Orientador: René Alfonso Nome Silva / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-25T09:25:13Z (GMT). No. of bitstreams: 1 Ferbonink_GuilhermeFerreira_M.pdf: 3339040 bytes, checksum: ef20418e159acb6b4683d177155e28be (MD5) Previous issue date: 2014 / Resumo: Nos últimos anos, várias descobertas vêm sendo realizada sobre como características intrínsecas de um dado sistema podem afetar a transferência eletrônica de energia. Um dos objetivos desta pesquisa é estudar experimentalmente como a estrutura vibrônica pode afetar a transferência eletrônica de energia em moléculas orgânicas segundo o modelo de Förster. Utilizando um sistema molecular com sobreposição espectral sobre bandas vibrônicas bem definidas, podemos verificar experimentalmente que o abaixamento da intensidade de emissão do doador unicamente nos comprimentos de onda de absorção do receptor caracteriza transferência de energia pelo modelo emissivo. Abaixamento da intensidade integrada de emissão caracteriza transferência de energia pelo mecanismo de Förster. A taxa de transferência de energia pelo mecanismo de Förster foi mais significativa quando a sobreposição espectral ocorre nas bandas vibrônica 0-1,0-2 ao invés da banda 0-0. Na segunda parte do trabalho realizado, aplicamos a técnica de absorção transiente para o estudo de nano prismas de ouro depositados sobre dois substratos diferentes. Neste trabalho, nós descrevemos a preparação e caracterização de matrizes isoladas de nanoprismas triangulares de ouro sobre o vidro contendo uma camada de ITO por litografia de nanoesferas. O espectro de absorção linear de Au / vidro e Au / ITO / vidro exibe ressonância de plásmon de superfície em 800 nm e 870 nm, com um deslocamento para o vermelho de 70 nm associado ao índice de refração de ITO. Foram realizadas medidas de espectroscopia de uma única cor de bombeio e prova com resolução temporal de 100 fs em comprimentos de onda inferiores a ressonância, em ressonância, e acima da ressonância de plásmon de superfície para cada um destes dois sistemas. A dinâmica ultra-rápida em ambos os sistemas pode ser bem descrita com um modelo que contabiliza o espalhamento elétron-elétron, o acoplamento elétron-fônon, e oscilações acústicas no término do resfriamento da estrutura de ouro. Os resultados para as nanopartículas de ouro, para cada um dos comprimentos de onda são bem descritos como tendo índice de refração complexo com dependência do comprimento de onda, que modula os sinais de bombeio e prova medidos / Abstract: Structure-property relationships for electronic energy transfer have been investigated in recent years. One of the goals of the present research is to perform an experimental study vibronic structure effects in electronic energy transfer between small organic molecules according to Forster¿s model. We have chosen organic molecules with well-defined spectral overlap between vibronic bands, which enabled us to experimentally characterize a decrease in donor emission intensity at the acceptor absorption wavelengths thereby indicating radiative energy transfer. A decrease in the emission integrated intensity characterizes energy transfer by the Forster mechanism. Forster energy transfer rates were higher when the spectral overlap involved 0-1 and 0-2 vibronic bands rather than 0-0 band. In the second part of this work, we have employed ultrafast transient absorption spectroscopy to investigated gold nano prisms deposited over two different substrates: Au over glass (Au/glass) and Au over ITO deposited on glass (Au/ITO/glass). In the present work, we describe the preparation and characterization of these two samples employing the nanosphere lithography technique. The linear absorption spectra of Au/glass and Au/ITO/glass respectively show surface plasmon resonances at 800 nm and 870 nm, with a 70nm redshift attributed to the ITO refractive index. We have performed femtosecond one-color pump-probe measurements with 100 fs time resolution below the surface plasmon resonance, at resonance, and above the surface plasmon resonance for each of these two systems. For both systems, the ultrafast dynamics can be well described with a model that takes into account electron-electron scattering, electron-phonon coupling, phonon-phonon coupling and acoustic damping. The wavelength-dependence observed can be explained in terms of the sample frequency-dependent complex refractive index which modulates the measured pump-probe signals / Mestrado / Físico-Química / Mestre em Química

