Spin Multiplicity Research Articles

Aromaticity of Bare Iridium Trimers and Ir3M0/+ and $$\rm{Ir}_3M_2^{+/3+}$$ I r 3 M 2 + / 3 + (M = Li, Na, K, and Be, Ca) Bimetallic Clusters

The structural stabilities, bonding nature, electronic properties, and aromaticity of bare iridium trimers $$\rm{Ir}_3^{+/-}$$ with different geometries and spin multiplicities are studied at the DFT/B3LYP level of theory. The ground state of the $$\rm{Ir}_3^{+}$$ cation is found to be the 3A2 (C2v) triplet state and the ground state of the $$\rm{Ir}_3^{-}$$ anion the 5A2 (C2v) quintet state. A detailed molecular orbital (MO) analysis indicates that the ground-state $$\rm{Ir}_3^{+}$$ ion (C2v, 3A2) possesses double (σ and partial δ) aromaticity as well as the ground-state $$\rm{Ir}_3^{-}$$ ion (C2v, 5A2). The multiple d-orbital aromaticity is responsible for the totally delocalized three-center metal-metal bond of the triangular Ir3 framework. $$\rm{Ir}_3^{-}$$ (C2v, 1A1) structure motif is perfectly preserved in pyramidal Ir3M0/+ (Cs, 1A′) and bipyramidal $$\rm{Ir}_3M_2^{+/3+}$$ (C2v, 1A1) (M = Li, Na, K and Be, Ca) bimetallic clusters which also possess the corresponding d-orbital aromatic characters.

Matrix isolation study of the reaction of O (3P) with 1,3 butadiene: Unexpected formation of ethylketene

The light-induced reaction of ozone with 1,3-butadiene in argon matrixes is described, using either red (625 nm) or UV (254 nm) irradiation. Products were observed using infrared spectroscopy and identification was aided by 18O and deuterium experiments. The experimental work was supported by extensive DFT calculations. Four products were anticipated to be formed, ethenyloxirane, 2-butenal, 3-butenal and 2,5-dihydrofuran, and all four were observed. These results suggested the intermediacy of a triplet biradical H2CCHCHCH2O formed through the initial step of the reaction of O 3P with butadiene. In addition, one unexpected product was conclusively identified, ethylketene, formed through a double hydrogen shift after formation of the initial triplet biradical. Some product variation was observed with the different wavelengths of irradiation, reflecting the spin multiplicity of the initially formed O atom.

Many-Body Expanded Full Configuration Interaction. I. Weakly Correlated Regime.

Over the course of the past few decades, the field of computational chemistry has managed to manifest itself as a key complement to more traditional lab-oriented chemistry. This is particularly true in the wake of the recent renaissance of full configuration interaction (FCI)-level methodologies, albeit only if these can prove themselves sufficiently robust and versatile to be routinely applied to a variety of chemical problems of interest. In the present series of works, performance and feature enhancements of one such avenue toward FCI-level results for medium to large one-electron basis sets, the recently introduced many-body expanded full configuration interaction (MBE-FCI) formalism [ J. Phys. Chem. Lett. 2017 , 8 , 4633 ], will be presented. Specifically, in this opening part of the series, the capabilities of the MBE-FCI method in producing near-exact ground state energies for weakly correlated molecules of any spin multiplicity will be demonstrated.

Analysis of time-resolved EPR spectra observed in the photolysis of disulphonated anthraquinones included in cyclodextrins – evidence of the S-T_ mixing of radical pair mechanism

