A contaminação do meio ambiente por compostos organoclorados persistentes constitui um problema da sociedade moderna. A geração de resíduos nos laboratórios de ensino e pesquisa também é preocupante. Reagentes como 2,3-dicloro-5,6-diciano-p-benzoquinona (DDQ) e 2,3,5,6-tetracloro-p-benzoquinona (p-cloranil) são bastante utilizados em síntese orgânica, principalmente na síntese de porfirinas onde são empregados em excesso. Essa é uma atividade rotineira no Laboratório de Bioinorgânica onde este trabalho foi desenvolvido, o que tornou necessário o estudo de métodos para o tratamento de resíduos que contenham estes compostos como constituintes principais. Além disso, estes compostos podem ser úteis como moléculas modelo nos estudos de degradação de organoclorados em meio aquoso. Neste trabalho foram estudados dois métodos de degradação para a DDQ e o p-cloranil em meio aquoso: (1) Processo Oxidativo Avançado que utiliza H2O2 e radiação UV e (2) Processo bioinspirado que utilizada ferro(III)tetrassulfoftalocianina (FeIIIPcS) como catalisador e H2O2 como oxidante. Nesse último, FeIIIPcS foi utilizada em meio homogêneo e suportada em sílica funcionalizada com grupos N-trimetoxissililpropil-N,N,N-trimetilamônio. No processo que utiliza H2O2/UV foi utilizado um reator em batelada que possui como fonte de radiação uma lâmpada de vapor de Hg de alta pressão sem o bulbo. Esse processo mostrou-se bastante eficiente na fotodegradação da DDQ e do p-cloranil em meio básico, possibilitando atingir baixos valores de Carbono Orgânico Total (COT). Para uma solução 100 ppm de C preparada a partir da DDQ, foram obtidos 1,6% de COT em 2 h de irradiação, quando foram utilizados 60 mmol L-1 de H2O2. Nessa mesma condição foram obtidos 4,4% de COT em 4 h de irradiação da solução 100 ppm de C preparada a partir do p-cloranil. Ácido cloranílico (solução ácida), principal produto da hidrólise básica do p-cloranil, também foi submetido à fotodegradação utilizando 60 mmol L-1 de H2O2. Partindo-se de uma solução 100 ppm de C de ácido cloranílico obteve-se 0,7% de COT em 1 h de irradiação. O sistema FeIIIPcS/H2O2 possibilitou, em pH ácido, a degradação do produto originado da hidrólise da DDQ (2-ciano-5,6-dicloro-3-hidroxi-1,4-benzoquinona) e do ácido cloranílico em meio aquoso homogêneo. No entanto, ocorreu degradação do catalisador nesse sistema. Isso não ocorreu quando foi utilizado o catalisador suportado. O ácido cloranílico mostrou-se mais resistente à degradação do que a DDQ hidrolisada. Na degradação dessa última, a melhor taxa de conversão foi obtida utilizando a razão molar catalisador:oxidante:substrato igual a 1:500:50, condição na qual a taxa de conversão de substrato foi 79% em 2 h de reação. Nessa condição observou-se, por espectrofotometria UV/Vis, uma degradação mais acentuada do anel quinônico. Este trabalho também apresenta alguns experimentos realizados com o objetivo de melhor compreender o comportamento químico da DDQ, p-cloranil e FeIIIPcS em solução aquosa. / The environmental contamination by persistent organochloride compounds is a problem of modern society. The production of chemical wastes in the teaching and research laboratories is also worrying. Reagents like 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) and 2,3,5,6-tetrachloro-p-benzoquinone (p-chloranil) are frequently used in organic synthesis, mainly in the synthesis of porphyrins where these reagents are employed in excess. This kind of synthesis is frequently performed in the Bioinorganic Laboratory, where this research was developed, and therefore the main objective of this work was to study possible methods to treat chemical wastes containing such compounds as main constituents. Moreover, these compounds can be useful as model molecules in the study of organochlorides degradation in aqueous media. In this work, two degradation methods for DDQ and p-cloranil in aqueous solution were studied: (1) advanced oxidation process using H2O2 and UV radiation and (2) bioinspired process using