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The low-spin–high-spin energy splitting of states of different multiplicity for the trans - ͓ Fe Ј ͑ N H S 4 ͒ Ј PH 3 ͔ complex. DFT calculations were per-
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The exact exchange part in hybrid density functionals is analyzed with respect to the prediction of ground state multiplicities. It has been found [M. Reiher, O. Salomon, and B. A. Hess, Theor. Chem. Acc., 107, 48 (2001)] that pure and hybrid density functionals yield energy splittings between high-spin and low-spin states of Fe-sulfur complexes th...
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Context 1
... conformation. The general structure of these compounds is depicted in Fig. 1. The structure of the compounds is satisfactorily repro- duced with the B3LYP and the B3LYP Ã functionals. Table V compares the characteristic bond lengths of the metallocenes with those found experimentally. The deviations are usually less than 4 pm with both functionals, which is small in view of the fact that the calculated structures are always in their staggered conformation while this is not necessarily the case for the experimentally found structures. To examine the influence of the exact exchange on the multiplicity of the ground state of metallocenes the high- spin–low-spin energy splitting is plotted against the exact exchange admixture parameter c 3 in Fig. 2. This figure shows a linearity of the energy difference between states of different multiplicity as a function of the exact exchange admixture for all fourth-period transition metal compounds. While almost all complexes feature a negative slope, chro- mocene exhibits a very small positive slope such that the splitting is almost independent of c 3 . For this complex we found that another singlet structure is close in energy for small c 3 values. For this second close-lying singlet structure we get a large negative slope for the energy splitting. Manganocene and cobaltocene are of special interest, because here the spin state of the ground state changes with variation of the exact exchange. While B3LYP and B3LYP Ã give a low-spin ground state for cobaltocene and a high-spin ground state is favored only for c 3 Ͼ 0.22, the calculation of manganocene finds a low-spin ͑ S ϭ 0.5 ͒ compound for an exact exchange proportion of less than 14.3% and a high-spin ͑ S ϭ 2.5 ͒ compound with an exchange greater than this value. Experimentally manganocene possesses a high-spin ground state as can be seen in Table VI, which lists the experimental and calculated magnetic moments. Furthermore, taking into account that ⌬ E a / b is larger than zero we again arrive at the value of 15% for the optimal representation of the splitting. It is known that manganocene is close to the high-spin–low- spin crossover point: 30 The experimentally found energy difference is about 2 kJ/mol. The B3LYP Ã functional describes manganocene with an energy difference of 4 kJ/mol signifi- cantly better than B3LYP with 33.5 kJ/mol. Manganocene corroborates the 15% value in B3LYP in the sense that it provides a lower bound to c 3 . Therefore, a reduction of the exact exchange from 20% to 15% is highly effective for this type of manganese complexes indicating that B3LYP Ã is of general applicability. Fourth-period bis benzene metal compounds from Ti to Ni were examined in order to study the influence of exact exchange admixture on the high-spin–low-spin splitting for a second class of transition metal compounds with larger struc- tural diversity. Structure optimization for the bis ͑ benzene ͒ metal compounds starting from staggered conformations lead to changes in hapticity and conformation. The optimized minimum