Skip to main content

ESRF beamlines uncover new class of carbon-nitrogen anions


Three ESRF beamlines, ID27, ID15B and ID12, have probed the first compounds containing a new “guanidinate” anion. This anion, synthesised in laser-heated diamond anvil cells, expands the family of carbon-nitrogen inorganic anions, and holds promise for optical technologies.

  • Share

Inorganic ternary metal-C-N compounds with covalently bonded C-N anions are a significant class of solids with diverse applications. Among these compounds, cyanides (CN-) and carbodiimides (CN22-) are extensively studied and used in various fields. While these are well-known, the next member of the series – the CN35- anion, a completely deprotonated guanidine molecule – has remained elusive, despite numerous attempts to synthesise it using strong bases to deprotonate guanidine molecules. So far, only partially deprotonated guanidine has been successfully stabilised.

In a recent breakthrough, research teams from the University of Bayreuth, the University of Cologne and Goethe University Frankfurt in Germany have successfully synthesised the first representatives of the guanidinates (SbCN3) and oxo-guanidinates (a series of Ln3O2(CN3) compounds, where Ln = La, Eu, Gd, Tb, Ho, and Yb). These compounds contain [CN3]5- anions, which are analogous to the well-known carbonate anions [CO3]2- but with each oxygen atom replaced by a nitrogen atom. The researchers successfully stabilised the CN35- guanidinate anion in the compounds via solid-state synthesis under extreme conditions in laser-heated diamond anvil cells.

Utilising laser-heated diamond anvil cells, the researchers subjected the samples to extreme conditions of high pressure (up to half a million atmospheres) and high temperature (up to three thousand degrees Celsius). Several synthetic pathways worked. SbCN3 could be synthesised from its constituent elements – antimony (Sb) and nitrogen (N2) – by loading them into a diamond anvil cell, and diamond itself providing the carbon source; alternatively, cyanuric triazide, C3N12, could be the source of both the carbon and nitrogen. Similarly, Ln3O2(CN3) could be synthesised either from its constituent elements or from azides, such as Eu(N3)2 or Yb(N3)2.


Fig. 1.jpg

Fig. 1: Crystal structures of La3O2(CN3) and SbCN3.

Upon successfully synthesising the compounds, the researchers employed the ESRF beamlines ID27 and ID15B to conduct pressure-dependent single-crystal X-ray diffraction to elucidate their crystal structures and properties (Figure 1). Remarkably, SbCN3 crystallises in a simple calcite (CaCO3) structure type, demonstrating a direct analogy to well-known carbonates. Ln3O2(CN3) possess more complex structures and do not have direct structural analogues. The researchers also performed experiments at two other synchrotrons, Petra III in Hamburg, Germany, and the Advanced Photon Source (APS) in Chicago, USA. Additionally, they used X-ray absorption near-edge structure (XANES) spectroscopy at the ESRF’s ID12 beamline to determine the oxidation state of La, +3, which is in excellent agreement with the crystal chemical analysis.

Despite their high-pressure synthesis, the compounds remained stable at ambient conditions, which offers potential for further upscaling and applications. One of the seven discovered novel compounds, SbCN3, exhibits direct band-gap semiconductor properties, making it a promising candidate for optical devices. Furthermore, this novel synthesis approach paves the way for the development of other guanidinates and ortho-nitridocarbonates with promising properties, such as enhanced photochemical water-splitting and non-linear optical devices. The discovery of this new C-N anion could even hold implications for planetary science, as compounds containing such an anion may exist within the interiors of exoplanets.

Principal publications and authors
Stabilization of the CN35- anion in recoverable high-pressure Ln3O2(CN3) (Ln = La, Eu, Gd, Tb, Ho, Yb) oxoguanidinates, A. Aslandukov (a), P.L. Jurzick (b), M. Bykov (b,c), A. Aslandukova (a), A. Chanyshev (a), D. Laniel (d), Y. Yin (a), F.I. Akbar (a), S. Khandarkhaeva (a), T. Fedotenko (d), K. Glazirin (d), S. Chariton (e), V. Prakapenka (e), F. Wilhelm (f), A. Rogalev (f), D. Comboni (f), M. Hanfland (f), N. Dubrovinskaia (a), L. Dubrovinsky (a), Angew. Chem. Int. Ed. 62, 47, e202311516 (2023);

Stabilization of Guanidinate Anions [CN3]5- in Calcite-Type SbCN3, L. Brüning (b), N. Jena (g), E. Bykova (c), P.L. Jurzick (b), N.T. Flosbach (b), M. Mezouar (f), M. Hanfland (f), N. Giordano (d), T. Fedotenko (d), B. Winkler (c), I.A. Abrikosov (g), M. Bykov (b,c), Angew. Chem. Int. Ed. 62, 47, e202311519 (2023);

(a) University of Bayreuth, Bayreuth (Germany)
(b) University of Cologne, Cologne (Germany)
(c) Goethe University Frankfurt, Frankfurt (Germany)
(d) DESY, Hamburg (Germany)
(e) University of Chicago, Chicago, Germany
(f) ESRF
(g) Linköping University, Linköping (Sweden)


About the beamlines
The recently upgraded beamline ID27 addresses some of the most exciting and challenging questions in science at extremely high pressures and temperatures, such as exploring the conditions deep inside planets, searching for room-temperature superconductivity, and synthesizing new super-hard materials. The beamline accommodates s sample environments such as the double-sided laser-heating system, the Paris-Edinburgh press, the nano-stage and the high-pressure helium cryostat. With a much higher photon flux and smaller beam sizes than its predecessor (300×300 nm2), as well as better detector systems, it enables a new class of ultra-high-pressure experiments (P> 4 Matm), time-resolved experiments with millisecond resolution, 2D micro-fluorescence mapping and in-situ X-ray imaging.
Beamline ID15B is dedicated to the determination of the structural properties of solids at high pressure using angle-dispersive diffraction with diamond anvil cells. The beamline operates at a working energy of 30 keV for high-pressure experiments with a flux of 1012 photons/s at 200 mA. The beam size on the sample is typically 5x5 µm2 but can be narrowed down to 1x1 µm2 for megabar pressure experiments. The station is equipped with a variety of sample environments, including several membrane-type diamond anvil cells (0-100 GPa), a liquid He-cooled cryostat to perform high-pressure experiments at low temperatures (down to 10 K) and external resistive heating equipment for high temperatures up to 600 K. Additionally, an external Nd-YAG laser system is available for annealing samples at high-temperatures within the diamond anvil cell.
Beamline ID12 is dedicated to polarisation-dependent X-ray spectroscopy in the tender and hard X-ray range (2 -15 keV). The main research activities are focused on the studies of the electronic and magnetic properties of a wide range of systems, from the bulk permanent magnet to paramagnetic monolayers on surfaces in an element- and orbital-selective manner. A large variety of dichroic experiments sensitive either to magnetism, chirality or both can be performed under multiple extreme conditions of magnetic field (up to 17 Tesla), temperature (up to 800 K, down to 2 K) and pressure (up to 60 GPa). The extreme stability of the optics, together with a highly efficient detection system, allows to reliably measure the dichroic signals with unprecedented signal-to-noise ratio.