Raman spectra study of p-tert-butylphenoxy-substituted phthalocyanines with different central metal and substitution positions

Metallophthalocyanine (MPc) derivatives show excellent photoelectric and magnetic properties due to their large π-conjugate system. Central metals and peripheral substituents are two important ways to adjust and optimize the properties of MPc via tuning the large π-conjugate system. In this work, Raman scattering spectra of MPc, including ZnPc, CuPc, CoPc, and NiPc, were investigated. The most intense band in the Raman spectra at about 1500 cm−1, owing to the vibration of CNC bridge bonds, shifts significantly with the size of the metal ion, indicating a good marker of metal ion effect on the changes of the Raman shift. For the MPc with suitable sizes of metal ions (e.g., Zn2+, Cu2+, Co2+, Ni2+), the structure of phthalocyanine ring is planar. The ring will be distorted according to the different forces of the central metal ions. When the polarization force of the central metal ion enhances (Zn2+ < Cu2+ < Co2+ < Ni2+), the Raman shift of CNC would simultaneously increase, and the bigger polarization force could lead to a larger Raman shift (ZnPc < CuPc < CoPc < NiPc). On the other hand, the CNC Raman shift of the 3-substituted MPc was relatively smaller than that of the 4-substituted one with the same central metal ion. When the electron density of the phthalocyanine ring was relatively low, the energy of the system would increase and the Raman peak would correspondingly shift distinctly. Our Raman spectra results are consistent with the UV-vis measurement results. This work will provide the basis for structure analysis, and design of new molecular materials, as well as their application.