structures are shown in Fig. 3. With the exception of bis ͑ benzene ͒ manganese, for which the cationic species was calculated, and two-fold posi- tively charged bis ͑ benzene ͒ nickel only neutral compounds were studied. Bis ͑ benzene ͒ manganese shows a conformational change from the staggered singlet state to a distorted eclipsed conformation in the triplet state. Figure 4 shows that for the energy difference of high- spin and low-spin states a linear dependence on the parameter for exact exchange is found for all bis ͑ benzene ͒ metal compounds considered. Table VII compares the experimentally determined magnetic moments with the spin-only values from B3LYP and B3LYP Ã calculations. No change in the ground state multiplicity is found in the range c 3 ͓ 0.00,0.20 ͔ . Both functionals thus reproduce the experimental magnetic moments well. Our results presented so far show that a functional with reduced exact exchange admixture performs very well with respect to thermochemical quantities and yields transferable results for other metal complexes. In this section we should like to address the following questions: ͑ i ͒ how does the linear relationship established for ⌬ E a / b as a function of c 3 depend on the magnitude of the multiplicity difference, ͑ ii ͒ how does ⌬ E a / b ( c 3 ) behave over the whole range of c 3 ͓ 0.00,1.00 ͔ , and ͑ iii ͒ can we understand that nonlinear terms are small for modest deviations of c 3 from zero? First of all, we should mention that the slope obviously depends on the difference of the spin multiplicities: a singlet state compared to a quintet state yields a larger slope than the singlet compared to a triplet state. In order to demonstrate the different slopes caused by different ⌬ S values we report in Fig. 5 results for the iron–sulfur complexes depicted in Fig. 6. In addition to the discussion in Ref. 9 we now also include triplet states in our study. Figure 5 shows that the slope for the singlet–quintet energy difference is much bigger than for the singlet–triplet case for neutral Fe ͑ II ͒ compounds. This explains why the energetic ordering of states calculated with pure density functionals is ͗ E S ϭ 0 ͘ Ͻ ͗ E S ϭ 1 ͘ Ͻ ͗ E S ϭ 2 ͘ for the compounds under consideration, while we obtain ͗ E S ϭ 2 ͘ Ͻ ͗ E S ϭ 0 ͘ Ͻ ͗ E S ϭ 1 ͘ with hybrid functionals. Note that the effects are less pronounced for the cationic Fe ͑ III ͒ complexes. The energy splitting of manganocene is plotted in Fig. 7 in order to examine the slope of the exact exchange admixture over the whole range of the parameter c 3 . For c 3 ϭ 1.0, the intersections with the ordinate are comparable to the Hartree–Fock values for the splittings: these 100% values differ only little from the Hartree–Fock results ( Ϫ 395.4 kJ/ mol for the doublet–sextet splitting and Ϫ 83.8 kJ/mol for the doublet–quartet splitting ͒ . The small difference is due to the effect of the correlation functional still present in the DFT calculations. For c 3 ϭ 0.0, the intersection with the ordinate compares well with the splittings from BLYP calculations, which are ϩ 62.6 kJ/mol for the doublet–sextet splitting and ϩ 71.7 kJ/mol for the doublet–quartet splitting. All points were generated from optimized structures except for the point at c 3 ϭ 1.0, which was obtained from a single-point energy calculation using the structure optimized for c 3 ϭ 0.8. At this exact exchange admixture of 100%, i.e., close to the Hartree–Fock value of the splitting, a new structure becomes the minimum for the singlet state. The energy splitting deviates surprisingly little from the linear relationship at small values of c 3 up to c 3 Ϸ 0.5. The energy splitting ⌬ E a / b from two different spin states S a and S b , ⌬ E ϭ E Ϫ E , ͑ 2 ...
