Proposal of new QM/MM approach for geometry optimization of periodic molecular crystal: Self-consistent point charge representation for crystalline effect on target QM molecule

Aono, Shinji; Sakaki, Shigeyoshi

doi:10.1016/j.cplett.2012.06.045

Cited by 7 publications

(17 citation statements)

References 18 publications

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“…Thus, a theoretical approach is necessary because it is expected to provide us with valuable information of the excited state of the transition-metal complex in the crystal. In this regard, several theoretical studies of the 3 MMLCT excited state have been reported so far. − However, the crystal effect has not been taken into consideration in most of those studies except for one recent work in which crystal effects were considered in the calculation by the periodic QM/MM method …”

Section: Introductionmentioning

confidence: 99%

“…17−24 However, the crystal effect has not been taken into consideration in most of those studies except for one recent work 24 in which crystal effects were considered in the calculation by the periodic QM/MM method. 25 The other interesting photoproperty is temperature effect on the spectrum. One good example is found in the emission spectrum of the cyclometalated platinum(II) complex; this is phosphorescent in acetonitrile solution at both low temperature (LT) and room temperature (RT), while its palladium-(II) analogue is emissive only at LT in the solid state and grassy acetonitrile.…”

Section: Introductionmentioning

confidence: 99%

“…The calculation of such a large unit cell is not easy even using the periodic DFT method. One promising computational approach is the use of the periodic QM/MM method with self-consistent charge distribution 25 because this method is able to calculate the target molecule at the excited state using the QM method in the presence of many MM molecules at the ground state.…”

Section: Introductionmentioning

confidence: 99%

“…To incorporate the crystal effect into theoretical calculation, we employed the periodic QM/MM method with self-consistent charge distribution. 25 In this method, several Pt complexes were calculated at the QM level and the surrounding Pt complexes were treated at the MM level using the Lennard-Jones (LJ) potentials and point charge distribution. Geometry and point charge distribution of the surrounding MM molecules were taken to be the same as DFT-optimized geometry and DFT-calculated electrostatic potential (ESP) charges of the QM molecule at the ground state in crystal, respectively.…”

Section: Introductionmentioning

confidence: 99%

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Delocalization of the Excited State and Emission Spectrum of the Platinum(II) Bipyridine Complex in Crystal: Periodic QM/MM Study

et al. 2020

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The emission spectrum of the platinum(II) bipyridine complex [Pt-(CN) 2 (bpy)] (bpy = 2,2′-bipyridine) interestingly exhibits blue shift and peak broadening in crystal as temperature increases from 15 to 292 K. Periodic QM(DFT)/MM calculations here showed that the emission spectrum was assigned as metal−metal to ligand charge transfer triplet ( 3 MMLCT) excited state in which one-electron excitation occurred from d σ −d σ antibonding molecular orbital (MO) between several Pt atoms to the bpy π* orbital. Although the elongation of the Pt−Pt distance by the temperature rise was experimentally observed at the ground state, the QM/MM calculations indicated that the Pt−Pt distance at the 3 MMLCT excited state did not change so much by the temperature rise. The broadening of the emission spectrum by the temperature rise was reproduced by taking account of thermal population of vibrationally excited states of Pt−Pt stretching at the 3 MMLCT excited state. The blue shift of the emission peak by the temperature rise was explained by the thermal population of several possible structures at the 3 MMLCT excited state; in the most plausible structure, two Pt(II) complexes participate in the 3 MMLCT excited state (named 3 [Pt] 2 ), and in the second and the third ones, three and four Pt(II) complexes, respectively, participate in the excited state (named 3 [Pt] 3 and 3 [Pt] 4 ). Interestingly, 3 [Pt] 4 is more stable than 3 [Pt] 2 and 3 [Pt] 3 in the crystal structure at low temperature (LT = 10 K) but 3 [Pt] 3 is the most stable in the crystal structure at room temperature (RT = 293 K) because of the difference in the crystal structure. Considering thermal populations of these species, the emission peak was calculated at 1.95 eV in the LT crystal structure and 2.01 eV in the RT crystal structure, which agree well with the experimental values (1.87 and 1.94 eV at 15 and 292 K, respectively). These findings indicate that populations of the vibrationally excited state and several possible structures at the 3 MMLCT exited state are crucially important for correctly understanding the emission spectrum in crystal.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Delocalization of the Excited State and Emission Spectrum of the Platinum(II) Bipyridine Complex in Crystal: Periodic QM/MM Study

et al. 2020

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“…In the present study, we theoretically investigated the geometries of these molecular crystals, CH−π and π–π interactions, and absorption and emission spectra of 1 and 2 in crystal to present assignments of those spectra under consideration of crystal effects and to elucidate the reason why those spectra differ significantly between two different polymorphic crystals . To incorporate the crystalline effects, we employed the quantum mechanics/molecular mechanics (QM/MM) method based on the periodic MM crystal model with the self-consistent point charges. , In our method, QM molecule is embedded in infinitely periodic MM crystal, the point charges and geometries of which are determined as mirror image of the QM molecule in the self-consistent field (SCF) manner by applying the translational and symmetrizing operations to the subunit of the minimum unit cell. One of the strong points of our method is to construct the periodic MM crystal model in the closed-shell singlet ground state, assuming that all of the symmetrically minimal subunits have the same structures and charge distributions.…”

