Polarized charge transfer spectroscopy of Cu²⁺in doped one-dimensional [N(CH₃)₄]CdCl₃and [N(CH₃)₄]CdBr₃crystals

Abstract

This work investigates the polarized charge-transfer (cr) spectra of the Jahn-Teller distorted CuC$ and CUB$ complexes formed in Cu'+-daped m(CH3)4]CdCI3 and [N(CH3)4]CdBr3 crystals. The transition energies as well as the dominant polarization of the cr bands along the hexagonal e direction are explained in terms of rhombic 0% distortions. In the bromide complexes, the strong spin-orbit interaction of the Br-ligands leads to additional bands in the low-temperature spectra Evidence of vibmnic couplings to totally symmetric vibrations is found from analpis of the temperature dependence of the band width.The influence of Cuz+ impurities in the lattice dynamics is studied though the v ~a t i o n undergane by different spectroscopic parmeters in the 10-300 K range. Throughout lhis work. the high sensitivity of cr tnnsitions for detecting the structural phwe bansitions exhibited by these crystals is demonsbated. In particular, the enhancement of the first-order character of the ferroelectric phase Vansition in [N(CHI)I]C~B~~:CU'+ at TF = 157 K which has ken associated with the presence of Cu2+ impurities is worth noting.

Thermochromic properties of the ferroelectric -doped : study of the temperature-induced dichroism

“…(TMA)Hg[Cu]Br 3 is green at room temperature. This colour, which is different to those shown by other Cu 2+ -doped bromide crystals containing either CuBr 2− 4 (purple) [9] or CuBr 4− 6 (red) [8] complexes, is due to the presence of an unusual Br − → Cu 2+ CT band at 15 800 cm −1 . This band appears shifted to lower energy with respect to the first CT transition in CuBr 2− 4 and CuBr 4− 6 (16 800 and 19 300 cm −1 , respectively).…”

“…Due to the low symmetry of the Hg 2+ site, the substitution of Hg 2+ by Cu 2+ in (TMA)HgBr 3 leads to a highly distorted local geometry beyond the usual Jahn-Teller distortion of D 2d (CuBr 2− 4 ) or D 4h (CuBr 4− 6 ) symmetry. This situation gives rise to new features in the CT spectra, not observed previously in Cu-doped systems containing either CuBr 4− 6 or CuBr 2− 4 [8,9].…”

“…In bromides, however, the colour is mainly determined by the intense Br − → Cu 2+ CT bands, since, at variance with chlorides, the CT spectra spread over the whole visible range due to the overall redshift of about 5000-10 000 cm −1 experienced by CT bands of copper complexes when Cl − is replaced by Br − [8,9]. This redshift is in agreement with the 6000 cm −1 predicted from the optical electronegativity difference of these two ligands ( χ = χ(Cl − ) − χ(Br − ) = 0.2) [10].…”

“…In this work, we report polarized CT spectra of (TMA)Hg[Cu]Br 3 and their dependence on temperature. The results are compared with those obtained in orthorhombic (TMA) 2 Hg[Cu]Br 4 and (TMA) 2 Cd[Cu]Br 4 , and in hexagonal (TMA)Cd[Cu]Br 3 and (TMA)Mn[Cu]Br 3 , where the Cu 2+ coordination is CuBr 2− 4 (D 2d symmetry) [9] and CuBr 4− 6 (elongated D 4h symmetry) [8], respectively.…”

Crystal Chemistry, Optic and Magnetic Characterizations of a New Copper Based Material Templated by Hexahydrodiazepine

“…Nowadays, low-dimensional OIHs based on transition metals have been investigated as good alternatives for applications in nonhazardous devices . As a consequence of the Jahn–Teller effect, these materials exhibit efficient absorption in the UV–Vis–NIR region, resulting from the electronic transitions which include both d–d transitions and ligand-to-metal charge transfer (LMCT) . This large absorption makes them suitable for applications in PVs as absorbers. , For example, the reported zero-dimensional compound CH 3 NH 3 FeCl 4 has demonstrated its usefulness as a photodetector and has shown a photoelectric conversion efficiency (PCE) of 0.054% when applied in the FTO/TiO 2 /CH 3 NH 3 FeCl 4 /carbon electrode device (FTO, fluorine-doped tin oxide) .…”