Context 2
... with a small or almost vanishing slope. Structure optimizations were performed for neutral metallocenes of the fourth period from Ti to Ni in their staggered conformation. The general structure of these compounds is depicted in Fig. 1. The structure of the compounds is satisfactorily repro- duced with the B3LYP and the B3LYP Ã functionals. Table V compares the characteristic bond lengths of the metallocenes with those found experimentally. The deviations are usually less than 4 pm with both functionals, which is small in view of the fact that the calculated structures are always in their staggered conformation while this is not necessarily the case for the experimentally found structures. To examine the influence of the exact exchange on the multiplicity of the ground state of metallocenes the high- spin–low-spin energy splitting is plotted against the exact exchange admixture parameter c 3 in Fig. 2. This figure shows a linearity of the energy difference between states of different multiplicity as a function of the exact exchange admixture for all fourth-period transition metal compounds. While almost all complexes feature a negative slope, chro- mocene exhibits a very small positive slope such that the splitting is almost independent of c 3 . For this complex we found that another singlet structure is close in energy for small c 3 values. For this second close-lying singlet structure we get a large negative slope for the energy splitting. Manganocene and cobaltocene are of special interest, because here the spin state of the ground state changes with variation of the exact exchange. While B3LYP and B3LYP Ã give a low-spin ground state for cobaltocene and a high-spin ground state is favored only for c 3 Ͼ 0.22, the calculation of manganocene finds a low-spin ͑ S ϭ 0.5 ͒ compound for an exact exchange proportion of less than 14.3% and a high-spin ͑ S ϭ 2.5 ͒ compound with an exchange greater than this value. Experimentally manganocene possesses a high-spin ground state as can be seen in Table VI, which lists the experimental and calculated magnetic moments. Furthermore, taking into account that ⌬ E a / b is larger than zero we again arrive at the value of 15% for the optimal representation of the splitting. It is known that manganocene is close to the high-spin–low- spin crossover point: 30 The experimentally found energy difference is about 2 kJ/mol. The B3LYP Ã functional describes manganocene with an energy difference of 4 kJ/mol signifi- cantly better than B3LYP with 33.5 kJ/mol. Manganocene corroborates the 15% value in B3LYP in the sense that it provides a lower bound to c 3 . Therefore, a reduction of the exact exchange from 20% to 15% is highly effective for this type of manganese complexes indicating that B3LYP Ã is of general applicability. Fourth-period bis benzene metal compounds from Ti to Ni were examined in order to study the influence of exact exchange admixture on the high-spin–low-spin splitting for a second class of transition metal compounds with larger struc- tural diversity. Structure optimization for the bis ͑ benzene ͒ metal compounds starting from staggered conformations lead to changes in hapticity and conformation. The optimized minimum structures are shown in Fig. 3. With the exception of bis ͑ benzene ͒ manganese, for which the cationic species was calculated, and two-fold posi- tively charged bis ͑ benzene ͒ nickel only neutral compounds were studied. Bis ͑ benzene ͒ manganese shows a conformational change from the staggered singlet state to a distorted eclipsed conformation in the triplet state. Figure 4 shows that for the energy difference of high- spin and low-spin states a linear dependence on the parameter for exact exchange is found for all bis ͑ benzene ͒ metal compounds considered. Table VII compares the experimentally determined magnetic moments with the spin-only values from B3LYP and B3LYP Ã calculations. No change in the ground state multiplicity is found in the range c 3 ͓ 0.00,0.20 ͔ . Both functionals thus reproduce the experimental magnetic moments well. Our results presented so far show that a functional with reduced exact exchange admixture performs very well with respect to thermochemical quantities and yields transferable results for other metal complexes. In this section we should like to address the following questions: ͑ i ͒ how does the linear relationship established for ⌬ E a / b as a function of c 3 depend on the magnitude of the multiplicity difference, ͑ ii ͒ how does ⌬ E a / b ( c 3 ) behave over the whole range of c 3 ͓ 0.00,1.00 ͔ , and ͑ iii ͒ can we understand that nonlinear terms are small for modest deviations of c 3 from zero? First of all, we should mention that the slope obviously depends on the difference of the spin multiplicities: