Abstract The present thesis describes a method for characterization of liquid crystals in confined spaces by means of NMR of probe atoms and molecules. 129Xe isotope enriched xenon gas and 13C isotope enriched methyl iodide and methane were used as probes. Behavior of solutes and liquid crystals confined to porous materials was investigated using 129Xe and 13C NMR spectroscopy. Uniaxial nematic liquid crystals Phase 4 and ZLI 1115 were used as a medium. Controlled pore glass with well defined and known properties was used as a porous material. The behavior of liquid crystals and solutes in various different size pores, temperatures and magnetic fields at different solute concentrations was explained. The average pore diameter of the material varied from mesopores to macropores. The studied temperature range covered solid, nematic and isotropic phases of bulk liquid crystals, and the highest magnetic field was 2.5 times stronger than the lowest one used (4.70 T). The chemical shifts, intensities, and line shapes of the resonance signals from the solutes were observed to contain lots of information about the effect of confinement on the state of the liquid crystals. Especially the line shape of the 13C resonances of methyl iodide was observed to be very sensitive to the liquid crystal orientation distribution in the pores. By varying experimental conditions the relative contribution of field and the surface forces of pore walls to the orientation of liquid crystal molecules inside the pores was seen to change quite drastically. In addition, it was also observed that when the sample is cooled very rapidly, xenon atoms do not squeeze out from the freezing medium but they are occluded inside the solid lattice, and their chemical shift is very sensitive to crystal structure. Furthermore, because solutes experienced on average isotropic environment inside the smallest pores, isotropic value of the shielding tensor could be determined at exactly the same condition and temperature as anisotropic counterpart between the pore particles. Thus, for the first time in the solution state, shielding anisotropies could be determined as a function of temperature.

The thesis presents work regarding amphiphilic molecules associated in aqueous solution or at the liquid/solid interface. Two main topics are included: the temperature-dependent behavior of micelles and the adsorption of dispersants on carbon nanotube (CNT) surfaces. Various NMR methods were used to analyze those systems, such as chemical shift detection, spectral intensity measurements, spin relaxation and, in particular, self-diffusion experiments. Besides this, small angle X-ray scattering (SAXS) was also applied for structural characterization.   A particular form of phase transition, core freezing, was detected as a function of temperature in micelles composed by a single sort of Brij-type surfactants. In mixed micelles, that phase transition still occurs accompanied by a reversible segregation of different surfactants into distinct aggregates. Adding a hydrophobic solubilizate shifts the core freezing point to a lower temperature. Upon lowering the temperature to the core freezing point, the solubilizate is released. The temperature course of the release curves with different initial solubilizate loadings is rationalized in terms of a temperature-dependent loading capacity.   The behavior of amphiphilic dispersant molecules in aqueous dispersions of carbon nanotubes (CNTs) has been investigated with a Pluronic-type block copolymer as frequent model dispersant. Detailed dispersion curves were recorded and the distribution of the dispersant among different available environments was analyzed. The amount of dispersed CNT was shown to be defined by a complex interplay of several factors during the dispersion process such as dispersant concentration, sonication time, centrifugation and CNT loading. In the dispersion process, high amphiphilic concentration is required because the pristine CNT surfaces made available by sonication must be rapidly covered by dispersants to avoid their re-attachment. In the prepared dispersions, the competitive adsorption of possible dispersants was investigated that provided information about the relative strength of the interaction of those with the nanotube surfaces. Anionic surfactants were found to have a strong tendency to replace Pluronics, which indicates a strong binding of those surfactants.   CNTs were dispersed in an epoxy resin to prepare nanotube-polymer composites. The molecular mobility of epoxy was investigated and the results demonstrated the presence of loosely associated CNT aggregates within which the molecular transport of epoxy is slow because of strong attractive intermolecular interactions between epoxy and the CNT surface. The rheological behavior is dominated by aggregate-aggregate jamming. / <p>QC 20180103</p>

