Reactions of Cr³⁺ with aspartic acid within a wide pH range

Abstract

Formation of the metal complexes of aspartic acid (Asp) with the chromium metal ion (Cr 3+ ) in solutions using potentiometric titrations is presented within a wide pH range (∼3.5 to ∼10.5) at 25 • C and I = 0.10 M NaNO 3 . Concentration distribution diagrams revealed that the main complex formed within this pH range is the bis Cr 3+ complex. Literature stability constant values for the Cr-Asp complexes were used to construct concentration distribution diagrams. Complexes taken into consideration were the simple one-to-one complex, the bis-complex, and the bis-mono-protonated complex, namely, Cr-Asp, Cr(Asp) 2 , and Cr(Asp) 2 H. The corresponding Log β values of these complexes were 12.46, 21.86, and 24.30, respectively. UV-Vis spectra demonstrate Cr 3+ -Asp binding. The UV-Vis spectra were collected from a system that reached a high level of equilibrium state (50 days' equilibrium time).

A2AgCrBr6 (A = K, Rb, Cs) and Cs2AgCrX6(X = Cl, I) Double Perovskites: A Transition-Metal-Based Semiconducting Material Series with Remarkable Optics

“…This is not surprising given that the ground state of the Cr 3+ (t 2g 3 e g 0 ) cation in an octahedral O h symmetry is described by 4 A 2 g ( F ), and is accompanied with spin-allowed transitions from the 4 A 2 g ( F ) ground state to the excited 4 T 2 and 4 T 1 states (that is, 4 T 2 → 4 T 1 and 4 A 2 → 4 T 1 ). Such d–d transitions were reported to occur at energies of 3.06 eV (405 nm) and 2.25 eV (550 nm) in the UV–vis spectrum of isolated Cr 3+ complex of aspartic acid, respectively [ 93 ]. The intense and broad bands observed at energies of 2.93 eV and 2.13 eV for strontium formate dehydrate crystal of Cr 3+ were attributed to the corresponding transitions, respectively [ 94 ].…”

Spectroscopic and Kinetic Study of Sucrose Oxidation by Cr(VI) and Its Application in the Quantitative Analysis of Soil Organic Carbon

“…This is the analyte peak and the absorption band is absent in both the red and blue reference spectra. The Cr(III) ions are known to exhibit an absorption band in the visible region with a lambda maximum value of about 550 nm [16]. Its actual absorption band is partially masked by the absorption band of Cr(VI) that begins at about 570 nm within neighboring range.…”

Aspartic acid in a new role: Synthesis and application of a pH-responsive cyclopolymer containing residues of the amino acid

“…The presence of the amino acid residues in the polymer is thus anticipated to enhance the chelating ligand properties of every repeating unit. The metal ion-binding properties of aspartic acid are well known [12][13][14]. Aspartic acid is known to act as a bidentate (D, E) or a tridentate ligand (F) forming complexes with almost all metal ions via its three binding sites (Scheme 1) [15,16].…”