Les propriétés optoélectroniques de jonctions moléculaires sont étudiées par microscopie à effet tunnel (STM). Premièrement, les structures moléculaires sont synthétisées sur une surface Au(111). Puis, par manipulation, nous soulevons et suspendons une molécule entre la pointe du STM et la surface d’or pour obtenir une jonction moléculaire. En appliquant une tension entre la pointe et l'échantillon, un courant est généré, ce qui conduit à l'excitation de la molécule. Ce processus est médié par des modes de plasmons de surface localisé de la pointe. Finalement, la molécule se désexcite de manière radiative et génère un signal de fluorescence. On utilise cette technique pour étudier deux systèmes moléculaires. Dans le premier, un émetteur (porphyrin) est suspendu dans la jonction grâce à des fils organiques (oligothiophène). Ce type de jonction génère une émission de lumière étroite dont la couleur est contrôlée en sélectionnant la structure chimique de l'émetteur. Le contrôle de la largeur du pic d’émission est obtenu en détachant progressivement l'unité émettrice de la surface. On observe aussi des pics vibroniques décalés vers le rouge qui fournissent une empreinte chimique de l’émetteur, et des pics décalés vers le bleu, signe d’une deséxcitation d’un exciton non-thermalisé. Le deuxième type de jonction est composé de nano-rubans de graphène (GNRs) dont la largeur et la structure de l’arrête sont définis avec une précision atomique. Une fois suspendu dans la jonction, les GNRs qui présentent une terminaison spécifique (terminaison C) montrent un spectre d’émission de lumière avec un pic principal et deux pics vibroniques décalés vers le rouge. Le pic principale est associé à une transition intra-ruban entre un état Tamm localisé et un état delocalisé. / This thesis presents a study of the optoelectronic properties of molecular junctions performed by scanning tunneling microscopy (STM). First, the molecular structures are synthesized on a Au(111) surface. Then, by manipulation we lift and suspend a molecule between the tip of the STM and the gold surface, creating a single molecule junction. By applying a voltage bias between the tip and the sample, a current is generated, which leads to the excitation of the molecule. This process is mediated by the localized surface plasmon modes of the tip. Eventually, the molecule de-excites in a radiative way, generating a fluorescence signal. We use this technique to study two different molecular junctions. First, an emitting unit (fused-porphyrin) is suspended in the junction by means of organic linkers (oligothiophene). This type of junction generates a narrow-line emission of light whose color is controlled by selecting the chemical structure of the emitting unit. Moreover, control over the linewidth is obtained by progressively detaching the emitting unit from the surface. Also, we observe red-shifted vibronic features that provide a chemical fingerprint of the emitter, and blue- shifted vibronic features that are a sign of hot-luminescence. For the second type of junctions we use graphene nanoribbons (GNRs) of atomically precise width and edge structure. When lifted in the junction, GNRs with a specific type of termination (C-terminated) exhibit a light emission spectrum with a main peak and two red-shifted vibrational features. The main peak is associated to an intra-ribbon transition between a localized state (Tamm) and a delocalized state.

This thesis describes the development of several spectroscopic methods based on impulsive vibrational spectroscopy as well as of the technique itself. The first chapter describes the ultrafast time domain Raman spectrometer including the development of two noncollinear optical parametric amplifiers for sub-10 fs pulse generation with 343 or 515 nm pumping. In the first spectroscopic study we demonstrate, for the first time, that impulsive vibrational spectroscopy can be used for recording transient Raman spectra of molecules in excited electronic states. We obtain spectra of beta-carotene with comparable, or better, quality than established frequency domain based nonlinear Raman techniques. The following two chapters address the questions on the fate of vibrational coherences when generated on a reactive potential energy surface. We photoexcite bacteriorhodopsin and observe anharmonic coupling mediated vibrational coherence transfer to initially silent vibrational modes. Additionally, we are able to correlate the vibrational coherence activation with the efficiency of the isomerisation reaction in bR. Upon generation of vibrational coherence in the second excited electronic state of beta-carotene, by excitation from the ground electronic state, we are able to follow the wavepacket motion out of the Franck-Condon region. We observe vibrationally coherent internal conversion, through a conical intersection, into the first excited electronic state and are hence able to demonstrate that electronic surface crossings can occur in a vibrationally coherent fashion. Additionally, we find strong evidence for vibronic coupling mediated back and forth crossing between the two electronic states. As a combination of this work we develop a IVS based technique that allows for the direct recording of background and baseline free Raman spectra in the time domain. Several proof of principle experiments highlight the capabilities of this technique for time resolved Raman spectroscopy. In the final chapter we present work on weak-field coherent control. Here, we address the question of whether a photochemical reaction can be controlled by the phase term of an electric excitation field, in the one photon excitation limit. We study the systems rhodamine 101, bacteriorhodopsin, rhodopsin and isorhodopsin and, contrary to previous reports, find no evidence for one photon control.