ABSTRACTCyclodextrins (CDs) are well known hosts of inclusion compounds, and they can be used for molecular identification and separation. Several studies have already been reported from the point of view of photchemistry and spin-chemistry. These reports showed that the inside environment of CDs such as their bore-size works for their specific properties. In this report, the time-resolved EPR spectra observed in the photolysis of aqueous solution of disulphonated anthraquinones included in β-CD and γ-CD are carefully analysed. The spectral simulation employing Radical Pair Mechanism (RPM) of Chemically Induced Dynamic Electron Polarisation is carried out. Finally, it is concluded that the peculiar hyperfine-dependence observed in these particular systems is exclusively caused by the mixing RPM, despite the radical pairs (RPs) having small hyperfine coupling (HFC) constants (less than 3.4 mT). Another finding is the quenching of the spin polarisation of the RP conveyed from the excited triplet state of anthraquinones before mixing. This is explained as arising from slow relative diffusional motion of the RP members when included in the interior of the CDs. General expression of the and S-T+ mixing of multiple nuclei (I = 1/2) with different conditions such as the spin multiplicity of the precursor molecule and the sign of the HFC constants, is also suggested.

Charge Compensation Mechanism in Li-Excess Oxides Revealed By Operando Soft/Hard X-Ray Absorption Spectroscopy

Introduction Li-excess metal oxide having high charge-discharge capacity has been expected to realize higher energy density in lithium-ion batteries. Several lithium-excess metal oxides have been studied extensively in order to use effectively the charge compensation by redox reaction of oxide ions. [1-5] In 4d and 5d metal oxides such as Li2RuO3 [1] and Li2IrO3-based systems [2] , high covalent bond between 4d orbital of transition-metal and 2p orbital of oxygen enables charge compensation by the oxidation of oxide ions to peroxo-like dimer. On the other hand, in a 3d transition-metal oxide, Li1.2Ni0.13Co0.13Mn0.54O2 exhibits formation of isolated holes on oxide ions because highly ionized 3d transition-metal ions stabilize the isolated holes on the oxide ions surrounded by lithium ions. [3, 4] Other 3d transition-metal oxides such as Li1.2Ti0.4Mn0.4O2, also exhibit stable oxide ions redox. [5] According to the previous studies, covalent character or ionic character between transition-metal ions and oxide ions in Li-excess metal oxides is a key factor to stabilize oxide ions redox. However, behavior of oxide ions redox in Li-excess metal oxides with different covalent character or ionic character has not been systematically examined. In this study, we focus on four different Li-excess metal oxides, Li2MeO3 (Me = Mn and Ru) and Li1.2Ti0.4Me0.4O2 (Me = Mn and Fe), as models with different covalent character or ionic character. Developing a new operando soft X-ray absorption spectroscopy, we observed directly the electronic state of the oxide ions in these materials during charge process via the technique. [6] Experimental operando soft X-ray absorption spectroscopy measurements were performed at BL27SU in SPring-8, Japan. The absorption spectra were collected with partial fluorescence mode using home-made cell. Composite electrodes were pasted on aluminum sputtered-Si3N4 window. For Li1.2Ti0.4Mn0.4O2, half charged-LiFePO4 was used as a counter electrode, and 4.2 mol dm-3 lithium bis(trifluoromethanesulfonyl)amide/ acetonitrile was used as an electrolyte solution. Two electrode cells were assembled in the Ar-filled grovebox. XAS spectra were collected during galvanostatic measurement at rate of 1/20 C rate at 55°C. Results and Discussion The charge and discharge profiles of the Li1.2Ti0.4Mn0.4O2 showed that the voltage gradually increased at initial stage under charging process, then a plateau was observed at approximately 4.2 V. The first discharge profile was similar to the first charge one. The first discharge capacity was 270 mAh/g, which was comparable to the first charge capacity of 300 mAh/g. operando Mn L-edge XAS spectra of the Li1.2Ti0.4Mn0.4O2 showed that a board peak was observed at 642 eV before charge process. The peak separated to two peaks and shifted higher energy in the slope region of charge process, and the two peaks unchanged with subsequent charge process. The peak separation and shift toward higher energy in the slope region were caused by spin multiplicity and crystal field effect with oxidation Mn ions. No change of the spectra in the subsequently charge process means that the Mn ions did not contribute to the charge compensation. operando O K-edge XAS spectra of Li1.2Ti0.4Mn0.4O2 showed a board peak was observed around 531 eV before charge process. The peak was divided into two peaks during charge process. These peaks reflect transition from O 1s orbitals to hybridized states between 3d orbital of transition-metal and 2p orbital of oxygen. The integrated intensity of the peak at the lower energy increased in the slope region of charge process, whereas the integrated intensity of the peak at the higher energy increased with subsequent charge process. The change of the spectrum in the slope region was caused by oxidation Mn ions (Mn3+ to Mn4+) as observed in the Mn-L XANES spectra. The increase of the integrated intensity at the higher energy in the subsequently charge process was caused by oxidization of oxygen ions.