Chlorine solid-state nuclear magnetic resonance (SSNMR) is an ideal site specific probe of chloride-containing solids as SSNMR tensor properties are sensitive to the local chlorine environment. In this thesis, the development and use of chlorine SSNMR as a method to characterize a wide variety of chemical environments was explored. Ultrahigh field, and multi-field studies were essential to overcome the difficulties associated with the collection of chlorine SSNMR spectra. Benchmark chemical shift (CS) and electric field gradient (EFG) tensor data were collected for organic chloride systems, including several amino acid hydrochlorides. These experiments demonstrated the sensitivity of chlorine SSNMR to slight changes in chemical environment. Quantum chemical calculations were used to complement experimental data, with the gauge-including projector augmented wave DFT (GIPAW-DFT) method shown to yield better agreement than B3LYP or RHF methods. The GIPAW-DFT method was found to slightly, but systematically, overestimate the chlorine quadrupolar coupling constant and the CS tensor span. Other organic chlorides examined by chlorine SSMR included a known ion receptor, meso-octamethylcalix[4]pyrrole. This compound was found to have a very small quadrupole interaction (QI), but significant chemical shift anisotropy (CSA). GIPAW-DFT calculations were also utilized and, in combination with the experimental results, used to identify the solvate structure of the material analyzed by NMR. Chlorine SSNMR was further used to study different solvate structures and polymorphism. The technique was an effective means to distinguish different room temperature polymorphs of benzidine hydrochloride, despite the similarities of the chloride environments. In the case of magnesium chloride, chlorine SSNMR was sensitive to the level of hydration and through the use of GIPAW-DFT calculations, the identity of an unknown hydrate was determined. An analysis of several group thirteen chlorides demonstrated that chlorine SSNMR was also capable of characterizing the chlorine environment in cases where the QI is large, despite the resulting broad line widths. In these systems GIPAW-DFT calculations also yielded excellent agreement with experimental values. Throughout this research, chlorine SSNMR has been shown to be a useful and effective means to study both organic and inorganic chlorides, with computational methods proving to be an important complement to experimental data.

Abstract In this thesis, the classic Kurland-McGarvey theory for the nuclear magnetic resonance (NMR) chemical shift is presented in a modern framework for paramagnetic systems containing one or more unpaired electrons. First-principles computations are carried out for the NMR shielding tensors in paramagnetic transition-metal complexes. A combined ab initio/density-functional theory (DFT) approach is applied to obtain the necessary electron paramagnetic resonance (EPR) property tensors, i.e., the g-tensor, zero-field splitting tensor (D) and hyperfine coupling tensors (A). In DFT, both the generalised-gradient approximation and hybrid DFT are applied to calculate A. The complete active space self-consistent field theory (CASSCF) and N-electron valence-state perturbation theory (NEVPT2) are applied to calculate the g- and D-tensors. Scalar relativistic effects are included at the second-order Douglas-Kroll-Hess level for the g- and D-tensors and, for A, at the fully relativistic four-component matrix-Dirac-Kohn-Sham level. This methodology is applied to study ¹³C and ¹H chemical shifts and shielding anisotropies in a series of Co(II) pyrazolylborate complexes, a Cr(III) quinolyl-functionalised cyclopentadienyl complex, Ni(II) acetylacetonate complexes and various metallocenes. The results obtained from these calculations are generally in a good agreement with the experimental data, in some cases, for Ni(II) complexes, allowing to correct the experimental spectral signal assignment. CASSCF/NEVPT2 computations (especially for the D-tensor) are more accurate than DFT, which is useful for the purpose of obtaining the NMR chemical shifts. The computational results obtained are dependent on the choice of molecular geometry (experimental X-ray or computationally optimised), wavefunction used for g and D (CASSCF or NEVPT2), DFT functional for A, and the quality of the basis sets. The locally dense basis method used for the CASSCF/NEVPT2 computations is less expensive and gives equally good results for g and D as fully balanced basis sets. The scalar relativistic influences are usually small for g and D, but are large for A. Due to that, scalar relativistic effects are important for the chemical shift and shielding anisotropy, especially for carbon nuclei. These first-principles computations based on combined ab initio/DFT methodology are promising for the treatment of important electron correlation and scalar relativistic effects in the calculation of pNMR chemical shifts and shielding anisotropies. This work provides a straightforward platform for further development of pNMR shielding theory in terms of first-principles wavefunctions, as well as for applications in current problems in bio- and materials sciences, including low-temperature experiments. / Original papers The original papers are not included in the electronic version of the dissertation. Vaara, J., Rouf, S. A., &amp; Mareš, J. (2015). Magnetic Couplings in the Chemical Shift of Paramagnetic NMR. Journal of Chemical Theory and Computation, 11(10), 