iron(III)tetrasulfophthalocyanine (FeIIIPcS) as the catalyst and H2O2 as the oxidant. FeIIIPcS was used in a homogeneous system and was supported in functionalized silica containing N-trimetoxisililpropil-N,N,N-trimethylamonium groups. A batch reactor equipped with high-pressure Hg vapor lamp with the bulb removed, as the radiation source, was used in the advanced oxidation processes. These processes revealed to be quite efficient for the photodegradation of DDQ and p-chloranil in alkaline solution, reaching low values of Total Organic Carbon (COT). For a solution containing 100 ppm of C prepared from DDQ and 60 mmol L-1 of H2O2, after 2 hours of irradiation, the COT went down to 1.6%. Under the same conditions, it was obtained 4.4% of COT after 4 hours of irradiation of the solution of 100 ppm of C prepared from p-chloranil. Chloranilic acid (acid solution), the main product obtained from alkaline hydrolysis of p-chloranil, was also submitted to photodegradation using 60 mmol L-1 of H2O2. From a solution of 100 ppm of C of chloranilic acid, 0.7% of COT was obtained after 1 hour of irradiation. The FeIIIPcS/H2O2 system, in acid pH, made possible the degradation of the resulting product of DDQ hydrolysis (2-cyano-5,6-dichloro-3-hydroxy-1,4-benzoquinone) and of chloranilic acid in a aqueous homogeneous solution. However, the degradation of the catalyst occurred in that system. That did not happen when the supported catalyst was used. Chloranilic acid revealed to be more resistant to degradation than hidrolysed DDQ. For the degradation of that one, the best conversion ratio was obtained using the molar ratio catalyst:oxidant:substratum of 1:500:50, condition under which the substratum conversion ratio was 79% after 2 hours of reaction. Under that condition was observed, for UV/Vis spectrophotometry, a more prominent degradation of the quinonic ring. This work also presents some experiments aiming to better understand the DDQ, p-chloranil and FeIIIPcS chemical behavior in aqueous solution.

A contaminação do meio ambiente por compostos organoclorados persistentes constitui um problema da sociedade moderna. A geração de resíduos nos laboratórios de ensino e pesquisa também é preocupante. Reagentes como 2,3-dicloro-5,6-diciano-p-benzoquinona (DDQ) e 2,3,5,6-tetracloro-p-benzoquinona (p-cloranil) são bastante utilizados em síntese orgânica, principalmente na síntese de porfirinas onde são empregados em excesso. Essa é uma atividade rotineira no Laboratório de Bioinorgânica onde este trabalho foi desenvolvido, o que tornou necessário o estudo de métodos para o tratamento de resíduos que contenham estes compostos como constituintes principais. Além disso, estes compostos podem ser úteis como moléculas modelo nos estudos de degradação de organoclorados em meio aquoso. Neste trabalho foram estudados dois métodos de degradação para a DDQ e o p-cloranil em meio aquoso: (1) Processo Oxidativo Avançado que utiliza H2O2 e radiação UV e (2) Processo bioinspirado que utilizada ferro(III)tetrassulfoftalocianina (FeIIIPcS) como catalisador e H2O2 como oxidante. Nesse último, FeIIIPcS foi utilizada em meio homogêneo e suportada em sílica funcionalizada com grupos N-trimetoxissililpropil-N,N,N-trimetilamônio. No processo que utiliza H2O2/UV foi utilizado um reator em batelada que possui como fonte de radiação uma lâmpada de vapor de Hg de alta pressão sem o bulbo. Esse processo mostrou-se bastante eficiente na fotodegradação da DDQ e do p-cloranil em meio básico, possibilitando atingir baixos valores de Carbono Orgânico Total (COT). Para uma solução 100 ppm de C preparada a partir da DDQ, foram obtidos 1,6% de COT em 2 h de irradiação, quando foram utilizados 60 mmol L-1 de H2O2. Nessa mesma condição foram obtidos 4,4% de COT em 4 h de irradiação da solução 100 ppm de C preparada a partir do p-cloranil. Ácido cloranílico (solução ácida), principal produto da hidrólise básica do p-cloranil, também foi submetido à fotodegradação utilizando 60 mmol L-1 de H2O2. Partindo-se de uma solução 