
David CasanovaDonostia International Physics Center | DIPC
David Casanova
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Publications (200)
Organelle-selective photodynamic therapy (PDT) has emerged as a promising approach to enhance the precision and efficacy of cancer treatment by targeting key cellular structures. In this study, we report the design of a novel carnitine-based BODIPY photosensitizer, probe 1, which retains mitochondrial selectivity while acting as both a fluorescent...
Photochemical upconversion by annihilation of two triplet excitons to a higher-energy singlet state enables energy control of photons in optoelectronics and photonics. Upconversion initiated by closed-shell sensitisers is limited by energy losses from singlet–triplet intersystem crossing. Here we explore open-shell organic radicals as sensitisers t...
We have prepared a series of bis(semiquinone) compounds with dithiophene bridges of different length that evolve from closed‐shell (smaller compound) to full diradical (longer compound) for which the narrow singlet‐triplet energy gap allows the triplet population at 298 K. The medium size system has a variety of photonic properties with absorptions...
We have prepared a series of bis(semiquinone) compounds with dithiophene bridges of different length that evolve from closed‐shell to full diradical character on the basis of the narrow singlet‐triplet energy gaps which allows the triplet population at 298 K for the longer compound. The medium size compound has a variety of photonic properties with...
The development of luminescent organic radicals has resulted in materials with excellent optical properties for near-infrared emission. Applications of light generation in this range span from bioimaging to surveillance. Although the unpaired electron arrangements of radicals enable efficient radiative transitions within the doublet-spin manifold i...
The adaptive derivative-assembled pseudo-Trotter variational quantum eigensolver (ADAPT-VQE) has emerged as a pivotal promising approach for electronic structure challenges in quantum chemistry with noisy quantum devices. Nevertheless, to surmount existing technological constraints, this study endeavors to enhance ADAPT-VQE’s efficacy. Leveraging i...
Triplet–triplet annihilation photon upconversion (TTA-UC) is a process able to repackage two low-frequency photons into light of higher energy. This transformation is typically orchestrated by the electronic degrees of freedom within organic compounds possessing suitable singlet and triplet energies and electronic couplings. In this work, we propos...
Two-dimensional graphitic carbon nitride (GCN) is a popular metal-free polymer for sustainable energy applications due to its unique structure and semiconductor properties. Dopants and defects are used to tune GCN,...
3,4‐Dimethylenecyclobutene (DMCB) is an unusual isomer of benzene. Motivated by recent synthetic progress to substituted derivatives of this scaffold, we carried out a theoretical and computational analysis with a particular focus on the extent of (anti)aromatic character in the lowest excited states of different multiplicities. We found that the p...
In recent years, single atom catalysts have been at the forefront of energy conversion research, particularly in the field of catalysis. Carbon nitrides offer great potential as hosts for stabilizing metal atoms due to their unique electronic structure. We use ab initio nonadiabatic molecular dynamics to study photoexcitation dynamics in single ato...
Molecular symmetry controlling NLO-response directionality.
External pressure alters the nature of the emissive state of piezoluminescent pyridylvinylanthracene crystals.
A new family of molecules obtained by coupling Tröger’s base unit with dicyanovinylene-terminated oligothiophenes of different lengths has been synthesized and characterized by steady-state stationary and transient time-resolved spectroscopies. Quantum chemical calculations allow us to interpret and recognize the properties of the stationary excite...
On-surface synthesis has paved the way toward the fabrication and characterization of conjugated carbon-based molecular materials that exhibit π-magnetism such as triangulenes. Aza-triangulene, a nitrogen-substituted derivative, was recently shown to display rich on-surface chemistry, offering an ideal platform to investigate structure−property rel...
In this work, we introduce a novel hybrid approach, termed WFT-soDFT, designed to seamlessly incorporate DFT correlation into wavefunction ansatzes. This is achieved through a partitioning of the orbital space, distinguishing between large and small natural occupation numbers (NOONs) associated with wavefunction theory (WFT) and DFT correlation, re...
Nonadiabatic molecular dynamics provides essential insights into excited-state processes, but it is computationally intense and simplifications are needed. The classical path approximation provides critical savings. Still, long heating and equilibration steps are required. We demonstrate that practical results can be obtained with short, partially...
Triangulenes are a class of open‐shell triangular graphene flakes with total spin increasing with their size. In the last years, on‐surface‐synthesis strategies have permitted fabricating and engineering triangulenes of various sizes and structures with atomic precision. However, direct proof of the increasing total spin with their size remains elu...
