Two novel Ru(II)-Rh(III) polypyridine dyads, containing carboxylic functions at the Rh(III) unit, Rh III (dcb) 2 -(BL)-Ru II (dmp) 2 and Rh III (dcb) 2 -(BL)-Ru II (bpy) 2 (bpy ) 2,2′-bipyridine; dcb ) 4,4′-dicarboxy-2,2′-bipyridine; dmp ) 4,7-dimethyl-1,10-phenanthroline; BL ) 1,2-bis[4-(4′-methyl-2,2′-bipyridyl)]ethane), have been synthesized. Their photophysical behavior in solution, compared with that of the mononuclear Ru II (dcb) 2 (dmb) model (dmb ) 4,4′-dimethyl-2,2′-bipyridine), indicates the occurrence of fast (10 8 -10 9 s -1 ) and efficient (>95%) Rh(III)-*Ru(II) f Rh(II)-Ru(III) photoinduced electron transfer. These species adsorb firmly on nanoporous TiO 2 films, via the dcb ligands of the Rh(III) units. The behavior of the adsorbed species has been studied by means of nanosecond time-resolved emission and absorption measurements, as well as by photocurrent measurements. Photocurrent action spectra demonstrate that light absorption by the Ru(II) chromophore leads to electron injection into the semiconductor. A detailed analysis of the transient behavior of the TiO 2 -Rh III (dcb) 2 -(BL)-Ru II (bpy) 2 system indicates that about one-third of the adsorbed dyads (probably because of different orientation at the surface or accidental contacts in small cavities) undergo direct electron injection from the excited state of the Ru(II) chromophore. The remaining dyads display stepwise charge injection processes, i.e., intramolecular electron transfer, TiO 2 -Rh(III)-*Ru(II) f TiO 2 -Rh(II)-Ru(III), followed by charge separation by electron injection,TiO 2 -Rh(II)-Ru(III) f TiO 2 (e -)-Rh(III)-Ru(III). The first process has comparable rates and efficiencies as for the free dyads in solution. The second step is 40% efficient, because of competing primary recombination, TiO 2 -Rh(II)-Ru(III) f TiO 2 -Rh(III)-Ru(II). When the final recombination between injected electrons and oxidized Ru(III) centers is studied, a remarkable slowing down is obtained for the supramolecular systems, e.g., TiO 2 -Rh III (dcb) 2 -(BL)-Ru II (bpy) 2 , relative to analogous systems containing simple mononuclear sensitizers, e.g., TiO 2 -Ru II (dcb) 2 (dmb). Stepwise charge separation and slow recombination between remote sites are distinctive features that suggest the labeling of these systems as "heterotriads".

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Resumo -A tecnologia de aplicação de fitossanitários visa à colocação uniforme do produto no alvo, com mínimas perdas para o solo e por deriva. Desta forma, os objetivos deste trabalho foram estudar a deposição do herbicida 2,4-D Amina, aplicado em diferentes condições operacionais, em plantas infestantes e comparar as metodologias de estudo de deposição baseadas na detecção do ingrediente ativo por cromatografia líquida de alta eficiência (HPLC) e de um traçador adicionado à calda por espectrofotometria. O experimento foi conduzido em delineamento de blocos casualizados, com seis tratamentos e quatro repetições, dispostos em esquema fatorial 3 x 2: três pontas de pulverização (ponta de jato plano duplo de pré-orifício, ponta de jato plano defletor e ponta de jato plano defletor com indução de ar) e dois volumes de aplicação (80 e 130 L ha -1 ). Foi realizado o estudo de deposição de calda nas plantas infestantes, perdas para o solo e perdas por exoderiva. Concluiu-se que houve baixa correlação entre os dados de deposição na folhagem das plantas infestantes obtidos com as duas metodologias. Pontas que produzem gotas grossas podem ser utilizadas na dessecação, sem comprometer a cobertura do alvo. Quanto à deposição junto ao solo, a correlação foi significativa. Pontas de jato plano defletor com indução de ar promoveram maior perda de herbicida para o solo. Não foi possível detectar perdas por exoderiva pelas metodologias empregadas.Palavras-chave -Pesticidas -Aplicação. Defensivos vegetais. Equipamentos de pulverização. Pesticidas.Abstract -Pesticide spray technology aims the uniform deposition of products in the target, with minimal losses to the soil or drift. Thus, the objectives of this study were to evaluate the 2,4-D Amine deposition, applied on weeds in different operational conditions, and compare two different measurement techniques: analysis of 2,4-D by high performance liquid chromatography and tracer analysis using spectrophotometry. The experimental design was randomized blocks with six treatments and four replications, as a 3 x 2 factorial model: three spray nozzles (drift guard twin flat-fan, turbo flat-fan and air induction turbo flatfan) and two spray volumes (80 L ha -1 and 130 L ha -1 ). The spray process was studied by the deposition on the weeds, losses to the soil, and losses by exo-drift. According to the results, it can be concluded that the correlation coefficient between the results of weed deposition from the two methodologies was low. Coarse droplets can be used for weed desiccation, without compromising target coverage. The correlation was significant to the soil loss. Air induction turbo flat-fan nozzles promoted greater herbicide loss to the soil. Drift was not detected with the methodologies employed.

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