP86 level in conjunction with triple-zeta polarized basis sets have been carried out for the title compounds. The nature of the bonding between the diatomic fragment and the NHC ligands is investigated with an energy decomposition analysis. The chemical bonds in the [(NHCMe)2(E2)] complexes can be discussed in terms of donor-acceptor interactions which consist of two NHCMe→E2←NHCMe donor components and two weaker components of the NHCMe←E2→NHCMe π backdonation. The out-of-phase (+)=(-) contribution of the s donation is always stronger than the in-phase (+)=(+) contribution. The electronic reference state of N2 in the dinitrogen complex [(NHCMe)2(N2)] is the highly excited 11Γg state which explains the anti-periplanar arrangement of the ligands. The gauche arrangement of the ligands in the heavier homologues [(NHCMe)2(E2)] (E = P-Bi) may be discussed using either the excited 11Γg state or the X1Σg+ ground state of E2 as reference states for the donor-acceptor bonds. The EDA-NOCV calculations suggest that the latter bonding model is better suited for the complexes where E = As-Bi while the phosphorus complex is a borderline case.

Spin crossover (SCO) active metal complexes are highly versatile materials thanks to their sensitivity to tiny physical or chemical environmental changes. This property makes them very useful for a wide range of applications: employable for experimental studies as molecular switches or for theoretical studies investigating the M-L bonds. In both cases, these studies aim to develop strategies of predictably tuning them. Chapter One. An introduction to the SCO phenomenon: from gradual to cooperative SCO; various methods of monitoring the SCO transition. A summary of some literature examples of SCO-active systems is given. An overview of the published achievements in predicting the SCO phenomenon, including an introduction to the computational models deployed across the years. The EDA-NOCV model, employed in this field for the first time in this PhD thesis, is introduced. Finally, the aims of this study are presented. Chapter Two. The synthesis and characterisation of four new non-symmetrical ligands, 3-(2-(5-Z-pyridyl))-4-tolyl-5-phenyl-1,2,4-triazole (LpytZ, Z = CF3, Br, F, Me), and the corresponding [FeII(LpytZ)2(NCBH3)2] complexes are presented. All four of these new complexes are SCO-active in the solid state and in CDCl3 solution, but T1/2 tuning by the meta-Z substituents was very modest. Three literature families were also tested, successfully extending the generality of using the 15N NMR chemical shift δNA of the coordinated nitrogen atom of the free ligand as measure of the T1/2 in the resulting Fe(II) complex. Chapter Three. Theoretical study of a family of five iron(II) SCO-active [Fe(Lazine)2(NCBH3)2] (Lazine = 3-(2-azinyl)-4-tolyl-5-phenyl-1,2,4-triazole) and of the related five LS [Fe(Lazine)3(BF4)2]. The EDA-NOCV model was applied to molecular fragments to provide quantitative assessment of the σ- and π-bonding. A new corrected [Mn+ + L6] fragmentation was implemented which promises to enable a general approach suitable for any ML6 system. Finally, the σ- and π-bonding character is strongly correlated with the experimental T1/2 of the SCO-active [Fe(Lazine)2(NCBH3)2] complexes. Chapter Four. Theoretical study of the M-L bond in a family of sixteen SCO-active differently para-X substituted [Fe(bppX)2]2+ complexes (bppX is 2,6-di(pyrazol-1-yl)-4-X-pyridine). Results of the EDA-NOCV revealed the σ-strength of the bppX ligand is correlated with σp+(X), δNA(bppX), experimental T1/2([Fe(bppX)2]2+) and calculated AILFT ΔO([Fe(bppX)2]2+). Results are explained at the molecular level by investigating the orbital population of the valence orbitals of the coordinating nitrogen involved in the aromatic π-system (pπ) and in the Fe-N bond (sp2(Fe)). From the observed correlations, the unknown σp+ parameter for two substituents (X = SOMe, SO2Me) is predicted. Chapter Five. First theoretical study on [CoII(dpzca)2] SCO in the solid state, aiming to establish a computational protocol able to predict experimental T1/2 in pressure-activated SCO. The first part of the study validated a DFT protocol at p = 1 bar. The protocol was then extended and trialled up to 4300 bar. Results revealed good reproduction of the experimental results up to 2100 bar; but beyond this pressure, the theoretical and experimental findings diverge. Theoretical data suggest a possible phase change for the crystalline structure of HS [CoII(dpzca)2] at higher pressures than 2100 bar; this would explain why the implemented computational protocol lost validity.