4840–4849. https://doi.org/10.1021/acs.jctc.5b00656 Rouf, S. A., Mareš, J., &amp; Vaara, J. (2015). ¹H Chemical Shifts in Paramagnetic Co(II) Pyrazolylborate Complexes: A First-Principles Study. Journal of Chemical Theory and Computation, 11(4), 1683–1691. https://doi.org/10.1021/acs.jctc.5b00193 Rouf, S. A., Jakobsen, V. B., Mareš, J., Jensen, N. D., McKenzie, C. J., Vaara, J., &amp; Nielsen, U. G. (2017). Assignment of solid-state ¹³C and ¹H NMR spectra of paramagnetic Ni(II) acetylacetonate complexes aided by first-principles computations. Solid State Nuclear Magnetic Resonance, 87, 29–37. https://doi.org/10.1016/j.ssnmr.2017.07.003 Rouf, S. A., Mareš, J., &amp; Vaara, J. (2017). Relativistic Approximations to Paramagnetic NMR Chemical Shift and Shielding Anisotropy in Transition Metal Systems. Journal of Chemical Theory and Computation, 13(8), 3731–3745. https://doi.org/10.1021/acs.jctc.7b00168 http://jultika.oulu.fi/Record/nbnfi-fe201801031039

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Ce mémoire présente une méthodologie théorique pour comprendre l'origine de différence de comportement dynamique de complexes alkylidènes, catalyseurs de type Schrock de la métathèse des oléfines, greffés un support de silice amorphe. Dans un travail antérieur, les différences entre les valeurs de l'anisotropie de déplacement chimique (CSA) obtenus par des mesures de RMN du solide et celles estimées par le calcul pour des systèmes figés avaient conduit à suggérer des régimes dynamiques différents pour ces complexes, certains étant proposés comme immobiles, d'autres comme mobiles. Dans le premier groupe se trouve les complexes du molybdène et dans le second les complexes du tungstène, rhénium et tantale. Dans le cadre de cette thèse, nous nous sommes donc attachés à mettre en place une méthodologie pour déterminer ces CSA et donc la nature de la dynamique de chaque système qui conduit au CSA moyenné. Nous nous sommes d'abord intéressés à des systèmes moléculaires pour révéler des interactions non covalentes entre les complexes et le support silice à partir d'une approche de type petit cluster en utilisant divers niveaux de calculs DFT et modèles moléculaires. Cette modélisation moléculaire de la silice étant insuffisante, nous avons entrepris une modélisation de la surface de silice amorphe par dynamique moléculaire classique dont les caractéristiques ont été comparées aux données expérimentales existantes. Le comportement dynamique de ces systèmes greffés sur silice amorphe a été simulé par dynamique moléculaire ab initio QM/MM, couplant une description quantique du complexe organométallique à une description classique du support. Ces études dynamiques ont conduit à des valeurs de CSA moyennées dans le temps de la dynamique. La comparaison de ces valeurs calculées et des valeurs expérimentales a permis d'apporter des éléments de réponse sur l'origine des différences de comportement dynamique de ces complexes alkylidènes. De façon remarquable des mouvements d'ensemble des espèces greffées par rapport à la surface de silice et des modifications de la coordination du métal par l'apparition d'interaction agostique contribuent à moyenner le CSA. / This work presents a theoretical study aimed at analyzing the origin of the differences in the dynamics of alkylidenes complexes, known as Schrock olefin metathesis catalysts, supported on amorphous silica. The difference between the experimental chemical shift anisotropies (CSA) obtained from solid state NMR measurements and the values computed for the most stable configurations have been used in previous work to suggest different dynamical behaviors for the supported complexes. Some of the complexes were suggested to have limited mobilities while others were suggested to be mobiles. In the first group, one finds Mo complexes, and in the second, W, Re and Ta complexes. In this thesis, a methodology was established to compute the CSA and to obtain information on the dynamics that average the CSA over time. In the first part of this work, molecular species were considered and the non covalent interactions between the surface and the grafted complexes were studied with various DFT levels of calculations and various molecular models. This molecular modeling being inappropriate, a better representation of the surface of amorphous silica was carried out with classical molecular dynamic methods. The nature of the surface was analyzed and compared with available experimental information. In a following step, the dynamic behavior of these complexes was determined using anab initio molecular dynamics (QM/MM) approach in which the metal fragments are treated at the quantum level and the support represented in a classical manner. These molecular dynamics studies yield time averaged CSA that are reasonably close to the experimental values and confirm in particular the partition into immobile (Mo) and mobile (W, Re, Ta) complexes. A detailed analysis of the results leads to a better understanding of the nature of the dynamics. Remarkably, motions relative to the silica surface and vibrations influencing the coordination sphere of the metal involving in particular agostic interactions both contribute to average the CSA.

