Syntheses, crystal structures, and physical properties of new cyanamides and carbodiimides of the magnetic 3d transition metals
Zusammenfassung der Projektergebnisse
Based on the successful synthesis and characterization of two classes of nitrogen-based pseudo-hydroxide and pseudo-oxide materials, that is, transition-metal hydrocyanamides such as M(NCNH)2 with M = Fe, Co, and Ni, and transition-metal carbodiimides of the form MNCN with M = Mn, Fe, Co, Ni, and Cu, we have continued to carry out additional syntheses, characterization steps and physical measurements of the structural and other properties using various analytical methods such as X-ray and neutron scattering, SQUID measurements, spectroscopic methods such as nuclear magnetic resonance (NMR) and electronspin resonance (ESR). In addition, systematic theoretical contributions using density-functional calculations including explicit electronic correlation (of the GGA+U type) and many-body theory have been performed to explain the magnetic, optical and other physical properties. Finally, we have synthesized the first 3d phase with fewer than five leftover valence electrons, the carbodiimide CrNCN, the first ferromagnetic M(III) 3d transition-metal carbodiimide, Cr2(NCN)3, and other interesting compounds such as a luminescent carbodiimide doped with europium. CuNCN, on the other hand, seems to adopt a resonating valence-bond ground state, a totally unforeseen result of fundamental importance for the entire solid-state field. Additional (spin-polarized) neutron-diffraction measurements of similar materials have been carried out. All that was meant to finalize this kind of research, as requested by DFG. Summarizing, we have made in-depth studies of these transition-metal nitrogen-based compounds. Whether this material class has a bright future or not remains to be seen, in particular with respect to commercial applications (e.g., luminescence). Based on the synthetic contributions, a purely theoretical DFG follow-up project has been granted, targeted at the many-body quantum theory of the 3d carbodiimides.
Projektbezogene Publikationen (Auswahl)
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Electronic and Magnetic Structure of Transition-Metal Carbodiimides by Means of GGA+U Theory. J. Phys. Chem. A 2010, 114, 12345– 12352
H. Xiang, R. Dronskowski, B. Eck, A. L. Tchougréeff
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Crystal Structure Refinement of M(NCNH)2 (M = Fe, Co) Based on Combined Neutron and X-ray Diffraction Data. Z. Anorg. Allg. Chem. 2011, 637, 1089–1091
X. Tang, A. Houben, X. Liu, L. Stork, R. Dronskowski
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Unconventional Magnetism in a Nitrogen-Containing Analog of Cupric Oxide. Phys. Rev. Lett. 2011, 107, 047208-1–047208-4
A. Zorko, P. Jeglič, A. Potočnik, D. Arčon, A. Balčytis, Z. Jagličič, X. Liu, A. L. Tchougréeff, R. Dronskowski
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α-SrNCN:Eu2+ – A Novel Efficient Orange-Emitting Phosphor. Chem. Mater. 2011, 23, 1694–1699
M. Krings, G. Montana, R. Dronskowski, C. Wickleder
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Structural Study of CuNCN and Its Theoretical Implications: A Case of a Resonating-Valence-Bond State? J. Phys. Chem. Lett. 2012, 3, 3360–3366
A. L. Tchougréeff, X. Liu, P. Müller, W. Van Beek, U. Ruschewitz, R. Dronskowski
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Syntheses, Crystal Structures and Magnetic Properties of Cr(NCNH2)4Cl2 and Mn(NCNH2)4Cl2. Z. Naturforsch. B 2012, 67, 1205– 1211
X. Tang, M. Speldrich, A. L. Tchougréeff, R. Dronskowski
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Electronic band gap reduction in manganese carbodiimide: MnNCN. J. Phys. Chem. C.
T. K. Boyko, R. J. Green, R. Dronskowski, A. Moewes
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The magnetic structure of Co(NCNH)2 as determined by (spin-polarized) neutron diffraction. J. Solid State Chem. 2013, 202, 149–153
P. Jacobs, A. Houben, A. Senyshyn, P. Müller, R. Dronskowski