Physics and chemistry of graphene. Emergentness, magnetism, mechanophysics and mechanochemistry

Graphene is considered a specific object whose electronic structural features are presented in the light of the general concept of emergent phenomena that arise as a result of a quantum phase transition caused by the breaking of continuous symmetry. This review starts by examining the spin symmetry breaking of the graphene electron subsystem caused by the correlation of its odd pz-electrons that depends on the distance between these electrons and becomes noticeable when the shortest distance, determined by the C = C bond length, exceeds the critical magnitude Rcr = 1.395 Å. The symmetry breaking is reliably predicted by the unrestricted Hartree–Fock (UHF) formalism, which provides a sufficient level of quantitative self-consistent description for the problem. Empirical support has been given to and reliable certification obtained for UHF emergents such as (i) open-shell electron spin-orbitals; (ii) splitting and/or spin polarization of electron spectra; (iii) a spin-mixed ground state and, as a consequence, violation of the exact spin multiplicity of electronic states, and (iv) the existence of local spins at zero total spin density. Using this approach greatly expands our understanding of the ground state of graphene and other sp2 nanocarbons and not only gives a clear insight into the spin features of graphene chemistry, accentuating its emergent character, but also expectedly predicts the occurrence of new graphene physics-related emergents. In the latter case, symmetry breaking is relevant for both the spin system and time reversal and imposes on graphene special physical properties such as ferromagnetism, superconductivity, and topological nontriviality. This review shows, for the first time, that not only the ferromagnetism but also the mechanical properties of graphene are essentially emergent, extending this feature to the entire physics of graphene.

Low-Spin Fe(III) Macrocyclic Complexes of Imidazole-Appended 1,4,7-Triazacyclononane as Paramagnetic Probes.

Two macrocyclic complexes of 1,4,7-triazacyclononane (TACN), one with N-methyl imidazole pendants, [Fe(Mim)]3+, and one with unsubstituted NH imidazole pendants, [Fe(Tim)]3+, were prepared with a view toward biomedical imaging applications. These low-spin Fe3+ complexes produce moderately paramagnetically shifted and relatively sharp 1H NMR resonances for paraSHIFT and paraCEST applications. The [Fe(Tim)]3+ complex undergoes pH-dependent changes in NMR spectra in solution that are consistent with the consecutive deprotonation of all three imidazole pendant groups at high pH values. N-Methylation of the imidazole pendants in [Fe(Mim)]3+ produces a complex that dissociates more readily at high pH in comparison to [Fe(Tim)]3+, which contains ionizable donor groups. Cyclic voltammetry studies show that the redox potential of [Fe(Mim)]3+ is invariant with pH ( E1/2 = 328 ± 3 mV vs NHE) between pH 3.2 and 8.4, unlike the Fe(III) complex of Tim which shows a 590 mV change in redox potential over the pH range of 3.3-12.8. Magnetic susceptibility studies in solution give magnetic moments of 0.91-1.3 cm3 K mol-1 (μeff value = 2.7-3.2) for both complexes. Solid-state measurements show that the susceptibility is consistent with a S = 1/2 state over the temperature range of 0 to 300 K, with no crossover to a high-spin state under these conditions. The crystal structure of [Fe(Mim)](OTf)3 shows a six-coordinate all-nitrogen bound Fe(III) in a distorted octahedral environment. Relativistic ab initio wave function and density functional theory (DFT) calculations on [Fe(Mim)]3+, some with spin orbit coupling, were used to predict the ground spin state. Relative energies of the doublet, quartet, and sextet spin states were consistent with the doublet S = 1/2 state being the lowest in energy and suggested that excited states with higher spin multiplicities are not thermally accessible. Calculations were consistent with the magnetic susceptibility determined in the solid state.