Molecular photoswitches undergo a structural transformation upon excitation with light to intraconvert between two or more stable forms. In some cases, the structural rearrangement involves a cyclization reaction, that is, the transition between ring-open and ring-closed molecular forms. In this work we develop simple guidelines for the design of o...
Triangulenes are open‐shell triangular graphene flakes with total spin increasing with their size. In the last years, onsurface‐ synthesis strategies have permitted fabricating and engineering triangulenes of various sizes and structures with atomic precision. However, direct proof of the increasing total spin with their size remains elusive. In th...
A combined experimental and theoretical study focused on the elucidation of the polymerization mechanism of the crystal monomer to crystal polymer reaction of a bisindenedione compound in the solid state. The experimental description and characterization of the polymer product have been reported elsewhere and, in this article, we address the first...
Molecules present a versatile platform for quantum information science1,2 and are candidates for sensing and computation applications3,4. Robust spin-optical interfaces are key to harnessing the quantum resources of materials⁵. To date, carbon-based candidates have been non-luminescent6,7, which prevents optical readout via emission. Here we report...
The development of luminescent organic radicals has resulted in materials with excellent optical properties for near-infrared (NIR) emission. Applications of light generation in this range span from bioimaging to surveillance. Whilst the unpaired electron arrangements of radicals enable efficient radiative transitions within the doublet-spin manifo...
A combined experimental and theoretical study focused on the elucidation of the polymerization mechanism of crystal monomer to crystal polymer reaction of a bisindacene compound in the solid state has been carried out. The experimental description and characterization of the polymer product have been reported elsewhere and, in this article, we addr...
In this work, we focus on the understanding of the driving force behind the S1-T1 excited-state energy inversion (which would thus violate Hund's rule, making the S1 state lower in energy than the T1 state) of two non-benzenoid non-alternant hydrocarbons, composed of odd-membered rings. The molecules considered here have identical chemical composit...
Triangulenes are open-shell triangular graphene flakes with total spin increasing with their size. In the last years, on-surface-synthesis strategies have permitted fabricating and engineering triangulenes of various sizes and structures with atomic precision. However, direct proof of the increasing total spin with their size remains elusive. In th...
The violation of the Kasha photoemission rule in organic molecules has intrigued chemists since their discovery, being always of relevance given its connection with unique electronic properties of molecules. However, an understanding of the molecular structure-anti-Kasha property relationship in organic materials has not been well-established, poss...
The development of functional organic molecules requires structures of increasing size and complexity, which are typically obtained by the covalent coupling of smaller building blocks. Herein, with the aid of high-resolution scanning tunneling microscopy/spectroscopy and density functional theory, the coupling of a sterically demanded pentacene der...
Photoacids are molecules which become (more) acidic under photoirradiation, and they find valuable applications in organic synthesis and biological chemistry. We herein report a new photoacid, HDMAPAN-(BF4)2, which functions by a different photoacidity mechanism than existing ones. HDMAPAN-(BF4)2, consisting of one dibenzotropylium and one aniliniu...
Molecules present a versatile platform for quantum information science, and are candidates for sensing and computation applications. Robust spin-optical interfaces are key to harnessing the quantum resources of materials. To date, carbon-based candidates have been non-luminescent, which prevents optical read-out. Here we report the first organic mo...
A polycyclic conjugated hydrocarbon (PCH1) containing four contiguous heptagons was synthesized by Juan Casado, Junzhi Liu et al. in their Communication (DOI: 10.1002/anie.202217124). The four contiguous heptagons form a Z shape in the central π‐electron skeleton, giving PCH1 a butterfly‐shaped conformation.
A polycyclic conjugated hydrocarbon (PCH1) containing four contiguous heptagons was synthesized by Juan Casado, Junzhi Liu et al. in their Communication (DOI: 10.1002/anie.202217124). The four contiguous heptagons form a Z shape in the central π‐electron skeleton, giving PCH1 a butterfly‐shaped conformation.
In this work we perform electronic structure calculations to unravel the origin of spin-orbit couplings (SOCs) in open-shell molecules. For that, we select systems displaying di or polyradical character, e.g., trimethylene, and analyze the changes in the magnitude of SOC constants along molecular distortions of ethylene and in the presence of inter...
Incorporating non‐hexagonal rings into polycyclic conjugated hydrocarbons (PCHs) can significantly affect their electronic and optoelectronic properties and chemical reactivities. Here, we report the first bottom‐up synthesis of a dicyclohepta[a,g]heptalene‐embedded PCH (1) with four continuous heptagons, which are arranged in a “Z” shape. Compared...
