Quantum chemical replica-exchange umbrella sampling molecular dynamics simulations reveal the formation mechanism of iron phthalocyanine from iron and phthalonitrile

Shingo Ito, Ying Wang, Yuko Okamoto, Stephan Irle

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Abstract

Phthalocyanine (Pc) and its metal complexes (MPcs) have been used industrially since their discovery in the early 20th century. The phthalonitrile (PN) method is a well-known synthesis method in which Pc or MPc can be afforded by heating a mixture of PN and metal powders over 280 °C with only moderate yield. However, the formation mechanism of the phthalocyanines and the intermediate stages of this seemingly simple reaction have yet to be fully understood. To study this mechanism computationally, we carried out quantum chemical molecular dynamics (MD) simulations based on the density-functional tight-binding (DFTB) method, applying the replica-exchange umbrella sampling (REUS) method, starting from four PN molecules and one iron atom. The DFTB-REUS-MD simulations successfully yielded FePc, and a metastable structure very similar to FePc but with a reactive nitrene unit was also identified that might explain the incomplete conversion of the reactants into FePc. Analysis of the MD trajectories reveals a three-step FePc formation mechanism for the PN method.

Original languageEnglish
Article number072332
JournalJournal of Chemical Physics
Volume149
Issue number7
DOIs
StatePublished - Aug 21 2018

Funding

Some of the computations were performed on the supercomputers at the Institute for Molecular Science and at the Information Technology Center, Nagoya University. This work was supported, in part, by the Grants-in-Aid for Scientific Research (S) (No. JP16H06353), (A) (No. JP25247071), and the Grants-in-Aid for Scientific Research on Innovative Areas “Dynamical Ordering and Integrated Functions” (No. JP25102009). S. Irle was supported in part by the Laboratory Directed Research and Development (LDRD) Program of Oak Ridge National Laboratory. ORNL is managed by UT-Battelle, LLC, 651 for DOE under Contract No. DE-AC05-00OR22725.

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