Reactivity of CO on Ni4 cluster- effect of spin multiplicity and H doping-A DFT investigation

We investigated the reactivity of carbon monoxide on tetrahedral Ni4 clusters at different spin multiplicity applying density functional theory calculations considering pure and hybrid functional. The stability of the clusters increases with the increasing spin multiplicity and doping hydrogen in Ni4 cluster. The adsorption or binding energy of CO on Ni4 cluster is thermodynamically feasible process at normal condition whereas dissociation is not feasible. Ab initio molecular orbital analysis shows the orbital overlaps are observed at bridging site, three fold sites, and tetra coordinated centre and formation of δ-bond in the cluster. In NBO analysis, CO binds strongly to the Ni4 cluster not only by two NiC bond (spd hybrid), but also donor-acceptor delocalization interactions, for example, σ type BD(CO) → BD*(NiC) and BD(NiC) → BD*(NiC/CO), two π-type BD(CO) → LP*(Ni) and several diffuse RY*(C) ← LP(Ni) and π*(CO) ← LP(Ni) interactions. Singlet Ni4 cluster shows highest activation energy barrier, 3 eV. H-doped Ni4 cluster decreases dissociation barrier and favors CH bond formation.

Thickness-Dependent Reactivity of O2 on Cu Layers Grown on Ru(0001) Surfaces

The reaction of diatomic molecules on bimetallic surfaces, formed by one to few monolayers of a metal adsorbed on a different metal substrate, is relevant to understand the role of surface strain and substrate chemical binding in catalysis, which is interesting for industrial applications, challenges existing state-of-the-art theoretical methods, due to the additional complexity associated with having a molecule with triplet spin multiplicity. Here, we have studied the interaction of O2 with CuxML/Ru(0001) (x being the number of Cu monolayers), for which experimental data are available, by means of multidimensional classical dynamics simulations based on first-principles potential energy surfaces. Our results show, on the one hand, that the inclusion of the surface temperature on the simulations is essential to reproduce the experimental observations, and therefore, to analyze the physical mechanisms behind these observations, and, on the other hand, that electronic effects due to the binding between the ...

Dependence of Properties and Exchange Coupling Constants on the Charge in the Mn2O n and Fe2O n Series.

The geometrical structure and properties of the neutral and singly charged Mn2O nq and Fe2O nq clusters ( q = 0, ±1) are computed using density functional theory with the generalized gradient approximation in the range 1 ≤ n ≤ 7. The geometrical structures and spin multiplicities of the corresponding species in all six series are similar except for a few exceptions. Antiferromagnetic coupling of total spin magnetic moments of the metal atoms in the lowest total energy states is observed for the majority of species in all six series when n = 1-5; correspondingly, the computed magnetic exchange coupling constants are mostly negative. The states of Mn2O nq and Fe2O nq are nonmagnetic or weakly ferromagnetic when n > 5 except for Mn2O7+ where the ground state is antiferromagnetic. The computed adiabatic electron affinities and ionization energies of the neutral species in both series are quite close to one another and increase as n increases. However, the binding energies of a single oxygen atom and of an O2 dimer decrease as n increases and the Mn2O7+ and Fe2O7+ cations are barely stable with respect to the O2 abstraction. The most stable and least stable species at a given n are the anions and the cations, respectively. The electric dipole polarizability per atom decreases sharply when n moves from 1 to 4 and then remains nearly constant for larger n values in the anion series, whereas it is close to the asymptotic value already at n = 2 in the neutral series.

