High-field EPR investigation of a series of mononuclear Mn(II) complexes doped into Zn(II) hosts

The five-coordinate mono-halide mononuclear Zn(II) complexes [Zn(tpa)X]+ (tpa = tris(2-pyridylmethyl)amine; X = I ([Zn(tpa)I]I; 1a), Br ([Zn(tpa)Br](ZnBr4)0.5; 2a) and Cl ([Zn(tpa)Cl](ZnCl4)0.5; 3a)) and the six-coordinate mononuclear complex [Zn(tpa)(NCS)2] (4a) have been synthesized and characterized by X-ray crystallography. The [Zn(tpa)X]+ complexes doped with the corresponding [Mn(tpa)X2] complexes (X = I (1b), Br (2b) and Cl (3b)) have been synthesized and their electronic properties investigated by multifrequency high field EPR (HF-EPR) (95–285 GHz). The magnetically diluted conditions allow the determination of the hyperfine coupling constant A (∣A∣ = 68.10−4 cm−1 for 1b–3b). The zero-field splitting parameters (D and E) found for 1b–3b are comparable to those found for neat samples of the [Mn(tpa)X2] complexes (1b: ∣D∣ = 0.635 cm−1, ∣E/D∣ = 0.189; 2b: ∣D∣ = 0.360 cm−1, ∣E/D∣ = 0.192; 3b: ∣D∣ = 0.115 cm−1, ∣E/D∣ = 0.200). The efficacy of using multifrequency EPR under dilute conditions to precisely determine spin Hamiltonian parameters is discussed.

Graphical abstractThe mononuclear Zn(II) complexes [Zn(tpa)X]+ (X = I, Br, Cl) and [Zn(tpa)(NCS)2] have been synthesized and characterized by X-ray crystallography. The electronic properties of the [Mn(tpa)X2] (X = I, Br, Cl) complexes doped into the corresponding Zn(II) complexes have been investigated by multifrequency high field EPR (HF-EPR) spectroscopy.Figure optionsDownload full-size imageDownload as PowerPoint slide