Molecular Structures of Phthalocyaninatozinc and Hexadecafluorophthalocyaninatozinc Studied by Gas-Phase Electron Diffraction and Quantum Chemical Calculations

Abstract

The molecular structures of phthalocyaninatozinc (HPc-Zn) and hexadecafluorophthalocyaninatozinc (FPc- Zn) are determined using the gas electron diffraction (GED) method and high-level density functional theory (DFT) quantum chemical calculations. Calculations at the B3LYP/6-311++G** level indicate that the equilibrium structures of HPc-Zn and FPc-Zn have D4h symmetry and yield structural parameters in good agreement with those obtained by GED at 480 and 523 degrees C respectively. The calculated force fields indicate that both molecules are flexible. Normal coordinate calculations on HPc-Zn yield five vibrational frequencies (one degenerate) in the range 22-100 cm(-1), and ten vibrational frequencies ranging from 13 to 100 cm(-1) (three degenerate) for FPc-Zn. The high-level force field calculations confirm most of the previous vibrational assignments, and some new ones are suggested. The out-of-plane vibration of the Zn atom in HPc-Zn was studied in detail optimizing models in which the distance from the Zn atom to the two symmetry equivalent diagonally opposed N atoms (h) was fixed. The calculations indicate that the vibrationally activated vertically displacement of the Zn atom is accompanied by distortion of the ligand from D4h to C2v symmetry. The average height, h, at the temperature of the GED experiment was calculated to be 14.5 pm. Small structural changes indicate that a full F substitution on the benzo-subunits do not significantly alter the geometry, however there are indications that the benzo-subunits may shrink slightly with perfluorination.

Solvent impact on the planarity and aromaticity of free and monohydrated zinc phthalocyanine: a theoretical study

“…It is worth mentioning that the recent X-ray studies [26] on three axial ZnPc•••n-alkylamines nicely agree with our data and prove the existence of similar nonplanar structures with d parameter of about 0.5 Å. In addition, the subsequent B3LYP/6-31+G(d) [70] b HF, B3LYP, and MP2 with 6-31G* result from [41] c UB3LYP/6-31G(d,p) data for ZnPc, from [71] d B3LYP/6-31G** data from [34] e B3LYP/6-31G* data for ZnPc, from [72] f X-ray data for ZnPc, from [20] g ED data from [21] h Reinvestigation of ED data from [22] i ED data for SnPc, from [22] j ED data for MgPc, from [22] k Laser-desorption supersonic jet spectroscopy data for H2Pc with D 2h symmetry; planar are also MgPc and ZnPc with D 4h symmetry, from [27] l ED data from [35] [75] e X-ray data for ZnPc•••n-hexylamine, from [24] calculations by these authors [26] closely reproduced the observed crystal structure of these solvates (d was about 0.43 Å …”

“…In 1999, Fink and co-workers [22] reported on both gas-phase electron diffraction and theoretical DFT studies on the planar equilibrium structure of ZnPc while the BLYP/6-31G* and BLYP/6-31G** data produced a nonplanar molecule with zinc ion about 0.075 Å above the ligand plane [34]. Another experimental electron diffraction and DFT study proposed a planar structure of ZnPc [35]. These authors also obtained a planar D 4h structure using B3LYP density functional and large basis sets of 6-311++G** and cc-pVTZ quality.…”

Accurate molecular structure of copper phthalocyanine (CuN8C32H16) determined by gas-phase electron diffraction and quantum-chemical calculations

“…Despite intensive investigations of these compounds by different methods, at present the molecular structures of only five nonsubstituted metal phthalocyanine MPc, where M = Sn, Mg, Zn, Cu, and Ni, were studied by gas-phase electron diffraction (GED) method [5][6][7]. The first gasphase structure of CuPc complexes determined by gas electron diffraction was published more than 10 years ago [5].…”

“…In the studies of the aforementioned compounds, the authors [5][6][7] paid special attention to the determination of the position of the metal ion relative to N 8 C 8 plane of ring. For complex SnPc [5] the displacement of the metal ion out of the plane of the phthalocyanine fragment was found to be 1.0(1) Å .…”

Theoretical Study of Oxozirconium Porphyrin, Octamethylporphyrin, Porphyrazine and Phthalocyanine Complexes

“…Such level of theory has been found to yield accurate structural parameters in earlier combined (experimental and theoretical) studies of oxotitanium phthalocyanine [2] and other large macroheterocyclic molecules. [16][17][18][19][20] Singlet and triplet excited states and the electronic spectra were studied using time-dependent density functional theory (TDDFT) implemented in PC GAMESS 7.0. [9] In all four molecules the molecular orbitals formed mostly by 1s orbitals of C, N, and O atoms, namely 25 first (lowest energy) orbitals in oxozirconium porphyrin and porphyrazine, 33 in octamethylporphyrin and 41 in phthalocyanine, were excluded ("frozen") from the TDDFT calculations.…”