a singlet state compared to a quintet state yields a larger slope than the singlet compared to a triplet state. In order to demonstrate the different slopes caused by different ⌬ S values we report in Fig. 5 results for the iron–sulfur complexes depicted in Fig. 6. In addition to the discussion in Ref. 9 we now also include triplet states in our study. Figure 5 shows that the slope for the singlet–quintet energy difference is much bigger than for the singlet–triplet case for neutral Fe ͑ II ͒ compounds. This explains why the energetic ordering of states calculated with pure density functionals is ͗ E S ϭ 0 ͘ Ͻ ͗ E S ϭ 1 ͘ Ͻ ͗ E S ϭ 2 ͘ for the compounds under consideration, while we obtain ͗ E S ϭ 2 ͘ Ͻ ͗ E S ϭ 0 ͘ Ͻ ͗ E S ϭ 1 ͘ with hybrid functionals. Note that the effects are less pronounced for the cationic Fe ͑ III ͒ complexes. The energy splitting of manganocene is plotted in Fig. 7 in order to examine the slope of the exact exchange admixture over the whole range of the parameter c 3 . For c 3 ϭ 1.0, the intersections with the ordinate are comparable to the Hartree–Fock values for the splittings: these 100% values differ only little from the Hartree–Fock results ( Ϫ 395.4 kJ/ mol for the doublet–sextet splitting and Ϫ 83.8 kJ/mol for the doublet–quartet splitting ͒ . The small difference is due to the effect of the correlation functional still present in the DFT calculations. For c 3 ϭ 0.0, the intersection with the ordinate compares well with the splittings from BLYP calculations, which are ϩ 62.6 kJ/mol for the doublet–sextet splitting and ϩ 71.7 kJ/mol for the doublet–quartet splitting. All points were generated from optimized structures except for the point at c 3 ϭ 1.0, which was obtained from a single-point energy calculation using the structure optimized for c 3 ϭ 0.8. At this exact exchange admixture of 100%, i.e., close to the Hartree–Fock value of the splitting, a new structure becomes the minimum for the singlet state. The energy splitting deviates surprisingly little from the linear relationship at small values of c 3 up to c 3 Ϸ 0.5. The energy splitting ⌬ E a / b from two different spin states S a and S b , ⌬ E ϭ E Ϫ E , ͑ 2 ...
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Citations
... The sidechain models of [4Fe-4S] and [2Fe-2S] clusters were optimized at unrestricted B3LYP* (B3LYP with 15% Hartree-Fock exchange) with the def2-TZVP basis set. B3LYP* has been shown to provide an accurate description of the electronic structure of iron-sulfur clusters (Salomon et al., 2002;Benediktsson & Bjornsson, 2022). An initial guess was generated based on a fragmentation approach, followed by a wavefunction's stability calculation. ...
The phosphorylation of photosystem II (PSII) and its antenna (LHCII) proteins has been studied, and its involvement in state transitions and PSII repair is known. Yet, little is known about the phosphorylation of photosystem I (PSI) and its antenna (LHCI) proteins.
Here, we applied proteomics analysis to generate a map of the phosphorylation sites of the PSI–LHCI proteins in Chlorella ohadii cells that were grown under low or extreme high‐light intensities (LL and HL). Furthermore, we analyzed the content of oxidized tryptophans and PSI–LHCI protein degradation products in these cells, to estimate the light‐induced damage to PSI–LHCI.
Our work revealed the phosphorylation of 17 of 22 PSI–LHCI subunits. The analyses detected the extensive phosphorylation of the LHCI subunits Lhca6 and Lhca7, which is modulated by growth light intensity. Other PSI–LHCI subunits were phosphorylated to a lesser extent, including PsaE, where molecular dynamic simulation proposed that a phosphoserine stabilizes ferredoxin binding. Additionally, we show that HL‐grown cells accumulate less oxidative damage and degradation products of PSI–LHCI proteins, compared with LL‐grown cells.
The significant phosphorylation of Lhca6 and Lhca7 at the interface with other LHCI subunits suggests a physiological role during photosynthesis, possibly by altering light‐harvesting characteristics and binding of other subunits.
... A close relationship between HS-LS energy balance with the amount of HFex term included in the DFT hybrid functionals was already described for transition metal complexes. [65][66][67][68] We observe a corresponding trend in the scatter data of Co(I)/Co(II) HS-LS energies shown in Fig. 3(b) where the HS-LS energy progression (BP86 > BLYP > TPSSh > B3LYP * > B3LYP) correlates well with the amount of HFex [BP86(0%), BLYP(0%) > TPSSh(10%) > B3LYP * (15%) > B3LYP(20%)]. Also, a comparison of the data shown in Fig. 3(c) for the hybrid functionals and 3d for the range-separated functional suggests that the range-separated functionals typically further favor the HS forms. ...