Comparative investigation of the emission characteristics between 6.78-MHz radio-frequency and direct-current glow discharge plasmas for atomic emission spectrometry

This paper focused on the characteristics of emission spectra excited by a Grimm-style glow discharge plasma source in a 6.78-MHz radio-frequency (RF) power mode, in comparison to a conventional direct-current (DC) power mode. For this purpose, Boltzmann plots for atomic emission lines of iron were analyzed in detail, when the RF forward power and argon pressure in the discharge chamber were selected as the experimental parameters. The Boltzmann plot for low-lying excited levels of iron atom (3.4–4.8 eV) was on a linear relationship to provide an excitation temperature, whereas emission lines having larger excitation energies (more than 5 eV) generally deviated upwards from the linear relation. Any systematic dependence on the spin multiplicity was not found among the high-lying excited levels in the Boltzmann plot. The reason for the phenomenon was considered as follows: (1) the excitation for the low-lying emission lines would be caused by a dominant thermal collision process and (2) any non-thermal process also contributed to excitations for the high-lying emission lines to cause their over-population as a whole. The resultant excitation temperature was obtained in a narrow range of 3400–3600 K, which was hardly affected by the discharge power and the argon pressure, and further, the excitation temperature was very similar to that of a DC plasma that we had already reported. This result suggested that the glow discharge plasma could be supported by a self-stabilized negative glow region, where the kinetic energy distribution of the particles would be changed to a lesser extent as far as a stable discharge could be maintained.

Structural and electronic properties of SbnAl(0,±1) (n = 1–10) clusters using density-functional theory

We used the density functional theory (DFT) with the unrestricted B3LYP exchange-correlation potential and LanL2DZ basis sets to optimize the geometries of SbnAl and SbnAl±1 (n = 1–10) clusters. We mainly utilized Gaussian 03 W software to calculate the data. In order to find the most stable structure of each isomer, we calculated the total energy, the spin multiplicity (S), point group symmetry (PG), the electronic state (State), and the average bond lengths of Sb-Al bond and Sb-Sb bond (R1 and R2). Through the calculations and analysis of these data, we found the ground state structure of each group isomer. By discussing the average binding energy (Eb), fragmentation energy (Ef), and the second-order energy difference (Δ2E), the stabilities of the SbnAl (0,±1) clusters were studied. The results of the electron transfer show that the Sb4Al and Sb8Al clusters are different with the other neutral clusters. In order to study the electric properties of SbnAl (0,±1) clusters, the energy gap (Eg) between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), AEA, VDE, AIP, and VIP were calculated. Besides, the magnetic moment of the positive and negative clusters have the same effects when n = 2–9.

A Quantum Chemical Study of C60Cl30, C60(OH)30 Molecules and Fe@C60(OH)30 Endocomplex

(U)PBE0/cc-pVDZ method is used to study the structure of C60Cl30, C60(OH)30 molecules and Fe@C60(OH)30 endocomplex. The triplet state of the endocomplex is shown to be the lowest in energy among its four states corresponding to different spin multiplicities and positions of Fe nucleus within the fullerene cavity. This state is characterized by bonding between the iron atom and one of two benzenoid cycles of the carbon cage, six internuclear Fe–C distances (208 pm), and 1s22s22p63s23p63d7.24s0.14p0.3 electron configuration of iron with spin population of 2.36.

Synthesis of an Iron(IV) Aqua-Oxido Complex Using Ozone as an Oxidant.

The iron(IV) oxido complex [(tmc)Fe=O(OTf)]OTf with the macrocyclic ligand 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclo-tetradecane (tmc) has been synthesized using ozone as an oxidant. By adding water to this compound the complex [(H2 O)(tmc)Fe=O)](OTf)2 could be prepared. This complex is important in regard to a better understanding of the reactivity of FeIV oxido complexes. Mössbauer measurements using the solid compound showed an isomer shift of δ=0.19 mm s-1 and a quadrupole splitting ΔEQ =1.38 mm s-1 , confirming the high-valent FeIV state. DFT calculations were performed and led to an assignment of triplet spin multiplicity. Crystallographic characterization of [(H2 O)(tmc)Fe=O)](OTf)2 as well as of starting materials [(tmc)Fe(CH3 CN)](OTf)2 and [(tmc)Fe(OTf)]OTf together with previous results strongly suggest that [(H2 O)(tmc)Fe=O)](OTf)2 was formed similar to the oxido-hydroxido tautomerism analogous to heme systems.

