Bourakhouadar Hicham, Hempelmann Jan, van Leusen Jan, Drichel Andreas, Bayarjargal Lkhamsuren, Koldemir Aylin, Reimann Maximilian Kai, Pöttgen Rainer, Slabon Adam, Corkett Alex J, Dronskowski Richard
Chair of Solid-State and Quantum Chemistry, Institute of Inorganic Chemistry, RWTH Aachen University, 52056 Aachen, Germany.
Institute of Innovative Research, Tokyo Institute of Technology, Yokohama 226-8503, Japan.
J Am Chem Soc. 2024 Sep 25;146(38):26071-26080. doi: 10.1021/jacs.4c06162. Epub 2024 Sep 16.
Two novel ternary air-stable transition-metal carbodiimides, MnHf(NCN) and FeHf(NCN), were synthesized via solid-state metathesis using either ZnNCN or NaNCN as the carbodiimide source and the corresponding binary metal chlorides. These two phases are the first examples of transition-metal carbodiimides with an (NCN) composition, akin to ubiquitous O perovskite oxides. The crystal structure of MnHf(NCN) was determined and refined from powder X-ray diffraction (XRD) data in the non-centrosymmetric space group 622 allowing for chirality, the assignment of which is supported by second-harmonic generation (SHG) measurements. FeHf(NCN) was found to crystallize isotypically, and the presence of iron(II) in a high spin state was confirmed by Fe Mößbauer spectroscopy. The structures are revealed to be NiAs-derived and can be described as a hexagonal stack of NCN anions with metal cations occupying 2/3 of the octahedral voids. Both IR spectroscopic measurements and DFT calculations agree that the NCN unit is a bent carbodiimide with symmetry, necessary to account for the size difference present in such a vacancy-ordered structure. Magnetic studies reveal predominantly strong antiferromagnetic interactions but no long-range order between the paramagnetic Mn centers, likely due to the dilution of Mn over the octahedral sites or perhaps even due to some degree of magnetic frustration. The optical and electrochemical properties of MnHf(NCN) were then studied, revealing a wide band gap of 3.04 eV and p-type behavior.
通过固态复分解反应，以ZnNCN或NaNCN作为碳二亚胺源以及相应的二元金属氯化物，合成了两种新型的三元空气稳定的过渡金属碳二亚胺MnHf(NCN)和FeHf(NCN)。这两个相是具有(NCN)组成的过渡金属碳二亚胺的首个实例，类似于普遍存在的氧钙钛矿氧化物。通过粉末X射线衍射（XRD）数据在允许手性的非中心对称空间群622中确定并精修了MnHf(NCN)的晶体结构，二次谐波产生（SHG）测量支持了其手性的归属。发现FeHf(NCN)以同型方式结晶，Fe穆斯堡尔光谱证实了高自旋态铁(II)的存在。结构显示为衍生自NiAs型，可描述为NCN阴离子的六方堆叠，金属阳离子占据八面体空隙的2/3。红外光谱测量和密度泛函理论（DFT）计算均表明，NCN单元是具有对称性的弯曲碳二亚胺，这对于解释这种空位有序结构中存在的尺寸差异是必要的。磁性研究表明主要存在强反铁磁相互作用，但顺磁性Mn中心之间不存在长程有序，这可能是由于Mn在八面体位点上的稀释，甚至可能是由于某种程度的磁阻挫。随后研究了MnHf(NCN)的光学和电化学性质，揭示其具有3.04 eV的宽带隙和p型行为。
