The reactions of four new unsymmetrical N,O-donor ligands, {H2BBPETEN= [N-(2-hydroxybenzyl) - N,N' - bis(2 methylpyridyl) -N'-(hydroxyethyl) ethylenodiamine], H3BPETEN=[N,N'- bis(2-hydroxybenzyl) -N- (2-methylpyridyl) -N'- (hydroxyethyl) ethylenodiamine], HTPETEN=[N,N,N'- tris(2-methylpyridyl) -N'- (hydroxyethyl) ethylenodiamine] and H3BIMETEN=[N,N'-(2-hydroxybenzyl)-N-(1-methylimidazol-2-il-methyl)-N'- (hydroxyethyl)ethylenodiamine]}, with Cu(II) salts afforded the following mononuclear compounds: [CuII(HBBPETEN)]ClO4, [CuII(H2BPETEN)]ClO4 , [CuII(HTPETEN)](PF6)2 and [CuII(H2BIMETEN)]ClO4 . All were characterized by EPR, electronic spectroscopy and electrochemistry. The four copper (II) compounds showed interesting electrochemistry properties. All presented an anodic wave that can be attributed to the Cu (I) oxide formation at the electrode surface, or to a Cu0 sediment at the same surface or yet, to Cu(I) -> Cu(II) oxidation process with coupled chemistry reaction, due to their irreversibility. Two of the complexes are described as interesting synthetic models for the active site of the metalloenzyme galactose oxidase.

As constantes de estabilidade e parâmetros isotrópicos de EPR (Ao e g o) foram obtidos por titulações potenciométricas e espectroscopia de EPR, empregando-se soluções aquosas, 15% v/v etanol, de compostos modelo de ácido húmico - ácido salicílico (SALA) - e do artefato de laboratório, ácido nitrohúmico - ácidos 3-nitrossalicílico (3-NSA), 5-nitrossalicílico (5-NSA) e 3,5-dinitrossalicílico - e cátions oxovanádio. Espectros de EPR foram obtidos de soluções dos compostos modelo e o íon VO2+ (V(IV), e as constantes de estabilidade foram obtidas com solução de VO3+ (V(V), sendo que os valores obtidos são 12.77 ± 0.04 até 7.06 ± 0.05 para as espécies ML, e 9.90 ± 0.04 até 4.06 ± 0.05 para as espécies ML2 , de acordo com a diminuição na acidez dos grupos carboxílico e fenólico com a introdução dos substituintes nitro- no anel aromático dos compostos modelo estudados. Os parâmetros de EPR demonstraram que os valores de g o aumentam e os valores de Ao diminuem concomitante ao aumento dos logaritmos das constantes de formação globais encontrados para os complexos.

The stability constants and the isotropic EPR parameters Ao (hyperfine splitting constant) and g o (g value) were obtained by potentiometric titrations and EPR spectroscopy, respectively, of 85%v/v aqueous solutions of model compounds of humic acids - salicylic acid (SALA) - and both nitrohumic acids, a laboratory artifact - nitrosalicylic acids, 3-nitrosalicylic acid (3-NSA), 5-nitrosalicylic acid (5-NSA) and 3,5-dinitrosalicylic acid (3,5-DNSA) and oxovanadium cations. It was possible to record EPR spectra of those model compounds and the ion VO2+ (V(IV)), and the stability constants were obtained from a solution of VO3+ (V(V)), the values for the logarithms of the stability constants ranging from 12.77 ± 0.04 to 7.06 ± 0.05 for the species ML, and from 9.90 ±0.04 to 4.06 ± 0.05 for the species ML2 according to the decrease in the acidity of the carboxylic and the hydroxyl groups in the aromatic ring of the model compounds studied as the -NO2 substituents were added. Species distribution diagrams were also obtained for the equilibria studied. The EPR parameters showed that as the logarithm of the overall stability constants increase, g o values also increase, while Ao values show a tendency to decrease.

A necessidade de se estudar compostos modelo é a de se compreender como os sítios de quelação de substâncias orgânicas complexas como os ácidos húmicos e nitro-húmicos atuam frente a um íon metálico, pois as substâncias húmicas são potenciais fertilizantes orgânicos. As propriedades químicas principais dos complexos encontrados entre os ácidos 3-nitroftálico e 4-nitroftálico e os íons metálicos Fe(III) e Zn(II) foram estudadas por titulações potenciométricas, espectroscopia ultravioleta-visível e voltametria cíclica, e uma titulação potenciométrica experimental foi feita com uma mistura de modelos de ácidos nitro-húmicos e Cu(II). Calculou-se as constantes de equilíbrio para os sistemas, cujas espécies foram detectadas pelas outras técnicas empregadas. Estudos comparativos entre sítios de quelação derivados de nitrossalicilatos e nitrocatecolatos com Fe(III), Zn(II) e Cu(II) são apresentados. Neste trabalho, os ácidos nitro-húmicos, além de possuírem maior teor de nitrogênio que os ácidos húmicos, também exibiram a vantagem de que alguns centros de quelação, preferencialmente, se ligam a íons metálicos nos valores de p[H] próximos aos valores normais do solo, 7,0 a 7,5.

The study of model compounds is necessary in order to obtain information about complex organic substances as in the case of humic substances (HS). These substances are potential organic fertilizers and have other important functions in soils, natural waters and organic sediments. The main chemical properties of the complexes formed from 3-nitrophthalic and 4-nitrophthalic acids and the metal ions Fe(III) and Zn(II) were studied using potentiometric titrations, ultraviolet-visible spectroscopy (UV-Vis) and cyclic voltammetry (CV). A trial potentiometric titration was done with a mixture of the models for nitrohumic acids and Cu(II). Equilibrium constants for the systems were calculated and UV-Vis and CV were employed to monitor the formation of the species. Comparative studies involving chelating centres of nitrosalicylic acids and nitrocatechols with Fe(III), Zn(II) and Cu(II) are presented. The initial studies involving the nitrohumic substances (NHS), a laboratory artifact of HS have been made and good evidence was found for the further use of NHS as a potential organic fertilizer as well as HS. In this present work one of the observed advantages of NHS over HS was that some aromatic nitro- centres can bind some metal ions at p[H] values of normal soils, near 7.0 to 7.5.