1 2 2-bis(4-pyridyl)ethane 3-triazole 57Fe Mössbauer spectroscopy ?-? interactions C-H···? interactions Cu(II) complexes DFT calculation EPR spectroscopy Fe(II) Fe(II) complex Fe(III) complex Fe(III) coordination complexes LIESST effect SQUID Schiff base UV-Vis spectroscopy X-ray absorption spectroscopy X-ray diffraction [Au(dddt)2]? [Au(dmit)2]? [Fe(III)(3-OMesal2-trien)]+ aminoxyl amorphous atropisomerism charge-transfer phase transition chiral propeller structure cobalt oxide cobalt(II) ion