100 ppm de C de ácido cloranílico obteve-se 0,7% de COT em 1 h de irradiação. O sistema FeIIIPcS/H2O2 possibilitou, em pH ácido, a degradação do produto originado da hidrólise da DDQ (2-ciano-5,6-dicloro-3-hidroxi-1,4-benzoquinona) e do ácido cloranílico em meio aquoso homogêneo. No entanto, ocorreu degradação do catalisador nesse sistema. Isso não ocorreu quando foi utilizado o catalisador suportado. O ácido cloranílico mostrou-se mais resistente à degradação do que a DDQ hidrolisada. Na degradação dessa última, a melhor taxa de conversão foi obtida utilizando a razão molar catalisador:oxidante:substrato igual a 1:500:50, condição na qual a taxa de conversão de substrato foi 79% em 2 h de reação. Nessa condição observou-se, por espectrofotometria UV/Vis, uma degradação mais acentuada do anel quinônico. Este trabalho também apresenta alguns experimentos realizados com o objetivo de melhor compreender o comportamento químico da DDQ, p-cloranil e FeIIIPcS em solução aquosa. / The environmental contamination by persistent organochloride compounds is a problem of modern society. The production of chemical wastes in the teaching and research laboratories is also worrying. Reagents like 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) and 2,3,5,6-tetrachloro-p-benzoquinone (p-chloranil) are frequently used in organic synthesis, mainly in the synthesis of porphyrins where these reagents are employed in excess. This kind of synthesis is frequently performed in the Bioinorganic Laboratory, where this research was developed, and therefore the main objective of this work was to study possible methods to treat chemical wastes containing such compounds as main constituents. Moreover, these compounds can be useful as model molecules in the study of organochlorides degradation in aqueous media. In this work, two degradation methods for DDQ and p-cloranil in aqueous solution were studied: (1) advanced oxidation process using H2O2 and UV radiation and (2) bioinspired process using iron(III)tetrasulfophthalocyanine (FeIIIPcS) as the catalyst and H2O2 as the oxidant. FeIIIPcS was used in a homogeneous system and was supported in functionalized silica containing N-trimetoxisililpropil-N,N,N-trimethylamonium groups. A batch reactor equipped with high-pressure Hg vapor lamp with the bulb removed, as the radiation source, was used in the advanced oxidation processes. These processes revealed to be quite efficient for the photodegradation of DDQ and p-chloranil in alkaline solution, reaching low values of Total Organic Carbon (COT). For a solution containing 100 ppm of C prepared from DDQ and 60 mmol L-1 of H2O2, after 2 hours of irradiation, the COT went down to 1.6%. Under the same conditions, it was obtained 4.4% of COT after 4 hours of irradiation of the solution of 100 ppm of C prepared from p-chloranil. Chloranilic acid (acid solution), the main product obtained from alkaline hydrolysis of p-chloranil, was also submitted to photodegradation using 60 mmol L-1 of H2O2. From a solution of 100 ppm of C of chloranilic acid, 0.7% of COT was obtained after 1 hour of irradiation. The FeIIIPcS/H2O2 system, in acid pH, made possible the degradation of the resulting product of DDQ hydrolysis (2-cyano-5,6-dichloro-3-hydroxy-1,4-benzoquinone) and of chloranilic acid in a aqueous homogeneous solution. However, the degradation of the catalyst occurred in that system. That did not happen when the supported catalyst was used. Chloranilic acid revealed to be more resistant to degradation than hidrolysed DDQ. For the degradation of that one, the best conversion ratio was obtained using the molar ratio catalyst:oxidant:substratum of 1:500:50, condition under which the substratum conversion ratio was 79% after 2 hours of reaction. Under that condition was observed, for UV/Vis spectrophotometry, a more prominent degradation of the quinonic ring. This work also presents some experiments aiming to better understand the DDQ, p-chloranil and FeIIIPcS chemical behavior in aqueous solution.