No description available.

In this thesis a reduced dimensionality quantum scattering model is applied to the study of polyatomic reactions of type X + CH4 <--> XH + CH3. Two dimensional quantum scattering of the symmetric hydrogen exchange reaction CH3+CH4 <--> CH4+CH3 is performed on an 18-parameter double-Morse analytical function derived from ab initio calculations at the CCSD(T)/cc-pVTZ//MP2/cc-pVTZ level of theory. Spectator mode motion is approximately treated via inclusion of curvilinear or rectilinear projected zero-point energies in the potential surface. The close-coupled equations are solved using R-matrix propagation. The state-to-state probabilities and integral and differential cross sections show the reaction to be primarily vibrationally adiabatic and backwards scattered. Quantum properties such as heavy-light-heavy oscillating reactivity and resonance features significantly influence the reaction dynamics. Deuterium substitution at the primary site is the dominant kinetic isotope effect. Thermal rate constants are in excellent agreement with experiment. The method is also applied to the study of electronically nonadiabatic transitions in the CH3 + HCl <--> CH4 + Cl(2PJ) reaction. Electrovibrational basis sets are used to construct the close-coupled equations, which are solved via Rmatrix propagation using a system of three potential energy surfaces coupled by spin-orbit interaction. Ground and excited electronic surfaces are developed using a 29-parameter double-Morse function with ab initio data at the CCSD(T)/ccpV( Q+d)Z-dk//MP2/cc-pV(T+d)Z-dk level of theory, and with basis set extrapolated data, both corrected via curvilinear projected spectator zero-point energies. Coupling surfaces are developed by fitting MCSCF/cc-pV(T+d)Z-dk ab initio spin orbit constants to 8-parameter functions. Scattering calculations are performed for the ground adiabatic and coupled surface models, and reaction probabilities, thermal rate constants and integral and differential cross sections are presented. Thermal rate constants on the basis set extrapolated surface are in excellent agreement with experiment. Characterisation of electronically nonadiabatic nonreactive and reactive transitions indicate the close correlation between vibrational excitation and nonadiabatic transition. A model for comparing the nonadiabatic cross section branching ratio to experiment is discussed.

This work tries to show the significant competence and functionality of density functional theory (DFT) and time-dependent density functional theory (TD-DFT) as theoretical approaches, supporting experimental measurements in various fields of physics from astrophysics to surface science, to study the electronic structure and spectroscopic properties of molecules and clusters: Silicon nanocrystals: Due to their optical properties, silicon nanocrystals have attracted considerable attention in astrophysics. In this work, the optical properties of H-passivated silicon nanocrystals are determined by the energetics of the frontier orbitals and their dependence on the deformation in the relaxed excited state, using DFT and TD-DFT. The Jahn-Teller effect in the lowest excited state results in a distortion toward tetragonal symmetry, contributing significantly to the red shift of the photoluminescence (PL) spectra. Therefore, the deformation in the relaxed excited state consists of a symmetry conserving part and of a symmetry-breaking distortion from Td toward D2d. For nanocrystals up to a diameter of 1.5 nm, we project the deformations at the minima of the excited state potential surface onto the different symmetries, allowing for a discrimination of the respective contributions to the total Stokes shift. The results show a quantitative agreement between the TD-DFT calculations of PL gap and the observed PL energies better than 0.2 eV. It is also seen that the large PL linewidth is the fundamental property of each cluster, not of ensemble average over clusters of different size. 2,3-Benzofluorene: We have presented new theoretical results on the absorption spectroscopy of 2,3-benzofluorene (Bzf) for the transition from the ground state, S0, to the first electronically excited singlet state, S1, to support the measurements of S1(1A´) <- S0(1A´) absorption spectrum of jet-cooled Bzf. The potential energy surfaces (PESs) of the S(n=0,1,2) states of Bzf have been investigated with calculations based on DFT and TD-DFT. At the B3LYP/TZ level of theory, TD-DFT does not deliver a realistic difference between the excited S1 and S2 potential energy surfaces, a problem which can be avoided by introducing a reference geometry (q*) where this difference coincides with the observation. In this geometry, an expression for the Herzberg-Teller corrected intensities of the vibronic bands is proposed, allowing