Theoretical and experimental study on the excited states of the X-, α- and β-forms of lithium phthalocyanine

DFT study of electron absorption and emission spectra of pyramidal LnPc(OAc) complexes of some lanthanide ions in the solid state

The electron absorption and emission spectra were measured for the pyramidal LnPc(OAc) complexes in the solid state and co-doped in silica glass, where Ln=Er, Eu and Ho. The theoretical electron spectra were determined from the quantum chemical DFT calculation using four approximations CAM-B3LYP/LANL2DZ, CAM-B3LYP/CC-PVDZ, B3LYP/LANL2DZ and B3LYP/CC-PVDZ. It was shown that the best agreement between the calculated and experimental structural parameters and spectroscopic data was reached for the CAM-B3LYP/LANL2DZ model. The emission spectra were measured using the excitations both in the ligand and lanthanide absorption ranges. The possibility of energy transfer between the phthalocyanine ligand and excited states of lanthanide ions was discussed. It was shown that the back energy transfer from metal states to phthalocyanine state is responsible for the observed emission of the studied complexes both in the polycrystalline state and silica glass.

Theoretical study on crystal polymorphism and electronic structure of lead(ii) phthalocyanine using model dimers

The polymorphism in lead(ii) phthalocyanine solids was discussed with the results of density functional theory calculations using small models.

DFT study of the potential energy surfaces towards the searching of the stable self-assembled phthalocyanine dimers

We have applied the density functional theory (DFT) to find stable dimeric structures on the potential energy surfaces (PESs) of slippage, tilting and rotation of the macrocycles of monohydroxy magnesium phthalocyanine complex. Gradual changing of a distance between Mg 2+ ions and oxygen atoms of the OH -groups, as well as the dihedral angles between the planes passing through the isoindoline nitrogen atoms of different macrocycles has allowed finding of six stable dimeric structures that differ from each other by the spatial arrangement of the macrocycles. The most stable structure was found for the dimer in which two equivalent low-symmetry phthalocyanine macrocycles are double fixed by the coordination bonds between the complexing metal ions and oxygen of the OH -groups. This result is in agreement with our earlier experimental data.

Theoretical study on the stability of double-decker type metal phthalocyanines, M(Pc)2 and M(Pc)2(+) (M = Ti, Sn and Sc): a critical assessment on the performance of density functionals

We report the results of theoretical calculations on the optimized structures and relative energies between the D4d and D2 symmetry structures for double-decker type phthalocyanine compounds, Ti(Pc)2, Ti(Pc)2(+), Sn(Pc)2, Sn(Pc)2(+), Sc(Pc)2 and Sc(Pc)2(+), using eighteen types of functionals: B3LYP, B3PW91, B3P86, PBE1PBE, BHandHLYP, BPW91, BP86, M06, M06-2x, M06-HF, M06L, LC-BPW91, LC-ωPBE, CAM-B3LYP, B97D, ωB97, ωB97X and ωB97XD. Two phthalocyanine moieties are stacked in a face-to-face configuration in the D4d structure, but they are stapled by two σ-bonds in the D2 one. We found that the molecular symmetry of M(Pc)2 and M(Pc)2(+) depends on the balance between stabilization due to electron delocalization and exchange repulsion of π-electrons in the phthalocyanine moieties. We assessed the performance of the well-established functionals to select the appropriate functional for calculations on M(Pc)2 and M(Pc)2(+), and several important aspects came out. Generally, the hybrid GGA and hybrid meta-GGA functionals with 20-27% of the HF exchange term would give the molecular structures consistent with the experimental expectations for the double-decker type phthalocyanine compounds. Pure GGA and pure meta-GGA functionals (BPW91, BP86, M06L and B97D) have the tendency to overestimate the stability of the D4d structure. On the other hand, functionals including HF exchange for 50% and over or including long-range corrections (BHandHLYP, M06, M06-2x, M06-HF, LC-BPW91, LC-ωPBE, CAM-B3LYP, ωB97, ωB97X and ωB97XD) tend to overestimate the stability of the D2 structure. It should be emphasized that the B3LYP functional, one of the most commonly used hybrid GGA functionals with 20% HF exchange, cannot estimate the relative stability between the two molecular structures of Ti(Pc)2 appropriately. The calculation for the systems considered in this article required well-balanced treatment of the HF exchange with the accompanied exchange-correlation functional. Thus, as has been pointed out rigorously and frequently, the selection of the functional is a crucial point for reliability of the calculations.

Theoretical and experimental investigation on the electronic properties of the shuttlecock shaped and the double-decker structured metal phthalocyanines, MPc and M(Pc)2 (M = Sn and Pb)

The molecular geometries, electronic structures, and excitation energies of tin and lead phthalocyanine compounds, SnPc, PbPc, Sn(Pc)(2), and Pb(Pc)(2), were investigated using the B3LYP method within a framework of density functional theory (DFT). The geometries of SnPc, PbPc, Sn(Pc)(2), and Pb(Pc)(2) were optimized under C(4v), C(4v), D(4d), and D(4d) molecular symmetries, respectively. The excitation energies of these molecules were computed by the time-dependent DFT (TD-DFT) method. The calculated results for the excited states of three compounds other than the unknown Pb(Pc)(2) corresponded well with the experimental results of electronic absorption spectroscopy. The non-planar C(4v) molecular structure of SnPc and PbPc influences especially on the orbital energy of the HOMO-1 through mixing of the s-type atomic orbital of the central metal atom to the π system of the Pc ring in an anti-bonding way; however, the HOMO and the LUMO have little effect of the deviation from the planar structure because they have no contribution from the atomic orbital of the central metal. This orbital mixing pushes up the orbital energy of the HOMO-1, and reduces the energy of the metal-to-ligand charge transfer band of SnPc and PbPc. The calculated results also reproduced well the excitation profile of Sn(Pc)(2), which was quite different from that of SnPc. The strong interactions between the π-type orbitals of two Pc moieties altered the electronic structure resulting in the characteristic excitation profile of Sn(Pc)(2). In addition, this caused a reduction of about 0.8 eV in the ionization potential as compared to usual MPcs including SnPc, which was consistent with the experimental results.