Introdução: com o uso generalizado de métodos de imagem, aumentou-se a detecção de lesões renais como achados incidentais. Tais lesões podem ser tanto benignas, tais como os angiomiolipomas, e outras malignas, como os carcinomas de células renais, portanto torna-se importante um método não-invasivo com boa acurácia para sua distinção . A ultrassonografia é pouco específica para este fim. A tomografia computadorizada e a ressonância magnética são os métodos mais utilizados na caracterização de lesões incidentais renais. Na Ressonância Magnética, o uso de sequências convencionais ponderadas em T2W e T1W, antes e após a administração endovenosa de contraste paramagnético, mostrou-se pouco eficaz para este fim. Técnicas quantitativas associadas às imagens convencionais, tais como a oposição de fase e a restrição a difusão da água, vêm sendo estudadas, devido ao potencial para melhorar a caracterização não-invasiva, evitando nefrectomias parciais ou totais, e outras intervenções invasivas por lesões benignas. Objetivos: avaliar a acuidade diagnóstica de técnicas combinadas de ressonância magnética para diferenciação de angiomiolipomas pobres em gordura de lesões malignas do rim. Métodos: pacientes que obtiveram o diagnóstico histológico das lesões renais entre os anos de 2010 e 2014 e que realizaram exame pré-operatório. As lesões foram estudadas, colocando-se um ROI (region of interest, no inglês) na maior parte da lesão e córtex renal normal, evitando-se área de não-lesões, calculando a intensidade de sinal nas seqüências T1W in e out-phase, T2W, o Wash in, Wash out relativo e absoluto das lesões e o cálculo absoluto do sinal da lesão no ADC (coeficiente de difusão aparente, do inglês). Os resultados foram obtidos na forma de índices padronizados pelo córtex renal e baço, pelas fases pré e pós-contraste, e de forma absoluta pelo ADC. Os resultados foram confrontados com o diagnóstico final e feito associações estatísticas para observar a relevância. Resultados:Foram estudadas 85 lesões em 74 pacientes, sendo 40 do gênero masculino e 34 do feminino. O cálculo do teor de gordura se mostrou ineficaz para distinção entre CCRs e AMLpg; o índice de intensidade de sinal em T2W, lesão/córtex normal foi útil na diferenciação dos CCRs CC de AMLpg. Outro parâmetro importante foi a cálculo de wash out relativo que se mostrou mais acentuado no AMLpg que em todos os subtipos de CCRs estudados e da medida do ADC médio, que apresentou valores maiores nos casos de CCR CC, em comparação com os outros subtipos e com os AMLpg. Conclusão: As técnicas combinadas de RM, principalmente o índice de sinal T2W da lesão, Wash out relativo e IS do ADC, associados a dados epidemiológicos são viáveis, quando utilizados em conjunto, para a diferenciação de lesões malignas renais dos angiomiolipomas, podendo ter implicações na conduta terapêutica, com redução do número de nefrectomias por lesão benignas. / Introduction: With the widespread use of imaging methods, detection of incidental renal masses has steadily increased in recent years, and these may be either benign, such as angiomyolipoma, or malignant, such as renal cell carcinomas. Therefore, it is important to have a method that allows accurate characterization. Ultrassonography is not very specific for this purpose. CT and MRI are the methods used in the characterization of renal incidental lesions. In MRI, the use of conventional sequences, such as T1W and T2W before and after intravenous administration of paramagnetic contrast media, has proved ineffective for this purpose. Quantitative techniques associated with conventional images, such as chemical shift and diffusion weighted imaging (DWI), have played a key role in this differentiation, which aims to improve characterization, avoiding partial or total nephrectomy, and other invasive interventions for benign lesions. Objectives: to evaluate the diagnostic accuracy of combined techniques of MRI to differentiate fat-poor angiomyolipoma from renal cell carcinomas. Methods: Patients who had a histological diagnosis of renal lesions between 2010 and 2014 and underwent pre-operative exam. An ROI (region of interest)cwas placed in most of the lesion and normal renal cortex, avoiding