Intermolecular interactions modulate the electro-optical properties of molecular materials and the nature of low-lying exciton states. Molecular materials composed by oligoacenes are extensively investigated for their semiconducting and optoelectronic properties. Here, we analyze the exciton states derived from time-dependent density functional the...
Incorporating the non‐hexagonal rings into polycyclic conjugated hydrocarbons (PCHs) can significantly affect their electronic and optoelectronic properties and chemical reactivities. Here, we report the first bottom‐up synthesis of a dicyclohepta[a,g]heptalene‐embedded PCH (1) with four continuous heptagons, which are arranged in a “Z” shape. Comp...
The search for efficient heavy atom free photosensitizers (PSs) for photodynamic therapy (PDT) is a very active field. We describe herein a simple and easily accessible molecular design based on the attachment of an enamine group as an electron-donor moiety at the meso position of the BODIPY core with different alkylation patterns. The effect of th...
Excited state aromaticity is a stimulating area of research, widely used as a probe to describe and rationalize many photochemical phenomena. Herein we review some of the recent findings of unprecedented aromatic stabilization in spin singlet excimer and through‐space aromatic character in triplet excimers of a series of linear [n]acenes, as paramo...
We describe the synthesis and spectroscopic study of the bichromophoric molecule DA-meso consisting of two boron difluoride curcuminoid (BF2-curcuminoid) units tethered by the rigid diacetylenic bridge. This structural feature imparts the quadrupolar-like DA-meso with a strong ability to self-assemble in solution, which induces a profound change in...
Metal halide perovskites (MHPs) have gained considerable attention due to their excellent optoelectronic performance, which is often attributed to unusual defect properties. We demonstrate that midgap defect levels can exhibit very large and slow energy fluctuations associated with anharmonic acoustic motions. Therefore, care should be taken classi...
Thermally activated delayed fluorescence (TADF) is an upconversion photophysical process based on the population of a bright excited singlet state from an excited triplet via reverse intersystem crossing (rISC), which might be employed to overcome the statistical limitation of electron‐hole recombination in organic light‐emitting diodes. In this wo...
Polaritons are unique hybrid light-matter states that offer an alternative way to manipulate chemical processes. In this work, we show that singlet fission dynamics can be accelerated under strong light-matter coupling. For superexchange-mediated singlet fission, state mixing speeds up the dynamics in cavities when the lower polariton is close in e...
Nitrogen heteroatom doping into a triangulene molecule allows tuning its magnetic state. However, the synthesis of the nitrogen-doped triangulene (aza-triangulene) has been challenging. Herein, we report the successful synthesis of aza-triangulene on the Au(111) and Ag(111) surfaces, along with their characterizations by scanning tunneling microsco...
Generation of triplet states in assemblies of organic chromophores is extremely appealing for their potential use in optoelectronic applications. In this work, we investigate the intricacies of triplet state generation in an orthogonal BODIPY dimer by combining delayed photoemission techniques with electronic structure calculations. Our analysis pr...
The modulation of intermolecular interactions upon aggregation induces changes in excited state properties of organic molecules that can be detrimental for some optoelectronic applications but can be exploited for others. The time-dependent density functional theory (TDDFT) is a cost-effective approach to determining the exciton states of molecular...
Exciton transport in molecular materials is usually well described by the Fermi Golden Rule within the Condon approximation. However, when collective or molecular vibrations are thermally accesible, dynamic disorder effects have a sizable impact on the predicted exciton transfer rates, and need to be considered for quantitative evaluation. In this...
Neutral organic radical emitters are promising alternative candidates for efficient OLEDs. Their potential relies on the ability to avoid spin statistics losses of charge recombination as in closed-shell emitters. Yet,...
An intersystem crossing (ISC) rate constant of 1.0×10¹¹ s⁻¹ was previously registered with a spiro‐bis‐benzophenone scaffold. Triplet generation efficiency could be further enhanced by stabilizing the spiro‐charge‐transfer (CT) state and rationally designing spiro‐compounds (SCTs) that consist of electron‐rich diphenyl ether as the spiro‐CT donor a...
Nitrogen heteroatom doping into a triangulene molecule allows tuning its magnetic state. However, the synthesis of the nitrogen-doped triangulene (aza-triangulene) has been challenging. Herein, we report the successful synthesis of aza-triangulene on the Au(111) and Ag(111) surfaces, along with their characterizations by scanning tunneling microsco...
Engineering a low singlet-triplet energy gap (ΔEST) is necessary for efficient reverse intersystem crossing (rISC) in delayed fluorescence (DF) organic semiconductors but results in a small radiative rate that limits performance in LEDs. Here, we study a model DF material, BF2, that exhibits a strong optical absorption (absorption coefficient = 3.8...
