Structure, Vibrations and Raman Modes in Electron Doped Metal Phthalocyanines

Abstract

Identifying and understanding the vibrational frequency shifts caused by electron addition to metal phthalocyanine (MPc) molecules is the main goal of the present work. Among other things, it should be useful in establishing the amount of charge-transfer level recently reported in potassium doped solid MPc films. Choosing MgPc as our working case, we calculated by density functional methods the full vibration spectrum of the neutral and of the negatively charged molecule, with and without Jahn-Teller distortion. In the negative ion MgPc- we found that although individual modes behave differently, the generality of modes undergoes a negative frequency shift of about 10 cm(-1) for a single extra electron added in the eg affinity level. We calculated the Raman intensities and made qualitative connection with recent data on K-doped CuPc films. The detailed features and parameters of the static Jahn-Teller effect in a phthalocyanine molecular ion are obtained as a byproduct.

Ultrafast Charge Transfer in Nickel Phthalocyanine Probed by Femtosecond Raman-Induced Kerr Effect Spectroscopy

“…62–66 Instead, enhancement of non-totally symmetric modes is attributable to a Jahn–Teller (J-T) effect in the doubly degenerate π - π * excited state. 67–70 …”

“…This state was computed 21 to lie only 0.24 eV above the S 1 state, vertically, and relaxation might lower it below S 1 , providing an efficient deactivation route. The Pc orbitals are of e g symmetry, and their excitation would produce a J-T distortion, 67–70 facilitated by the B g modes that are enhanced in the FRIKES spectrum. The breadth of the species 1 bands, and their depressed frequencies, are consistent with a dynamic J-T effect, as the degenerate π orbitals interconvert.…”

Molecular Structure, Optical and Magnetic Properties of Dianionic Free‐Base Tetrapyrazinoporphyrazine Macrocycle

“…We can assume that population of LUMO and LUMO+1 orbitals has an additive effect on bond lengths. Disruption of aromaticity due to the formation of less stable 20 π‐electron system of the dianion (in comparison with stable aromatic 18 π‐electron system of pristine H 2 TPyzPz) and the Jahn‐Teller distortions, can also contribute to the distortion of the H 2 TPyzPz macrocycle.…”

Salts with titanyl and vanadyl phthalocyanine radical anions. Molecular design and effect of cations on the structure and magnetic and optical properties

“…The reason for the bond alternation can be clearly explained in terms of the Jahn-Teller (JT) theory. According to the theoretical works [44][45][46] the calculated potential surface of phthalocyanine radical anions has four special points: two equivalent minima and two saddle points (two barriers between these minima). The potential minima correspond to rectangular deformations of the Pc macrocycles while transition states correspond to rhombic ones.…”