a straightforward assignment of the observed a′ modes below 900 cm−1, including realistic calculated intensities. In spite of the difficulties caused by the small energy difference between the S1 and S2 states, we have obtained a reasonable theoretical absorption spectrum based on a TD-DFT approach applied to the slightly modified molecular geometry. Although the agreement between the theoretical and observed spectra is very good only for vibrational modes with frequencies lower than 900 cm−1, we consider our calculations to be the best approach to an ab initio study realized for Bzf until now since only parametrized force fields had been used before. (Ni–, Pd–, Pt–) Phthalocyanine: We studied the HOMO–LUMO gap shrinking in order to investigate the tip-induced polarization in scanning tunneling spectroscopy (STS) of d8 (Ni, Pd, and Pt) phthalocyanines. By means of DFT, the electronic structure and vibronic properties of single neutral NiPc, PdPc, and PtPc and their singly and doubly ionized cations and anions have been calculated. Interestingly, the position of the HOMO decreases systematically with increasing the atomic number of the central metal atom. The first ionization energies of neutral molecules increase by changing the central metal atom, while the electron affinities remain constant. This causes an increase in the HOMO–LUMO gap. These results show a clear correlation to experimental observations. Furthermore, partitioning of the reorganization energy, corresponding to the photoelectron spectra of the first and second ionizations of studied molecules, into normal mode contributions shows that the major contributions are due to several vibrational modes with a1g symmetry and energies lower than 1600 cm−1. The results reveal that the reorganization energy due to the singly positive ionization in the studied molecules is about one order of magnitude less than other reorganization energies, which makes these metal–phthalocyanines more attractive as electron donor for intramolecular electron transfer in electron acceptor–donor systems.

Les travaux présentés dans cette thèse peuvent être divisés en deux parties. Dans une première partie, nous avons étudié le processus de photoisomérisation dans plusieurs systèmes. Une analyse de structure électronique accompagnée d’un calcul préliminaire de dynamique semi-classique ont été appliqué à un modèle minimal du rétinal afin d’extraire les degrés de libertés les plus importants lors de l’isomérisation. Cela dans le but de construire des surfaces d’énergie potentielle diabatiques pour effectuer une étude de dynamique quantique. Une approche de type dynamique semi-classique a été appliquée à un modèle de moteur moléculaire dans le but d’étudier l’origine de l’uni-directionalité de sa rotation. Finalement, une étude de structure électronique d’un complexe de Rhénium contenant un ligand de type rétinal a été effectué pour étudier l’influence du métal sur la spectroscopie du ligand rétinal. Dans une deuxième partie nous nous sommes intéressés à l’étude des croisements intersystème dans un complexe de Rhénium. Afin de pouvoir apporter une explication à un comportement contrintuitif de ce complexe, nous avons développé un Hamiltonien modèle capable de tenir compte des couplages vibroniques interétats et spin-orbit. Cet Hamiltonien a été testé sur ce-dit système, et nous a permis, grâce à une étude de structure électronique de proposer un mécanisme de relaxation différent de celui proposé expérimentalement. / This thesis can be divided in two parts.In the first one, we have studied the photoisomerization process in several systems. An electronic structure analysis mixed with a preliminary semi-classical dynamics investigation has been applied to a minimal model of the retinal chromophore in order to select the most important degrees of freedom involved in the process. The goal of this is to build diabatic potential energy surfaces in order to conduct quantum dynamics simulations. A semi-classical approach has also been applied to a molecular motor model to study the origin of the unidirectionality of its rotary motion. Finally, an electronic structure of a rhenium complex with a retinal-like ligand has been performed to study the effect of the coordination to a metallic atom on the spectroscopy of the retinal ligand. In the second part, we have investigated the intersystem crossings in a rhenium complex. In order to bring an explanation to an experimentally observed conterintuitive behavior of this complex, we have developed a model Hamiltonian that includes both interstate vibronic coupling and spin-orbit coupling. This Hamiltonian has been tested on the said complex and, in complement to an electronic structure study, allowed us to formulate a decay mechanism different from the one proposed based on experiments.