Photoredox properties of several earth-abundant light-harvesting transition metal complexes in combination with cobalt-based proton reduction catalysts have been investigated computationally to assess the fundamental viability of different photocatalytic systems of current experimental interest. Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations using several GGA (BP86, BLYP), hybrid-GGA (B3LYP, B3LYP*), hybrid meta-GGA (M06, TPSSh), and range-separated hybrid (ωB97X, CAM-B3LYP) functionals were used to calculate relevant ground and excited state reduction potentials for photosensitizers, catalysts, and sacrificial electron donors. Linear energy correction factors for the DFT/TD-DFT results that provide the best agreement with available experimental reference results were determined in order to provide more accurate predictions. Among the selection of functionals, the B3LYP* and TPSSh sets of correction parameters were determined to give the best redox potentials and excited states energies, ΔEexc, with errors of ∼0.2 eV. Linear corrections for both reduction and oxidation processes significantly improve the predictions for all the redox pairs. In particular, for TPSSh and B3LYP*, the calculated errors decrease by more than 0.5 V against experimental values for catalyst reduction potentials, photosensitizer oxidation potentials, and electron donor oxidation potentials. Energy-corrected TPSSh results were finally used to predict the energetics of complete photocatalytic cycles for the light-driven activation of selected proton reduction cobalt catalysts. These predictions demonstrate the broader usefulness of the adopted approach to systematically predict full photocycle behavior for first-row transition metal photosensitizer–catalyst combinations more broadly.
... This value was chosen to reproduce the optical absorption spectrum of the molecule as obtained from the LR-TDDFT calculations (see Fig. S2A and further details below). Our finding that a reduced α provides a better description of the Fe complex is consistent with previous observations that Fe coordination complexes are best described by such a reduced α parameter (41,42). The FHI-Aims code is an all-electron electronic structure code that uses numerically defined atom-centered orbitals. ...
The photoinduced switching of Fe(II)-based spin-crossover complexes from singlet to quintet takes place at ultrafast time scales. This a priori spin-forbidden transition triggered numerous time-resolved experiments of solvated samples to elucidate the mechanism at play. The involved intermediate states remain uncertain. We apply ultrafast x-ray spectroscopy in molecular films as a method sensitive to spin, electronic, and nuclear degrees of freedom. Combining the progress in molecule synthesis and film growth with the opportunities at x-ray free-electron lasers, we analyze the transient evolution of the Fe L3 fine structure at room temperature. Our measurements and calculations indicate the involvement of an Fe triplet intermediate state. The high-spin state saturates at half of the available molecules, limited by molecule-molecule interaction within the film.
... The software package of Gaussian 09 was applied for optimizing of the geometry of each compound [20]. Geometry was optimized using the B3LYP* method with c3 = 0.15 [21,22] and the standard 6-311G(d,p) basis set [23][24][25][26]. B3LYP* method is a new parametrization of the B3LYP functional. ...
In the present research, computational perspective of doping of C 20 nano-cage with Co ³⁺ , Ni ²⁺ , Cu ⁺ and Zn cations was reported at B3LYP*/6-311g(d,p) level of theory in singlet state. Vibrational analysis was confirmed placing of the optimized cluster of the minimum potential energy curve. M-C bond distances, molecular orbital analysis and electronic spatial extent (ESE) values of the clusters were computed. Photoelectron spectrum (PES) of these clusters were provided. Aromaticity of the studied clusters were compared with NICS values. Doping effect on the polarity, polarizability and hyperpolarizability of the cluster was illustrated.
... Past work has already indicated that the optimum HF percent for the prediction of transition metal compounds spin states depends on the metal type and ligand type. 17,71 Our results further show that even when holding the metal type fixed and using very similar ligands, this optimum is still highly sensitive to the sign and magnitude of magnetic coupling between the metallic atoms. ...