area of non lesions, by calculating the signal intensity in all sequences, in and out phase T1W, T2W, and the wash in, wash out, relative and absolute, of the lesions and estimation of the ADC. The results were obtained in the form of standardized indices for renal cortex and spleen, the pre- and post-contrast phases, and absolute values for ADC. Results were confronted with the final diagnosis and statistical analysis to observe the relevancy. Results: the estimation of intracellular fat content was ineffective for characterization, while the T2W signal intensity index was used for differentiation between CCRs clear cells from fat-poor AML. Another important parameter was the \"wash out\", which was more prominent for AMLpg. ADC values was higher for CCR CC. Conclusion: We concluded that the combined techniques of MRI mainly T2W signal ratio, \"Wash out\" and ADC values, when used in association and correlated with epidemiological data may be feasible for the differentiation among fat-poor angiomyolipomas and renal malignancies, with important therapeutics implications, reducing unnecessary nephrectomies for benign lesions.

A fosfatase Cdc25B atua na progressão do ciclo celular através da ativação de complexos Cdk/Ciclina. Atualmente, nos modelos estruturais propostos do domínio catalítico da Cdc25B não estão incluídos os últimos 16 resíduos da região C-terminal. Este segmento tem importante papel no reconhecimento do substrato proteico e pode estar envolvido na complexação de pequenas moléculas com a Cdc25B. Assim, o principal objetivo desta tese foi avaliar a flexibilidade conformacional do domínio catalítico completo da Cdc25B em solução através de simulações computacionais e por medidas experimentais de ressonância magnética nuclear (RMN). A similaridade entre as estruturas cristalográficas e em solução foi confirmada pela previsão de ângulos diedrais &#966;/&#968; da cadeia principal a partir dos deslocamentos químicos (CS) e pela concordância entre os acoplamentos dipolares residuais (RDC) medidos e calculados a partir da geometria cristalina. Medidas de parâmetros de relaxação de 15N e RDC evidenciaram a presença de desordem conformacional na região C-terminal, em acordo com a ausência de densidade eletrônica desse segmento no experimento de difração de raios-X. Através da comparação entre CS experimentais e previstos de simulações de dinâmica molecular (DM) longas (total de 6&#181;s de duração) foram apontados artefatos de cristalização, possíveis erros nos campos de força usados nas simulações, falhas na composição do sistema simulado e estados conformacionais populados pela Cdc25B em solução distintos da geometria cristalográfica. De maneira geral, os CS previstos a partir das simulações para a flutuação estrutural dos resíduos da região C-terminal desordenada estão em acordo com os valores experimentais, sugerindo que os estados conformacionais deste segmento foram razoavelmente bem amostrados nas simulações. Em particular, verificou-se que o contato tipo cátion-&#960; entre as cadeias laterais dos resíduos 550W do C-terminal desordenado e 482R do núcleo proteico, ausente na estrutura cristalográfica, pode ser importante em solução. A formação desse contato na simulação de DM também está de acordo com medidas experimentais de perturbação de deslocamentos químicos (CSP) entre construções completa e truncada do domínio catalítico da Cdc25B. Assim, através do uso conjunto de simulações computacionais e medidas experimentais foi possível obter uma representação mais completa e realista da flexibilidade conformacional do domínio catalítico da Cdc25B em solução, incluindo a determinação de possíveis contatos intramoleculares entre a região C-terminal desordenada e o núcleo proteico. Essas informações poderão ser usadas na construção de um ensemble conformacional da Cdc25B. / Cdc25B phosphatase acts on the progression of cell cycle through the activation of Cdk/Cyclin complexes. Currently, the proposed structural models of Cdc25B catalytic domain lack the last 16 residues from the C-terminal region. This segment is important for protein substrate recognition and might be involved in small molecule binding to Cdc25B. Thus, the main goal of this thesis was to evaluate the conformational flexibility of the complete catalytic domain from Cdc25B through computer simulations and experimental nuclear magnetic resonance (NMR) measurements. Similarity between crystal and in solution structures was confirmed by the prediction of backbone &#966;/&#968; dihedral angles from chemical shifts (CS) and by the agreement between observed and back-calculated residual dipolar couplings (RDC). 