Under the electric dipole approximation, second harmonic of the incident light is scattered by a collection of randomly oriented molecular dipoles in solution due to instantaneous orientational fluctuation which is directional. If two such dipoles are correlated in space through intermolecular or other interactions, the intensity of the second harmonic scattered light (SHSL) will be related to the extent of such interactions. If two dipoles are arranged in a particular geometry by design, the geometry will determine the intensity of the SHSL. If a molecule has no dipole moment, the intensity of the SHSL will be less and is only allowed by higher order electric multipoles. If two such zero-dipole molecules interact with each other and transfer some amount of electronic charge from one to the other, the induced dipole moment will give rise to an enhanced SHSL. However, along with the direction of the dipole moment from the donor to the acceptor, the actual geometry of such molecular dimer/complex should also play an important role to determine the nature of the SHSL response. If all the isotropic nonzero components of first hyperpolarizability (β) are taken into account, from the measurement of β and related quantities such as depolarization ratios, in solution it should be possible to derive information about the geometry of the dimer/complex. This is precisely the motivation behind this thesis. Chapter 1 gives a brief introduction of 1:1 charge transfer (CT) complexes between a donor and an acceptor and their importance in chemistry. It also contains an introduction to nonlinear optics, various spectroscopic techniques to characterize CT complexes, etc. The motivation of extracting the geometry of such complexes from hyper-Rayleigh scattering (HRS) measurements in solution is presented in this chapter. In Chapter 2, all the experimental details of the unpolarized and polarization resolved HRS measurements at various excitation wavelengths have been described. Generation of infrared wavelengths (1543 nm and 1907 nm) using stimulated Raman scattering in gases have also been discussed. In Chapter 3, the first hyperpolarizability (βHRS) for two series of 1:1 molecular complexes between methyl substituted benzene donors with tetrachloro-p-benzoquinone (CHL) and dicyanodichloro-p-benzoquinone (DDQ) acceptors in solution at 1543 nm have been presented. Enhancement of βHRS due to charge transfer from the donor to the acceptor molecule which was predicted theoretically has been verified. Using linearly (electric field vector along X direction) and circularly polarized incident light, respectively, two macroscopic depolarization ratios D = I2ω,X,X/I2ω,Z,X and D' = I2ω,X,C/I2ω,Z,C in the laboratory fixed XYZ frame by detecting the SHSL in a polarization resolved fashion have been measured. The experimentally obtained first hyperpolarizability (βHRS), D and D' values, are then matched with the theoretically calculated values from single and double configuration interaction calculations using the Zerner’s intermediate neglect of differential overlap and the self-consistent reaction field (ZINDO–SDCI– SCRF) approach by adjusting the geometrical parameters. It has been found that in most of the CT complexes studied here, there exists a significant twist in the equilibrium geometry at room temperature which is not a simple slipped parallel geometry as was believed. In chapter 4, the βHRS, D and D' values of 1:1 pyridine (PY)-chloranil (CHL) complex at 1064 nm have been described. Previous theoretical studies have shown that there is a tilt angle of 77.9 degree in the gas phase PY-CHL complex. In this chapter, this prediction about the geometry of 1:1 PY-CHL complex has been probed. The experimentally found βHRS, D and D' are matched well with theoretically calculated values, using ZINDO–SDCI–SCRF, for a cofacial geometry of PY-CHL complex in solution indicating that the solution geometry is different from the gas phase geometry. In Chapter 5, the βHRS, D and D' for a series of 1:1 complexes of tropyliumtetrafluoroborate and methyl-substituted benzenes in solution at 1064 nm have been reported. The measured D and D' values vary from 1.36 to 1.46 and 1.62 to 1.72, respectively and are much lower than the values expected from a typical sandwich or a T-shaped geometry. The lowering in D and D' indicates that these complexes have higher symmetry than C2v. The value of D close to 1.5 indicates there is a significant octupolar contribution in such complexes. In order to probe it further, βHRS, D and D' were computed using the ZINDO-SDCI-SCRF technique in the presence of BF4-anion. By arranging the three BF4-ions in a C3 symmetry around the complex in such a way that electrical neutrality is maintained, the computed values are brought to agreement with experiments. This unprecedented influence of the anion on the HRS, D and D' values of these complexes are discussed in this chapter. In Chapter 6, the effect of dipolar interactions, within a multichromophoric system, on the second order nonlinear optical properties have been studied. It has been found that the βHRS response of the multichromophoric system is always larger than expected for uncorrelated chromophores demonstrating that the dipole moment of individual chromophores are not merely additive within the multichromophoric system but contribute cooperatively to the SHSL signal. Also the relative orientation and nature of the chromophores and the angle of interaction between them alter the HRS values. Chapter 7 is the concluding chapter in which all the work done in the thesis has been summarized and future direction has been proposed.