... However, the stronger static correlation in transition metal compounds 78,79 requires that more semi-local exchange be retained. This is in agreement with the findings of Reiher and co-workers, 15,17,71 who introduced B3LYP * , with a reduced fraction of 15%, as an alternative to B3LYP with the default of 20% for spin-crossover compounds (with similar findings made later for RSH functionals 80 ) and with reports of other more correlated systems benefiting from a reduction of the amount of exact exchange. [81][82][83] Again this optimum may be system-dependent (for example, one iron complex required 12% HF exchange 17 ) and our slightly lower values of 10%-11% may reflect an even stronger static correlation. ...
Reliable prediction of the ground-state spin and magnetic coupling constants in transition-metal complexes is a well-known challenge for density functional theory (DFT). One popular strategy for addressing this long-standing issue involves the modification of the fraction of Fock exchange in a hybrid functional. Here we explore the viability of this approach using three polynuclear metal-organic complexes based on a Ni4O4 cubane motif, having different ground state spin values (S = 0, 2, 4) owing to the use of different ligands. We systematically search for an optimum fraction of Fock exchange, across various global, range-separated, and double hybrid functionals. We find that for all functionals tested, at best there only exists a very narrow range of Fock exchange fractions which results in a correct prediction of the ground-state spin for all three complexes. The useful range is functional dependent, but general trends can be identified. Typically, at least two similar systems must be used in order to determine both an upper and lower limit of the optimal range. This is likely owing to conflicting demands of minimizing delocalization errors, which typically requires a higher percentage of Fock exchange, and addressing static correlation, which typically requires a lower one. Furthermore, we find that within the optimal range of Fock exchange, the sign and relative magnitude of Ni–Ni magnetic coupling constants are reasonably well reproduced, but there is still room for quantitative improvement in the prediction. Thus, the prediction of spin state and magnetic coupling in polynuclear complexes remains an ongoing challenge for DFT.
... ; https://doi.org/10.1101/2023.10.01.560385 doi: bioRxiv preprint 15% Hartree-Fock exchange) with the def2-TZVP basis set. B3LYP* has been shown to provide an accurate description of the electronic structure of iron-sulfur clusters (Salomon et al., 2002;Benediktsson & Bjornsson, 2022). An initial guess was generated based on a fragmentation approach, followed by a wavefunction's stability calculation. ...
The phosphorylation of photosystem II (PSII) and its antenna (LHCII) proteins has been extensively studied and its involvement in state transitions and PSII repair is well known. Yet, very little is known about the extent and functions of phosphorylation of photosystem I (PSI) and its antenna (LHCI) proteins. Here, two proteomics methods were applied to generate a detailed map of the phosphorylation sites of the PSI-LHCI proteins in Chlorella ohadii cells that were grown under low- or extreme high-light intensities (LL and HL). Furthermore, we analyzed the content of oxidized tryptophans in these cell types to estimate light-induced oxidative damage to PSI-LHCI.Our work revealed the phosphorylation of 11 out of 22 PSI-LHCI subunits. The analyses detected extensive phosphorylation of the LHCI subunits lhca6 and lhca7. Other PSI-LHCI subunits were phosphorylated to a lesser extent. Additionally, we show the accumulation of oxidatively damaged tryptophans in the psaD subunit of PSI of HL-grown C. ohadii. The significant phosphorylation of lhca6 and lhca7 suggests a physiological role during photosynthesis, possibly by altering light-harvesting characteristics and binding of other LHCI subunits. Moreover, we show that psaD is susceptible to photodamage while LHCI is protected from ROS under HL.
... To optimize the structure DFT computation was carried out with the help of the Gaussian 09 [52] program. The ground state geometries of the HL and complex 1 are measured in methanol whereas the complex 1picric acid adduct are fully optimized in DMSO-water solvent using B3LYP [53] exchange-correlation functional, 6-311 + G(d,p) basis set for all non-metallic atoms, and Lanl2dz basis set and respective effective core potential for the metal atoms, as implemented in Gaussian 16 program package. Considering the floppy structure of some of the systems, tight convergence criteria along with an ultrafine grid for integral calculations and empirical dispersion (GD3) to account for dispersion interactions are used. ...