Spiro‐linked bichromophoric molecular systems are superior for triplet excited state generation. First, the two chromophores are tethered into a close proximity not accessible via alternative linkage, promoting spiro‐conjugation mediated charge‐transfer (CT). Second, the spiro‐orthogonality inhibit FRET‐type non‐radiative deactivation and high rigi...
Polaritons are unique hybrid light-matter states that offer an alternative way to manipulate chemical processes and change material properties. In this work we theoretically demonstrate that singlet fission dynamics can be accelerated under strong light-matter coupling. For superexchange-mediated singlet fission, state mixing speeds up the dynamics...
A prerequisite to characterize magnetic materials is the capability to describe systems containing unpaired electrons. In this study, we benchmark the one-shot GW (G 0 W 0) on top of different unrestricted mean-field solutions for open-shell molecules using Dunning’s correlation-consistent basis sets expanded in terms of Gaussian functions. We find...
This article summarizes technical advances contained in the fifth major release of the Q-Chem quantum chemistry program package, covering developments since 2015. A comprehensive library of exchange–correlation functionals, along with a suite of correlated many-body methods, continues to be a hallmark of the Q-Chem software. The many-body methods i...
Thermally activated delayed fluorescence (TADF) and room temperature phosphorescence (RTP) are two photophysical phenomena which utilize triplet excitons. In this work, we demonstrate how variation of the anion in organic salts with carbazole and phenothiazine-5,5-dioxide donors and pyridinium and quinolinium acceptors may be used to switch between...
In this review we outline the theory and recent progress of the restricted active space configuration interaction (RASCI) methodology within the hole and particle approximation. The RASCI is a single reference approach based on the splitting of the orbital space in different subsets, in which the target CI space is expressed by the concomitant numb...
A new compound (1) formed by two antiparallelly disposed tetracyano thienoquinoidal units has been synthesized and studied by electrochemistry, UV/Vis‐NIR, IR, EPR, and transient spectroscopy. Self‐assembly of 1 on a Au(111) surface has been investigated by scanning tunneling microscopy. Experiments have been rationalized by quantum chemical calcul...
Engineering a low singlet-triplet energy gap ({\Delta}EST) is necessary for efficient reverse intersystem crossing (rISC) in delayed fluorescence (DF) organic semiconductors, but results in a small radiative rate that limits performance in LEDs. Here, we study a model DF material, BF2, that exhibits a strong optical absorption (absorption coefficie...
This article describes the enhanced sensitivity to a viscous medium by a molecular rotor based fluorophore (RBF), TPSI I. The TPSI I molecule is designed in such a way that it consists of a rotor and a fluorophore with a π-rich bridge between them. TPSI I is a light-responsive material in solution as well as in the solid state. The structural desig...
A new compound formed by two antiparallelly disposed tetracyano thienoquinoidal units is synthesized. Such species features an in-plane to out-of-plane switch of the electric dipole momentum upon adsorption and self-assembly on Au(111).
Abstract
A new compound (1) formed by two antiparallelly disposed tetracyano thienoquinoidal units has been synt...
Electronic structure methods emerging from the combination of multiconfigurational wave functions and density functional theory (DFT) aim to take advantage of the strengths of the two nearly antagonistic theories. One of the common strategies employed to merge wave function theory (WFT) with DFT relies on the range separation of the Coulomb operato...
Pro‐aromatic molecules have higher‐energy diradicaloid states that are significantly influenced by resonance structures in which conjugated rings take on Hückel‐aromatic character. Recently, it has been argued that there are also pro‐aromatic molecules that adopt central units with 4nπ‐electron Baird‐aromatic character in the T1 state, although det...
Pro‐aromatic molecules have higher‐energy diradicaloid states that are significantly influenced by resonance structures in which conjugated rings take on Hückel‐aromatic character. Recently, it has been argued that there are also pro‐aromatic molecules that adopt central units with 4 n π‐electron Baird‐aromatic character in the T 1 state, although...
The ultimate goal for singlet fission is that each photo-excited singlet exciton, S1, will result in two triplet excitons with unity yield. However, the singlet fission is now recognized to be complicated, involving bright/dark excited states of different spin multiplicity. Identifying the role of such states is vital to optimize singlet fission yi...
p>The present study aims to provide a solid ground for the identification, characterization and controlled design of pro-aromatic quinoidal organic compounds holding conjugated rings with Hückel and/or Baird (singlet and triplet) excited state aromatic character, and expects to become a reference work for future studies on Baird-aromaticity. Concre...