Record High Magnetic Anisotropy in Three Coordinate MnIII and CrII Complexes: A Theoretical Perspective

Ab initio calculations performed in two three-coordinate complexes [Mn{N(SiMe 3 ) 2 } 3 ] (1) and [K(18-crown-6)(Et 2 O) 2 ][Cr{N(SiMe 3 ) 2 } 3 ] (2) reveal record-high magnetic anisotropy with the D values -64 cm -1 and -15 cm -1 respectively, enlisting d 4 ion back in the race for single-ion magnets. For the first time, a detailed spin-vibrational analysis was performed in 1 and 2 that suggest a dominant under barrier relaxation due to flexible coordination sphere around the metal ion offering design clues for low coordinate transition metal SIMs.