Volatile Heterobimetallic Complexes from Pd-II and Cu-II beta-Diketonates: Structure, Magnetic Anisotropy, and Thermal Properties Related to the Chemical Vapor Deposition of Cu-Pd Thin Films

Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. A novel approach for preparing volatile heterometallic complexes for use as precursors for the chemical vapor deposition of various materials is reported. New CuPd complexes based on β-diketonate units were prepared, and their structures and compositions were determined. [PdL2∗CuL2] (1) and [PdL2∗Cu(tmhd)2] (2) (L=2-methoxy-2,6,6-trimethylheptane-3,5-dionate; tmhd=2,2,6,6- tetramethylheptane-3,5-dionate) are 1D coordination polymers with alternating metal complexes, which are connected through weak interactions between the Cu atoms and the OCH3 groups from the ligand of the Pd complexes. The volatility and thermal stability were studied using thermogravimetric and differential thermal analyses and mass spectrometry. Compound 1 vaporizes without decomposition into monometallic complexes. It exhibits magnetic anisotropy, which was revealed from the angular variations in the EPR spectrum of a single crystal. The vapor thermolysis process for 1 was investigated using mass spectrometry, allowing the process to be framed within the temperature range of 200-350C. The experimental data, supported by QTAIM calculations of the allowed intermolecular interactions, suggest that 1 likely exists in the gas phase as bimetallic molecules. Compound 1 proved to be suitable as a single-source precursor for the efficient preparation of CuPd alloy films with tunable Cu/Pd ratio. A possible mechanism for the film growth is proposed based on the reported data. Making a chain: Linking metal β-diketonates to form a heterometallic linear coordination polymer resulted in the convenient, scalable synthesis of a new family of volatile heterometallic compounds. Their properties are tuned by the rational design of the ligand structure and matching of central atoms. A CuPd complex of this type (see figure) is volatile and can be a promising precursor for bimetallic alloy films prepared by chemical vapor deposition.

Publication year:2015