No description available.

This work tries to show the significant competence and functionality of density functional theory (DFT) and time-dependent density functional theory (TD-DFT) as theoretical approaches, supporting experimental measurements in various fields of physics from astrophysics to surface science, to study the electronic structure and spectroscopic properties of molecules and clusters: Silicon nanocrystals: Due to their optical properties, silicon nanocrystals have attracted considerable attention in astrophysics. In this work, the optical properties of H-passivated silicon nanocrystals are determined by the energetics of the frontier orbitals and their dependence on the deformation in the relaxed excited state, using DFT and TD-DFT. The Jahn-Teller effect in the lowest excited state results in a distortion toward tetragonal symmetry, contributing significantly to the red shift of the photoluminescence (PL) spectra. Therefore, the deformation in the relaxed excited state consists of a symmetry conserving part and of a symmetry-breaking distortion from Td toward D2d. For nanocrystals up to a diameter of 1.5 nm, we project the deformations at the minima of the excited state potential surface onto the different symmetries, allowing for a discrimination of the respective contributions to the total Stokes shift. The results show a quantitative agreement between the TD-DFT calculations of PL gap and the observed PL energies better than 0.2 eV. It is also seen that the large PL linewidth is the fundamental property of each cluster, not of ensemble average over clusters of different size. 2,3-Benzofluorene: We have presented new theoretical results on the absorption spectroscopy of 2,3-benzofluorene (Bzf) for the transition from the ground state, S0, to the first electronically excited singlet state, S1, to support the measurements of S1(1A´) <- S0(1A´) absorption spectrum of jet-cooled Bzf. The potential energy surfaces (PESs) of the S(n=0,1,2) states of Bzf have been investigated with calculations based on DFT and TD-DFT. At the B3LYP/TZ level of theory, TD-DFT does not deliver a realistic difference between the excited S1 and S2 potential energy surfaces, a problem which can be avoided by introducing a reference geometry (q*) where this difference coincides with the observation. In this geometry, an expression for the Herzberg-Teller corrected intensities of the vibronic bands is proposed, allowing a straightforward assignment of the observed a′ modes below 900 cm−1, including realistic calculated intensities. In spite of the difficulties caused by the small energy difference between the S1 and S2 states, we have obtained a reasonable theoretical absorption spectrum based on a TD-DFT approach applied to the slightly modified molecular geometry. Although the agreement between the theoretical and observed spectra is very good only for vibrational modes with frequencies lower than 900 cm−1, we consider our calculations to be the best approach to an ab initio study realized for Bzf until now since only parametrized force fields had been used before. (Ni–, Pd–, Pt–) Phthalocyanine: We studied the HOMO–LUMO gap shrinking in order to investigate the tip-induced polarization in scanning tunneling spectroscopy (STS) of d8 (Ni, Pd, and Pt) phthalocyanines. By means of DFT, the electronic structure and vibronic properties of single neutral NiPc, PdPc, and PtPc and their singly and doubly ionized cations and anions have been calculated. Interestingly, the position of the HOMO decreases systematically with increasing the atomic number of the central metal atom. The first ionization energies of neutral molecules increase by changing the central metal atom, while the electron affinities remain constant. This causes an increase in the HOMO–LUMO gap. These results show a clear correlation to experimental observations. Furthermore, partitioning of the reorganization energy, corresponding to the photoelectron spectra of the first and second ionizations of studied molecules, into normal mode contributions shows that the major contributions are due to several vibrational modes with a1g symmetry and energies lower than 1600 cm−1. The results reveal that the reorganization energy due to the singly positive ionization in the studied molecules is about one order of magnitude less than other reorganization energies, which makes these metal–phthalocyanines more attractive as electron donor for intramolecular electron transfer in electron acceptor–donor systems.

