Table 1.

Bond lengths in Å, k${}^a$ in mDyn/Å, BSO and H(r${}_b$), in Hartree/Å${}^3$, spin multiplicity and oxidation number of uranium for N≡U≡N, U≡N, N≡U=NH, N≡U=O and UO${}_2$${}^{\left(a\right)}$ calculated at the NESCau/PBE0//cc-pwCVTZ-X2C (uranium) and NESCau/PBE0//cc-pVTZ (N,O,H) level of theory.

	U≡N				U=L; L=N,O				U State
	r	k ${}^a$	BSO	H(r${}_{\mathit{b}}$)	r	k ${}^a$	BSO	H(r${}_{\mathit{b}}$)
N≡U≡N	1.713	8.085	3.081	−0.437	-	-	-	-	${}^1{\Sigma }_g$—U(VI)
N≡U	1.732	7.772	2.976	−0.398	-	-	-	-	${}^4\Sigma$—U(III)
N≡U=NH	1.695	8.077	3.078	−0.474	1.828	4.918	1.989	−0.222	${}^2\Delta$—U(V)
N≡U=O	1.697	8.554	3.238	−0.470	1.761	7.824	2.066	−0.319	${}^2\Phi$—U(V)
UO${}_2$	-	-	-	-	1.836	5.883	1.689	−0.239	${}^1{\Phi }_u$—U(IV)
UO${}_2$	-	-	-	-	1.775	7.288	1.966	−0.310	${}^3{\Phi }_u$—U(IV)

^(a)${}^3{\Phi }_u$ is the ground state of UO₂ being 40.0 kcal·mol⁻¹ more stable than the singlet ${}^1{\Phi }_u$ state.