Spectrophotometric determination of trace amounts of copper(II) using the homolysis reaction of the copper(II)–N-p-nitrobenzyl-5,10,15,20-tetrakis(4-sulphonatophenyl)porphine complex

Abstract

N-p-N itro benzyI-5,10,15,20-tetra kis(4-su Ip honatop henyl)porp hine[p-N02Bz( Htpps)4-] was synthesized and used for the spectrophotometric determination of trace amounts of copper(ii) based on the following reaction: p-N02Bz(Htpps)4-+ Cull --+ p-N02Bz[Cu(tpps)]3-+ H+ -% Cu(tpps)4-+ pN02BzOH. The p-nitrobenzyl group was removed to produce the non-substituted porphyrins by cleavage of the C-N bond (homolysis reaction). The reaction caused a large change in the absorption spectra and was specific for copper(ii) as this ion fitted well into the porphyrin core. Excess of zinc(ii) and palladium(ti) did not show the homolysis reaction. The acid dissociation constants of the porphyrin (-log K,) were found to be 2.51 k 0.02 and 7.70 k 0.02 at 25 "C and an ionic strength of 0.1 mol dm-3 (NaN03). Optimum conditions for the determination of copper(ii) were investigated and the method was applied to the determination of ppb levels of total copper(ii) in a river water sample and in some interstitial sea-water samples from the mud at the bottom of the Ariake Sea. The molar absorptivity was 4.22 x 105 dm3 mol-1 cm-1 and the Sandell sensitivity was 0.15 ng cm-2 of copper(ii).

HMTA-assisted One-pot Synthesis of Greigite Nano-platelet and Its Magnetic Properties

“…(4), when the C-N bond breaks, the N atom grabs an electron from the 3d orbital of ferrous ion and combine with a proton to form new N-H bonds, resulting in the formation of ferric ion [27] , The ligand structure between Fe 2+ and HMTA accelerate the homolytic cleavage of the C-N bonds [28] and make the decomposition of HMTA even happen at room temperature. The newly formed Fe 3+ further evolves into other species such as Fe(OH)3 and its decomposed product Fe2O3,…”

Determination of trace amounts of Cu(II) in drinking and wastewater samples by a novel catalytic kinetic spectrophotometric method

“…The analytical potential of catalytic kinetic methods, especially for environmental and industrial trace analysis, has progressed recently [12][13][14][15][16][17][18][19]. Several spectrophotometric methods are mainly based on the formation of complexes with Cu(II), which can meet the requirement of sensitivity for the determination of copper in various samples, has been reported but they do not possess sufficient selectivity [14,20,21]. Very recently a survey of various methods developed for Cu(II) determination has been presented by Prasad and Halafihi [12].…”

Kinetics and mechanism of the acid–base reaction of the diacid salts of porphyrin with pyridine in chloroform

“…1,2 The acid dissociation process of diprotonated porphyrins occurs stepwise and the difference between the deprotonation constants is very small for planar porphyrins [pK a1 = 4.76, pK a2 = 4.99 for 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (H 2 tpps 4Ϫ ) in aqueous solution], 3 while the difference is very large for deformed porphyrins substituted in the peripheral position [pK a1 = 2.51, pK a2 = 7.70 for N-nitrobenzyl-5,10, 15,20-tetrakis(4-sulfonatophenyl)porphyrin (p-NO 2 tpps 4Ϫ )]. 4 Karaman and Bruice reported an unusual acid-base equilibrium between protonated 5,10,15,20-tetraphenylporphyrin [(H 4 tpp) 2ϩ ] and Brønsted base solvents like dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF). 5 The diprotonated porphyrin released protons in chloroform in the presence of DMSO and DMF, but the pyridinium ion did not, though the pK a values of diprotonated porphyrin (e.g.…”