Spectroscopy of 3 d Complexes

Bonding and ion–ion interactions of Mn2+ ions in fluoride-phosphate and boro-silicate glasses probed by EPR and fluorescence spectroscopy

“…The addition of manganese to glasses leads to the development of absorption bands around 410 and 530 nm, due to d-d electronic transitions of Mn 2+ (d 5 ) and Mn 3+ (d 4 ) ions, respectively [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. All d-d transitions are parity forbidden, but only transitions of the d 5 ion Mn 2+ , and not of the d 4 ion Mn 3+ , are also spin forbidden.…”

“…The energy of the band corresponding to the 6 A 1g (S) → 4 E g (G) and 6 A 1g (S) → 4 A 1g ( 4 G) transitions relies primarily on the reduction of inter-electronic repulsion brought about by an expansion of the 3d orbitals. Therefore, the nephelauxetic effect can be utilized once more in measuring the change in electron density provided by anions in different glasses [1][2][3][4][5][6][7]30]. The 6 S− 4 G energy difference of the complexed Mn 2+ ion in glass (ν S → G ) relative to the frequencies of the free uncomplexed Mn 2+ ion (ν f S → G =26846 cm − 1 ) is related to the orbital expansion effect of the ligands, h or h oxygen , by:…”

“…All d-d transitions are parity forbidden, but only transitions of the d 5 ion Mn 2+ , and not of the d 4 ion Mn 3+ , are also spin forbidden. Accordingly, transitions of Mn 2+ ions have a 100 times lower extinction coefficient and the color of glasses depends mostly on the Mn 3+ content, which cause a dark purple coloring even in low concentrations [1][2][3][4][5][6][7][8][9]13,14]. Analysis of the optical spectra of the Mn x Sr 1−x (PO 3 ) 2 series [14] showed that in glasses prepared under reducing conditions only 0.07 to 0.75% of all Mn-ions were in the trivalent state.…”

“…It is known that manganese is present in glasses as Mn 3+ or Mn 2+ ions; both ions having been extensively studied with regards to their coordination and bonding environment. Optical spectroscopy allows one to distinguish between the different valence states, and by using ligand field theory it is further possible to determine the ion coordination and ligand field splitting parameters in different glasses [1][2][3][4][5][6][7][8][9]14]. Unfortunately, Mn 3+ can easily obscure the transitions of Mn 2+ ions in the optical spectra especially at higher manganese contents.…”

“…Transition metal (TM) ions in glasses often cause characteristic colors and magnetic properties, which in turn makes them prime candidates for studies by optical absorption [1][2][3][4][5][6][7][8][9], fluorescence [1,[7][8][9][10][11][12][13] and electron paramagnetic resonance (EPR) spectroscopy [1,[13][14][15][16][17][18][19][20][21][22][23][24]. Manganese is next to iron one of the most common impurities in glasses and its intentional use as coloring and decoloring agent reaches as far back as to the Egyptian and Roman times [25].…”