15N relaxation and RDC measurements pointed to the conformational disorder of the C-terminal region, in agreement with the X-ray diffraction experiment where this segment showed no electronic density. Comparison between experimental and predicted CS from long molecular dynamics (MD) simulations (6&#181;s total running time) pointed to the presence of crystallographic artifacts, possible deficiencies in simulation force fields, inaccurate composition of the simulated system and conformational states visited by Cdc25B in solution that were not observed in the crystallographic geometry. Generally, CS predicted from simulations for the structural fluctuation of the disordered C-terminal region were in agreement with experimental values, suggesting that the simulations sampled the conformational states populated by this segment reasonably well. In particular, a cation-&#960; contact not observed in the crystal structure between side chains of residue 550W from the disordered C-terminal tail and residue 482R from the protein core might be important in solution. This contact is also in agreement with experimental chemical shift perturbations (CSP) measured between complete and truncated constructs of Cdc25B catalytic domain. Therefore, the joint use of computer simulations and experimental measurements allowed the achievement of a more complete and realistic representation of the conformational flexibility of the Cdc25B catalytic domain in solution, including intramolecular contacts between the disordered C-terminal region and the protein core. This information might be used to obtain a conformational ensemble of Cdc25B.

A new family of oligonuclear cyano compounds incorporatingtransition (Pt) and main group (Tl) metals bound with anon-buttressed Pt-Tl bond was synthesised in aqueous solution.The metal-metal linkage is formed in the reaction betweenplatinum and thallium in their stable oxidation forms, Pt(II)and Tl(III), orvice versa: Pt(IV) and Tl(I). Four binuclear complexeswith a general composition [(CN)5Pt-Tl(CN)n(aq)]n-(n = 0-3) and a trinuclear species [(NC)5Pt-Tl-Pt(CN)5]3-were identified and structurally characterised insolution by multinuclear NMR, EXAFS and vibrationalspectroscopy. In aqueous solution the complexes exist inequilibrium. The distribution between the species can bealtered by varying the molar ratio Pt/Tl, cyanide concentrationand pH. Stability constants of the compounds weredetermined. A new compound (NC)5PtTl was also prepared in solid and its crystalstructure solved by a combination of X-ray powder diffractionand EXAFS. Altogether the values of195Pt-205Tl spin-spin coupling constants (25-71 kHz),interatomic Pt-Tl distances (2.598-2.638 Å), and vibrationstretching frequencies v (Pt-Tl) (159-164 cm-1) are fully indicative of a direct and unsupportedPt-Tl bond. The calculated values of Pt-Tl force constants(1.56-1.74 N· cm-1) are characteristic for single metal-metal bond.The oxidation status in the compounds can be viewed asintermediate between II and IV for platinum, and between I andIII for thallium, as reflected by the chemical shifts of195Pt and205Tl nuclei, C≡ N stretching frequencies andelectron binding energies. The compounds are capable to undergo a photoinducedtwo-electron transfer between the coupled hetero-metal ions.Upon irradiation into the metal-to-metal charge transferabsorption band, effective photoredox reaction takes place. Itresults in scission of the Pt-Tl bond and formation of variouscomplexes of oxidised platinum (Pt(III, IV)) and reducedthallium (Tl(I)). The values of photodecomposition quantumyields were determined from a stationary photolysis study ofthe heterometallic complexes. Nanosecond laser flash photolysisof the heteronuclear Pt-Tl cyano compounds was performed in thetimescale