Synthesis of an Iron(IV) Aqua–Oxido Complex Using Ozone as an Oxidant

AbstractThe iron(IV) oxido complex [(tmc)Fe=O(OTf)]OTf with the macrocyclic ligand 1,4,8,11‐tetramethyl‐1,4,8,11‐tetraazacyclo‐tetradecane (tmc) has been synthesized using ozone as an oxidant. By adding water to this compound the complex [(H2O)(tmc)Fe=O)](OTf)2 could be prepared. This complex is important in regard to a better understanding of the reactivity of FeIV oxido complexes. Mössbauer measurements using the solid compound showed an isomer shift of δ=0.19 mm s−1 and a quadrupole splitting ΔEQ=1.38 mm s−1, confirming the high‐valent FeIV state. DFT calculations were performed and led to an assignment of triplet spin multiplicity. Crystallographic characterization of [(H2O)(tmc)Fe=O)](OTf)2 as well as of starting materials [(tmc)Fe(CH3CN)](OTf)2 and [(tmc)Fe(OTf)]OTf together with previous results strongly suggest that [(H2O)(tmc)Fe=O)](OTf)2 was formed similar to the oxido–hydroxido tautomerism analogous to heme systems.

Exploiting Charge-Transfer States for Maximizing Intersystem Crossing Yields in Organic Photoredox Catalysts.

A key feature of prominent transition-metal-containing photoredox catalysts (PCs) is high quantum yield access to long-lived excited states characterized by a change in spin multiplicity. For organic PCs, challenges emerge for promoting excited-state intersystem crossing (ISC), particularly when potent excited-state reductants are desired. Herein, we report a design exploiting orthogonal π-systems and an intermediate-energy charge-transfer excited state to maximize ISC yields (ΦISC) in a highly reducing ( E0* = -1.7 V vs SCE), visible-light-absorbing phenoxazine-based PC. Simple substitution of N-phenyl for N-naphthyl is shown to dramatically increase ΦISC from 0.11 to 0.91 without altering catalytically important properties, such as E0*.

Predicting Intersystem Crossing Rates with AIMS-DFT Molecular Dynamics.

Accurate prediction of the intersystem crossing rates is important for many different applications in chemistry, physics, and biology. Recently, we implemented the ab initio multiple spawning (AIMS) molecular dynamics method to describe the intersystem crossing processes, where nonradiative transitions between electronic states with different spin multiplicities are mediated by spin-orbit coupling. Our original implementation of the direct AIMS dynamics used the complete active space self-consistent field (CASSCF) method to describe multiple coupled electronic states on which multidimensional Gaussian wave packets were propagated. In this work, we improve the computational efficiency and versatility of the AIMS dynamics by interfacing it with the density functional theory (DFT). The new AIMS-DFT and the earlier AIMS-CASSCF implementations are used to investigate the effects of electronic structure methods on the predicted intersystem crossing rate constants and the lowest triplet state lifetime in the GeH2 molecule. We also compare the rates and lifetimes obtained from the AIMS simulations with those predicted by the statistical nonadiabatic transition state theory (NA-TST). In NA-TST, the probabilities of spin transitions are calculated using the Landau-Zener, weak coupling, and Zhu-Nakamura formulas. Convergence of the AIMS rate constants with respect to the simulation time and the number of initial trajectories (Gaussian wave packets) is analyzed. An excellent agreement between AIMS-DFT and AIMS-CASSCF can be explained by cancelation of two effects: higher energy barriers and a stronger spin-orbit coupling in DFT relative to CASSCF. The rate constants obtained with the AIMS-DFT dynamics are about a factor of 2 larger than those predicted by the statistical NA-TST. This is likely due to the importance of the nonlocal interstate transitions missing from the NA-TST description.