Section: Introductionmentioning

confidence: 99%

Dependence of Absorption and Emission Spectra on Polymorphs of Gold(I) Isocyanide Complexes: Theoretical Study with QM/MM Approach

et al. 2019

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We theoretically investigated phenyl(phenyl isocyanide) gold(I) (PhNC)Au(Ph) 1 and phenyl(dimethylphenyl isocyanide) gold(I) (dimPhNC)Au(Ph) 2 in crystal using our periodic quantum mechanics/molecular mechanics (QM/MM) method based on the self-consistent point charges to elucidate interesting mechano-chemical changes of absorption and emission spectra of 1 and 2 in crystal. To characterize 1 and 2 in crystal, their absorption and emission spectra in crystal were compared to those in gas phase and CHCl3 solvent, where a three-dimensional reference interaction site model self-consistent field (3D-RISM-SCF) was employed to incorporate solvation effect. To investigate the phosphorescence spectrum in crystal, we optimized the geometry of the molecule at the triplet state in crystal which had ground-state geometry because the population of the excited state is generally very small. The QM/MM calculations showed that 1 formed two polymorphs 1b and 1y, 2 formed two polymorphs 2b and 2g, and 1y was more stable than 1b, which agree with the experimental findings. In 1b and 2b, the ligand-to-ligand charge transfer state is the lowest-energy excited state in the absorption, and the π–π* locally excited state on the PhNC moiety is the lowest-energy triplet state in the emission. In 1y and 2g, on the other hand, the metal–metal-to-ligand charge transfer (MMLCT) state is the lowest-energy excited state in both absorption and emission. These characteristic differences between two crystal structures arise from the geometrical features that the Au–Au distance is much shorter in 1y and 2g than in 1b and 1y and the intermolecular torsion angle η between two Au-PhNC moieties is much smaller in 1y and 2g than in 1b and 2b, respectively; the short Au–Au distance raises the energy level of antibonding orbital consisting of two Au dσ orbitals, and the small η angle lowers the energy level of bonding orbital consisting of two PhNC π* orbitals, leading to the presence of a lower-energy MMLCT state. The QM/MM calculations also disclosed intramolecular torsion angle τ between the Ph and PhNC planes and CH−π interaction of the Ph plane significantly influence absorption spectrum. Based on those computational results, discussion is presented on the differences in absorption and emission spectra among gas, solution, and crystal, the assignments of experimentally observed excitation and emission spectra in crystal, and their energy shifts induced by single-crystal-to-single-crystal phase transition.

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Approach of Electronic Structure Calculations to Crystal

Nakatani

Zheng

Sakaki

2023

The Materials Research Society Series

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Nowadays, the importance of molecular crystals and solids with regular structures is increasing in both basic chemistry and applied fields. However, theoretical studies of those systems based on electronic structure theories have been limited. Although density functional theory (DFT) calculations using generalized gradient approximation type functional under periodic boundary condition is effective for such theoretical studies, we need some improvements for calculating the dispersion interaction and the excited state of crystals. Accordingly, in this chapter, two methods for calculating the electronic structures of molecular crystals are discussed: cluster-model/periodic-model (CM/PM)-combined method and quantum mechanics/periodic-molecular mechanics (QM/periodic-MM) method. In the CM/PM-combined method, an infinite crystal system is calculated by the DFT method under periodic boundary condition, and important moieties, which are represented by CMs, are calculated by either DFT method with hybrid-type functionals or wave function theories such as the Møller–Plesset second-order perturbation theory (MP2), spin-component-scaled-MP2, and coupled-cluster singles and doubles theory with perturbative triples (CCSD(T)). This method is useful for gas adsorption into crystals such as metal–organic frameworks. In the QM/periodic-MM method, an important moiety is calculated using a QM method such as the DFT method with hybrid-type functionals and wave function theories, where the effects of the crystal are incorporated into the QM calculation via the periodic MM method using a classical force field. This method is useful for theoretical studies of excited states and chemical reactions. The applications of these methods in the following processes are described in this chapter: adsorption of gas molecules on metal–organic frameworks, chemical reactions in crystals, and luminescence of the crystals of transition metal complexes. To the best of our knowledge, the theoretical calculations conducted in this chapter show one of the successful approaches of electronic structure theories to molecular crystals, because of the reasonable and practical approximations.

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Proposal of new QM/MM approach for geometry optimization of periodic molecular crystal: Self-consistent point charge representation for crystalline effect on target QM molecule

Cited by 7 publications

References 18 publications

Delocalization of the Excited State and Emission Spectrum of the Platinum(II) Bipyridine Complex in Crystal: Periodic QM/MM Study

Delocalization of the Excited State and Emission Spectrum of the Platinum(II) Bipyridine Complex in Crystal: Periodic QM/MM Study

Dependence of Absorption and Emission Spectra on Polymorphs of Gold(I) Isocyanide Complexes: Theoretical Study with QM/MM Approach

Approach of Electronic Structure Calculations to Crystal

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