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A series of isostructural Ln(3)O(2)(CN3) (Ln=La, Eu, Gd, Tb, Ho, Yb) oxoguanidinates was synthesized under high-pressure (25-54 GPa) high-temperature (2000-3000 K) conditions in laser-heated diamond anvil cells. The crystal structure of this novel class of compounds was determined via synchrotron single-crystal X-ray diffraction (SCXRD) as well as corroborated by X-ray absorption near edge structure (XANES) measurements and density functional theory (DFT) calculations. The Ln(3)O(2)(CN3) solids are composed of the hitherto unknown CN35- guanidinate anion-deprotonated guanidine. Changes in unit cell volumes and compressibility of Ln(3)O(2)(CN3) (Ln=La, Eu, Gd, Tb, Ho, Yb) compounds are found to be dictated by the lanthanide contraction phenomenon. Decompression experiments show that Ln(3)O(2)(CN3) compounds are recoverable to ambient conditions. The stabilization of the CN35- guanidinate anion at ambient conditions provides new opportunities in inorganic and organic synthetic chemistry., Funding Agencies|National Science Foundation; DOE Office of Science by Argonne National Laboratory; UKRI Future Leaders Fellowship; Deutsche Forschungsgemeinschaft (DFG) [DE-AC02-06CH11357, MR/V025724/1, 2009 00971]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University; Projekt DEAL; [DU 954-11/1]; [DU 393-9/2]; [DU 393-13/1]; [DU 945/15-1]; [EAR- 1634415]

The stabilization of nitrogen-rich phases presents a significant chemical challenge due to the inherent stability of the dinitrogen molecule. This stabilization can be achieved by utilizing strong covalent bonds in complex anions with carbon, such as cyanide CN- and NCN(2- )carbodiimide, while more nitrogen-rich carbonitrides are hitherto unknown. Following a rational chemical design approach, we synthesized antimony guanidinate SbCN3 at pressures of 32-38 GPa using various synthetic routes in laser-heated diamond anvil cells. SbCN3, which is isostructural to calcite CaCO3, can be recovered under ambient conditions. Its structure contains the previously elusive guanidinate anion [CN3](5-), marking a fundamental milestone in carbonitride chemistry. The crystal structure of SbCN3 was solved and refined from synchrotron single-crystal X-ray diffraction data and was fully corroborated by theoretical calculations, which also predict that SbCN3 has a direct band gap with the value of 2.20 eV. This study opens a straightforward route to the entire new family of inorganic nitridocarbonates., Funding Agencies|Deutsche Forschungsgemeinschaft (DFG Emmy-Noether Program) [BY112/2-1]; Deutsche Forschungsgemeinschaft (DFG Emmy-Noether project) [BY 101/2-1]; Knut and Alice Wallenberg Foundation (Wallenberg Scholar grant) [KAW-2018.0194]; Swedish Research Council (VR) grant [2019-05600]; Swedish Government Strategic Research Areas in Materials Science on Functional Materials at Linkoeping University (Faculty Grant SFO-Mat-LiU) [2009 00971]; Swedish Research Council [2022-06725]; Biovia Science ambassador program; Projekt DEAL

A series of isostructural Ln(3)O(2)(CN3) (Ln=La, Eu, Gd, Tb, Ho, Yb) oxoguanidinates was synthesized under high-pressure (25-54 GPa) high-temperature (2000-3000 K) conditions in laser-heated diamond anvil cells. The crystal structure of this novel class of compounds was determined via synchrotron single-crystal X-ray diffraction (SCXRD) as well as corroborated by X-ray absorption near edge structure (XANES) measurements and density functional theory (DFT) calculations. The Ln(3)O(2)(CN3) solids are composed of the hitherto unknown CN35- guanidinate anion-deprotonated guanidine. Changes in unit cell volumes and compressibility of Ln(3)O(2)(CN3) (Ln=La, Eu, Gd, Tb, Ho, Yb) compounds are found to be dictated by the lanthanide contraction phenomenon. Decompression experiments show that Ln(3)O(2)(CN3) compounds are recoverable to ambient conditions. The stabilization of the CN35- guanidinate anion at ambient conditions provides new opportunities in inorganic and organic synthetic chemistry., Funding Agencies|National Science Foundation; DOE Office of Science by Argonne National Laboratory; UKRI Future Leaders Fellowship; Deutsche Forschungsgemeinschaft (DFG) [DE-AC02-06CH11357, MR/V025724/1, 2009 00971]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University; Projekt DEAL; [DU 954-11/1]; [DU 393-9/2]; [DU 393-13/1]; [DU 945/15-1]; [EAR- 1634415]

The stabilization of nitrogen-rich phases presents a significant chemical challenge due to the inherent stability of the dinitrogen molecule. This stabilization can be achieved by utilizing strong covalent bonds in complex anions with carbon, such as cyanide CN- and NCN(2- )carbodiimide, while more nitrogen-rich carbonitrides are hitherto unknown. Following a rational chemical design approach, we synthesized antimony guanidinate SbCN3 at pressures of 32-38 GPa using various synthetic routes in laser-heated diamond anvil cells. SbCN3, which is isostructural to calcite CaCO3, can be recovered under ambient conditions. Its structure contains the previously elusive guanidinate anion [CN3](5-), marking a fundamental milestone in carbonitride chemistry. The crystal structure of SbCN3 was solved and refined from synchrotron single-crystal X-ray diffraction data and was fully corroborated by theoretical calculations, which also predict that SbCN3 has a direct band gap with the value of 2.20 eV. This study opens a straightforward route to the entire new family of inorganic nitridocarbonates., Funding Agencies|Deutsche Forschungsgemeinschaft (DFG Emmy-Noether Program) [BY112/2-1]; Deutsche Forschungsgemeinschaft (DFG Emmy-Noether project) [BY 101/2-1]; Knut and Alice Wallenberg Foundation (Wallenberg Scholar grant) [KAW-2018.0194]; Swedish Research Council (VR) grant [2019-05600]; Swedish Government Strategic Research Areas in Materials Science on Functional Materials at Linkoeping University (Faculty Grant SFO-Mat-LiU) [2009 00971]; Swedish Research Council [2022-06725]; Biovia Science ambassador program; Projekt DEAL