X‐Ray K‐Absorption Study of Copper in Malachite Mineral

Abstract

The shape and chemical shift of the Cu K-absorption edge in malachite mineral are studied by using a Cauchois type bent crystal X-ray spectrograph. The oxidation state of copper is established as two in the mineral. The peaks A, B, and C observed in the absorption edge are explained on the basis of molecular orbital theory (MOT).Die Form und chemische Verschiebung der Cu-K-Absorptionskante im Malachitmineral wird mit einem Rontgenspektrograph nach Cauchois mit gebogenem Kristall untersucht. Der Oxidationszustand von Kupfer wird fur das Mineral zu zwei bestimmt. Die Maxima A, B und C, die an der Absorptionskante beobachtet werden, werden auf der Grundlage der Molekulbahntheorie (MOT) erklart.

Chemically oscillating reactions in the formation of botryoidal malachite

“…In the Katanga malachite, most of these compounds occur (Table 2) and it is possible they could have contributed to chemical oscillations. The oxidation state of Cu in malachite is well-established to be +2 and Cu is a metal that can be halogenated by Br and I (Hemachandran and Chetal, 1986). Hence, since both Br and I occur in ppm levels in the Katanga malachite, a possible scenario could also involve Cu +1 and Cu 0 during diagenetic and supergene conditions, which could potentially contribute to the abiotic…”

EXAFS Studies of Some Copper(II) Mixed-Ligand Complexes

“…1. The compounds studied earlier [6] A perusal of Table 1 and this sequence of variation of chemical shifts indicate that in all the four complexes with glutamic acid as primary ligand the values are respectively higher as compared to the corresponding complex with aspartic acid as the primary ligand. For example, for water as secondary ligand the values are 7.5 and 5.8 eV, respectively; for pyridine the values are 6.4 and 5.4 eV, respectively; for imidazole the values are 6.8 and 5.2 eV, respectively and similarly for benz-imidazole, the values are 5.7 and 4.5 eV, respectively.…”

“…For example, for water as secondary ligand the values are 7.5 and 5.8 eV, respectively; for pyridine the values are 6.4 and 5.4 eV, respectively; for imidazole the values are 6.8 and 5.2 eV, respectively and similarly for benz-imidazole, the values are 5.7 and 4.5 eV, respectively. Hence, on this basis, we infer that the glutamic acid complexes are more ionic [6,7] as compared to their corresponding aspartic acid complexes having similar secondary ligands. As far as the four complexes are concerned having the same primary ligand, either glutamic acid or aspartic acid, but different secondary ligand the trend shows that the chemical shifts vary as follows: For the explanation of this we give the spectrochemical series below: .…”

Chemical Shift of X-Ray K-Absorption Edge of Ni in Some of its Compounds and its Correlation with Partial Charge

“…the chemical shift, ΔE, (in eV) is given by where ECompound = energy (in eV) of the absorption edge in a compound and E M e t a l = e n e r g y o f t h e a b s o r p t i o n e d g e i n a p u r e m e t a l . T h e c h e m i c a l s h i f t d e p e n d s upon various factors [1][2][3][4][5][6] such as effective charge, valency, nature of ligands, coordination number, etc.…”