A comment on “The interaction of [formula omitted] (X = F, Cl, and Br) with active sites of graphite” [Xu et al., Chem. Phys. Lett., 418, 413 (2006)

In their article, Xu et al. (2006) present the adsorption energies for the chemisorption of the three halogens F2, Cl2, and Br2 on the active sites of graphite. The three investigated systems are the three most stable surfaces, (001), (100), and (110); the latter two are also called zigzag and armchair surface, respectively. Due to some inconsistencies in their article, we re-evaluated the results of Xu et al. in order to investigate the impact on the adsorption energies of the halogens. For the (001) surface, our results agree with Xu et al. However, for the other two surfaces we find major differences. Contrary to Xu et al., we find that the halogens adsorb the strongest on the zigzag surface. The second strongest adsorption is found on the armchair surface for the symmetric configurations, the third strongest for the asymmetric configurations. Several reasons are given which explain this discrepancy. The most striking source of error in the work of Xu et al. is due to the fact that they did not choose the correct spin multiplicities for the model systems which means that they performed the calculations in excited states. This leads to errors between 50 and 600% for the zigzag surface and 3–42% for the armchair surface.

Adsorption and possible dissociation of glucose by the [BN fullerene-B6]− magnetic nanocomposite. In silico studies

The adsorption, activation and possible dissociation of the glucose molecule on the magnetic [BN fullerene-B6]− system is performed by means of density functional theory calculations. Three models of magnetic nanocomposites were inspected: i) pristine BN fullerene, BN fullerene functionalized with a magnetic B6 cluster which generates two structures: ii) pyramidal (P) and iii) triangular (T). Chemical interactions of glucose appear for all these cases; however, for the BNF:B6(T)—glucose system, the interaction generates an effect of dissociation on glucose, due to the magnetic effects, since it has high spin multiplicity. The latter nanocomposite shows electronic behavior like-conductor and like-semi-conductor for the P and T geometries, respectively. Intrinsic magnetism associated to values of 1.0 magneton bohr (µB) for the pyramidal and 5.0 µB for the triangular structure, high polarity, and low-chemical reactivity are found for these systems. These interesting properties make these functionalized fullerenes a good option for being used as nano-vehicles for drug delivery. These quantum descriptors remain invariant when the [BN]−fullerene and [BNF:B6 (P) or (T)]− nanocomposites are interacting with the glucose molecule. According to the determined adsorption energy, chemisorption regimes occur in both the phases: gas and aqueous medium.

A Definition of the Magnetic Transition Temperature Using Valence Bond Theory.

Macroscopic magnetic properties are analyzed using Valence Bond theory. Commonly the critical temperature TC for magnetic systems is associated with a maximum in the energy-based heat capacity Cp(T). Here a more broadly applicable definition of the magnetic transition temperature TC is described using the spin moment expectation value (i.e., applying the spin exchange density operator) instead of energy. Namely, the magnetic capacity Cs(T) reflects variation in the spin multiplicity as a function of temperature, which is shown to be related to ∂[χT(T)]/∂T. Magnetic capacity Cs(T) depends on long-range spin interactions that are not relevant in the energy-based heat capacity Cp(T). Differences between Cs(T) and Cp(T) are shown to be due to spin order/disorder within the crystal that can be monitored via a Valence Bond analysis of the corresponding magnetic wave function. Indeed the concept of the Boltzmann spin-alignment order is used to provide information about the spin correlation between magnetic units. As a final illustration, the critical temperature is derived from the magnetic capacity for several molecular magnets presenting different magnetic topologies that have been experimentally studied. A systematic shift between the transition temperatures associated with Cs(T) and Cp(T) is observed. It is demonstrated that this shift can be attributed to the loss of long-range spin correlation. This suggests that the magnetic capacity Cs(T) can be used as a predictive tool for the magnetic topology and thus for the synthetic chemists.