... Optimization of complexes was performed by B3LYP* technique, with c3 = 0.15 (Parr and Yang 1989;Salomon et al. 2002) and the 6-311G(d,p) basis set (Hay 1977;Krishnan et al. 1980;McLean and Chandler 1980;Wachters 1970;Pritchard et al. 2019;Feller 1996;Schuchardt et al. 2007) using Gaussian 09 suite (Frisch et al. 2009). The method is a parametrization of the B3LYP functional, with 15% Hartree-Fock exchange, rather than 20% in B3LYP. ...
The current investigation, interaction of Cr(CO)3 fragment with corannulene was examined at the B3LYP*/6-311G(d,p) level of theory. C-PCM study of the formed Cr(CO)3(η⁶- corannulene) complex was reported. Independent and dependent-frequency isotropic polariazability and first hyperpolarizability values of this complex were calculated. The solvent effect on these data were examined using conductor polarizable continuum model (C-PCM). Correlations of the energetics, electronic and optical properties with modified-Buckingham function (Fmodified-Buckingham) were illustrated. Reduced density gradient (RDG) was employed to analyze the interaction between Cr(CO)3 fragment with corannulene.
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Some 2H-chromen-2-one and imine derivatives have been synthesized through a one-pot condensation of aldehydes, diethyl malonate, and amine compounds. The compounds obtained have been characterized using FTIR, NMR, GC-MS, and elemental analysis. The single-crystal X-ray structure of 3-[piperidine-1-carbonyl]-2H-chromen-2-one (2) has been presented. Compound 2, recrystallized in the monoclinic space C2/c (no. 15), a = 16.654(15) Å, b = 8.789(7) Å, c = 18.460(18) Å, β = 102.89(5)°, V = 2634(4) Å3, Z = 8, T = 296(2) K, μ(MoKα) = 0.091 mm-1, Dcalc = 1.298 g/cm3, 17626 reflections measured (4.528° ≤ 2Θ ≤ 57.446°), 3321 unique (Rint = 0.0313, Rsigma = 0.0257) which were used in all calculations. The final R1 was 0.0441 (I > 2σ(I)) and wR2 was 0.1329 (all data). The experimental bond lengths, bond angles, and other topological properties of compound 2 were compared with the DFT calculated results, the comparison showed good agreement with each other with varying level deviations. The energy levels of HOMO and LUMO, as well as the global chemical reactivity descriptors of representative compound 2, have been presented. A discussion of the Hirshfeld surface analysis of compound 2 has been carried out to provide insight into its structural properties.
... These calculations utilized the scalar all-electron zeroth-order regular approximation (ZORA) [59] in combination with the spin-unrestricted formalism. The hybrid functionals, PBE0 [60,61] (Perdew-Burke-Ernzerhof) with 25% of exact Hartree-Fock exchange (HFX), B3LYP [62][63][64][65] (Becke, three-parameter Lee-Yang-Parr) with 20% of HFX, and B3LYP* [66] with 15% of HFX, were employed along with the triple-ζ polarized Slater-type orbital (STO) all-electron basis set, with one set of polarization function for all the atoms (TZP) [67]. ...
Assembling metallacycles with interesting topological arrangements is a critical task for chemists. We report here a novel dodecanuclear CuII compound, [{Cu3L(µ-N3)}4(Py)14]·2Py (Cu12) (where Py = pyridine and [H6L]Cl = tris(2-hydroxybenzylidine)triaminoguanidinium chloride, respectively), with the topology of a cycle accomplished by four two-connecting approximately flat C3-symmetric guanidine-based ligands. Each ligand affords three tridentate metal-binding cavities and the four node-to-node connections through single azido bridges are provided by pairs of metal centers. A theoretical investigation using CASSCF in addition to DFT calculations showed strong antiferromagnetic coupling within the Cu3-triangles, resulting in spin-frustrated systems. However, these calculations were not able to properly reproduce the very weak antiferromagnetic couplings between the triangle units, highlighting the challenge of describing the magnetic behavior of this compound.