range 1· 10-6- 5· 10-2s and several intermediate species were detectedand characterised by optical spectroscopy. The heteronuclear Pt-Tl cyano compounds can be furthermodified in terms of their stability, solubility, and lightabsorption characteristics. It has been found that the platinumpentacyano unit of the [(NC)5Pt-Tl(CN)n(aq)]n-species is inert towards the tested ligands,whereas the thallium "part" of the complexes can be tunedsignificantly. A number of complexes [(NC)5Pt-Tl(L)m]x-(L-ligand) were prepared and characterised insolution. Compounds [(NC)5Pt-Tl(nta)(H2O)]3-, [(NC)5Pt-Tl(bipy)(DMSO)3], and [(NC)5Pt-Tl(bipy)2]have been prepared in solid and their structuresdetermined by single-crystal X-ray diffraction. <b>Keywords:</b>thallium, platinum, cyanide, metal-metal bond,non-buttressed, heterobimetallic, photoinduced, electrontransfer, redox reaction, NMR, chemical shift, spin-spincoupling constant, Raman, EXAFS, X-ray diffraction,equilibrium, oxidation state, oxidative addition,photolysis

<p>A new family of oligonuclear cyano compounds incorporatingtransition (Pt) and main group (Tl) metals bound with anon-buttressed Pt-Tl bond was synthesised in aqueous solution.The metal-metal linkage is formed in the reaction betweenplatinum and thallium in their stable oxidation forms, Pt(II)and Tl(III), or<i>vice versa</i>: Pt(IV) and Tl(I). Four binuclear complexeswith a general composition [(CN)₅Pt-Tl(CN)_n(aq)]^n-(n = 0-3) and a trinuclear species [(NC)₅Pt-Tl-Pt(CN)₅]^3-were identified and structurally characterised insolution by multinuclear NMR, EXAFS and vibrationalspectroscopy. In aqueous solution the complexes exist inequilibrium. The distribution between the species can bealtered by varying the molar ratio Pt/Tl, cyanide concentrationand pH. Stability constants of the compounds weredetermined.</p><p>A new compound (NC)₅PtTl was also prepared in solid and its crystalstructure solved by a combination of X-ray powder diffractionand EXAFS. Altogether the values of¹⁹⁵Pt-²⁰⁵Tl spin-spin coupling constants (25-71 kHz),interatomic Pt-Tl distances (2.598-2.638 Å), and vibrationstretching frequencies v (Pt-Tl) (159-164 cm^-1) are fully indicative of a direct and unsupportedPt-Tl bond. The calculated values of Pt-Tl force constants(1.56-1.74 N· cm^-1) are characteristic for single metal-metal bond.The oxidation status in the compounds can be viewed asintermediate between II and IV for platinum, and between I andIII for thallium, as reflected by the chemical shifts of¹⁹⁵Pt and²⁰⁵Tl nuclei, C≡ N stretching frequencies andelectron binding energies.</p><p>The compounds are capable to undergo a photoinducedtwo-electron transfer between the coupled hetero-metal ions.Upon irradiation into the metal-to-metal charge transferabsorption band, effective photoredox reaction takes place. Itresults in scission of the Pt-Tl bond and formation of variouscomplexes of oxidised platinum (Pt(III, IV)) and reducedthallium (Tl(I)). The values of photodecomposition quantumyields were determined from a stationary photolysis study ofthe heterometallic complexes. Nanosecond laser flash photolysisof the heteronuclear Pt-Tl cyano compounds was performed in thetimescale range 1· 10^-6- 5· 10^-2s and several intermediate species were detectedand characterised by optical spectroscopy.</p><p>The heteronuclear Pt-Tl cyano compounds can be furthermodified in terms of their stability, solubility, and lightabsorption characteristics. It has been found that the platinumpentacyano unit of the [(NC)₅Pt-Tl(CN)_n(aq)]^n-species is inert towards the tested ligands,whereas the thallium "part" of the complexes can be tunedsignificantly. A number of complexes [(NC)₅Pt-Tl(L)_m]^x-(L-ligand) were prepared and characterised insolution. Compounds [(NC)₅Pt-Tl(nta)(H₂O)]^3-, [(NC)₅Pt-Tl(bipy)(DMSO)₃], and [(NC)₅Pt-Tl(bipy)₂]have been prepared in solid and their structuresdetermined by single-crystal X-ray diffraction.</p><p><b>Keywords:</b>thallium, platinum, cyanide, metal-metal bond,non-buttressed, heterobimetallic, photoinduced, electrontransfer, redox reaction, NMR, chemical shift, spin-spincoupling constant, Raman, EXAFS, X-ray diffraction,equilibrium, oxidation state, oxidative addition,photolysis</p>