As the third generation of luminescent materials, thermally activated delayed fluorescence (TADF)-type compounds have great potential as emitter molecules in OLEDs allowing for electro-fluorescence with 100 % internal quantum efficiency. For organic electronics, the general wide range of applications from OLEDs, bio-fluorescence imaging to sensor technologies and photonic energy storages roots on the enormous variety of organic materials. Especially in the field of metal- free aromatic designs, the range of possible materials showing diverse triplet harvesting effects is immense, making material development a highly complex task. Firstly, initial efforts in the understanding of the basic concepts behind TADF will be highlighted. A rational design strategy for TADF materials will be illustrated on an innovative material series based on phenylcarbazoles. A reasonable branch of isomers are theoretically constructed and slight stoichiometric modifications are performed to understand how molecular structure and intramolecular steric hindrance affects reverse intersystem crossing (RISC), while simultaneously revealing the strategy for deep blue TADF. The rational design of a bluish green TADF material called 5CzCF3Ph providing CIEy ≤ 0.4 is demonstrated, enabling peak EQE values of 12.1 % with a promising LT50 of 2 hrs at 500 cd∙m-2. Subsequently, the photophysics of five newly designed trimeric donor (D)-acceptor (A)-donor (D) type material compounds, analogue concepts to archetypical TADF designs, highlight the importance of intramolecular electronic couplings between adjacent triplet states for adiabatically-driven TADF, revealing the mechanism of local type triplet state perturbations on 3CT states. The most promising candidate (DMAC-PTO-DMAC) is disclosed and in turn optimized to meet required conditions for deep blue TADF emission. Ultimately, a deep blue luminescent material called isoDMAC-PTO is developed, featuring CIE coordinates of (0.16, 0.14) with an overall quantum yield of (86.4 ± 0.5) %. The focus switches to the fundamental understanding of the underlying mechanism giving rise to TADF in small molecules, leaving the scope of deep blue emission. While investigating the photophysical properties of a synthesized donor (D)-acceptor (A) type thermally activated delayed fluorescence (TADF) emitter named methyl 2-(9,9-dimethylacridin-10-yl)benzoate (DMAC-MB), it is possible to identify the excited state dynamics mediating the spin-flip process and hence the reutilization of non-radiative triplet states allowing for an internal quantum efficiency approaching unity. As experimentally observed by detailed temperature- and time-dependent transient photoluminescence (PL) measurements and consolidated by comprehensive quantum-chemical considerations, excited state configuration interaction by non-adiabatic couplings are anticipated as key property behind triplet up-conversion in the vicinity of conical intersections, contributing to recent research facing the exciton management within the auspicious field of TADF. For the first time, this thesis reports that even a TADF-silent molecule can be converted into efficient TADF systems by increasing the donor π- conjugation length through polymerization of the building block itself. With a total photoluminescence quantum yield up to 71 %, comprehensible research illustrates an efficient thermally activated delayed fluorescence polymer P1, based solely on non-TADF chromophores represented by a model compound 2 (PLQY of 3 % at RT). Finally, as predicted by TDDFT calculations and shown for the first time in the aspiring field of TADF, a thermally activated delayed fluorescence polymer based on a merely radiative, solely phosphorescent repeating unit is demonstrated. Intramolecular π-conjugation is exploited to trigger the charge-transfer excited state energy, revealing a general design tool to provoke TADF, reserved in particular for polymers. While the introduced twisted methyl 2-(9,9-dimethylacridin-10-yl) benzoate (DMAC-MB) reveals efficient thermally activated delayed fluorescence (TADF), a modified analogue 9,9-Dimethyl-5H,9H-quinolino[3,2,1-de]acridin-5-one (DMAC-ACR) shows emerging room temperature phosphorescence (RTP). As for TADF, intramolecular non-adiabatic couplings are unlocked as key feature actuating persistent RTP, linking photophysical analogies between TADF and RTP to structural self-similarities. Last but not least, degradation processes in TADF materials will be addressed. A correlation between theoretically calculated bond-dissociation energies (BDEs) and phenomenological observations reveals that low BDEs, in particular along pronounced charge-transfer bonds, ultimately lead to irreversible TADF material degradation induced by bi-molecular processes comprising TPQ as well as TTA. Finally, this thesis reveals the photophysics of 24 newly designed, synthesized and characterized TADF materials and demonstrates a fundamentally new approach for RTP, based on structural analogues to TADF. Far reaching design principles as conjugation induced TADF in polymers, as well as new design strategies selectively incorporating virbonic couplings yield device performances comprising LT50 of 2 hrs at 500 cd∙m-2 and targeted deep blue emission with CIE (0.16, 0.14). While lighting the way for TADF as future luminescent OLED materials, intrinsic material instabilities due to low bond-dissociation energies are disclosed as key-issues for tomorrows research.