Daniel Roca-Sanjuán

University of Valencia | UV · Instituto de Ciencia Molecular (ICMol)

In this article the recent developments of the open-source OpenMolcas chemistry software environment, since spring 2020, are described, with the main focus on novel functionalities that are accessible in the stable branch of the package and/or via interfaces with other packages. These community developments span a wide range of topics in computatio...

Excited-state absorption (ESA) spectra of π-conjugated compounds are frequently calculated by (quadratic response) time-dependent density functional theory, (QR) TD-DFT, often giving a reasonable representation of the experimental results despite the (known) incomplete electronic description. To investigate whether this is inherent to the method, w...

Polysulfur species have been proposed to be the unknown near-UV absorber in the atmosphere of Venus. Recent work argues that photolysis of one of the (SO)2 isomers, cis-OSSO, directly yields S2 with a branching ratio of about 10%. If correct, this pathway dominates polysulfur formation by several orders of magnitude, and by addition reactions yield...

Mercury, a global contaminant, enters the stratosphere through convective uplift, but its chemical cycling in the stratosphere is unknown. We report the first model of stratospheric mercury chemistry based on a novel photosensitized oxidation mechanism. We find two very distinct Hg chemical regimes in the stratosphere: in the upper stratosphere, ab...

Sulfur trioxide is a critical intermediate for the sulfur cycle and the formation of sulfuric acid in the atmosphere. The traditional view is that sulfur trioxide is removed by water vapor in the troposphere. However, the concentration of water vapor decreases significantly with increasing altitude, leading to longer atmospheric lifetimes of sulfur...

The theoretical prediction of molecular electronic spectra by means of quantum mechanical (QM) computations is fundamental to gain a deep insight into many photophysical and photochemical processes. A computational strategy that is attracting significant attention is the so-called Nuclear Ensemble Approach (NEA), that relies on generating a represe...

Until now, surface-deposited stilbenes have been much less studied than other photochromic systems. Here, an asymmetrically substituted styrene incorporating a redox-active ferrocene moiety and a terminal alkyne group has been synthesised to investigate its photoisomerization in solution, and upon the formation of chemisorbed self-assembled monolay...

State-of-the-art CASSCF/CASPT2 calculations are used to investigate the role of double excitations on the ground (GSA) and excited state absorption (ESA) spectra of distyrylbenzene (DSB), an important prototype medium-sized p-conjugated organic compound for optoelectronics. The multi-reference results are compared with linear and quadratic response...

Cobaltabis(dicarbollide) anion ([ o ‐COSAN] ‐ ) is a well‐known metallacarborane with multiple applications in a variety of fields. In aqueous solution, the cisoid rotamer is the most stable disposition in the ground state. The present work provides theoretical evidence on the possibility to photoinduce the rotation from the cisoid to the transoid...

Cobaltabis(dicarbollide) anion ([ o ‐COSAN] ‐ ) is a well‐known metallacarborane with multiple applications in a variety of fields. In aqueous solution, the cisoid rotamer is the most stable disposition in the ground state. The present work provides theoretical evidence on the possibility to photoinduce the rotation from the cisoid to the transoid...

Hydroxysulfinyl radical (HOSO) is important due to its involvement in climate geoengineering upon SO2 injection and generation of the highly hygroscopic H2SO4. Its photochemical behavior in the upper atmosphere is, however, uncertain. Here we present the ultraviolet-visible photochemistry and photodynamics of this species by simulating the atmosphe...

Photocycloreversion plays a central role in the study of the repair of DNA lesions, reverting them into the original pyrimidine nucleobases. Particularly, among the proposed mechanisms for the repair of DNA (6-4) photoproducts by photolyases, it has been suggested that it takes place through an intermediate characterized by a four-membered heterocy...

Luminescent small, all‐organic molecules are of tremendous interest in materials and life science applications. Nevertheless, targeted design requires a basic understanding of the excited state deactivation pathways of the molecules themselves, and the modulations of the processes that occur in the solid state. This particularly concerns crystallin...

We present the first examples of alkylated derivatives of the macropolyhedral boron hydride, anti-B18H22, which is the gain medium in the first borane laser. This new series of ten highly stable and colorless organic-inorganic hybrid clusters are capable of the conversion of UVA irradiation to blue light with fluorescence quantum yields of unity. T...

Luminol is a popular molecule that is currently gaining further interest due to its potential role for non-invasive cancer treatments. Design of more efficient derivatives in this context would benefit from a clear knowledge on the origin of the distinct intensity and spectroscopic properties in protic and aprotic solvents observed experimentally,...

Recent progress (2018–2019) in the field of quantum chemistry applied to the excited electronic state are presented in this book chapter. General developments of methods and theory are described first, followed by applications organised in three main topics, (i) photo-induced chemistry (photochemistry), (ii) chemically induced light emission (chemi...

Significance The atmospheric chemistry of mercury, a global priority pollutant, is key to its transport and deposition to the surface environment. Assessments of its risks to humans and ecosystems rely on an accurate understanding of global mercury cycling. This work shows that the chemical reactions and rates currently employed to interpret Hg che...

The photoinduced cycloreversion of oxetanes has been thoroughly investigated in connection with the photorepair of the well-known DNA (6-4) photoproducts. In the present work, the direct photolysis of the two regioisomers arising from irradiation of benzophenone (BP) and 1,3-dimethylthymine (DMT), namely the head-to-head (HH-1) and head-to-tail (HT...

In the search for innovative new light sources, the discovery that solutions of the boron hydride anti-B18H22 generate photostable blue laser emission stands out in its significance as the first laser borane. Surprisingly, though, the laser performance of anti-B18H22 (~10 % efficiency) does not match the expectations based on its exceptional photop...

Lapatinib (LAP) is an anticancer drug, which is metabolized to the N‐ and O‐dealkylated products (N‐LAP and O‐LAP, respectively). In view of the photosensitizing potential of related drugs, a complete experimental and theoretical study has been performed on LAP, N‐LAP and O‐LAP, both in solution and upon complexation with human serum albumin (HSA)....

Mercury is a contaminant of global concern that is transported throughout the atmosphere as elemental mercury Hg(0) and its oxidized forms Hg(I) and Hg(II). The efficient gas phase photolysis of Hg(II) and Hg(I) has recently been reported. However, whether the photolysis of Hg(II) leads to other stable Hg(II) species, to Hg(I), or to Hg(0) and its...

Mercury is a contaminant of global concern that is transported throughout the atmosphere as elemental mercury Hg(0) and its oxidized forms Hg(I) and Hg(II). The efficient gas phase photolysis of Hg(II) and Hg(I) has recently been reported. However, whether the photolysis of Hg(II) leads to other stable Hg(II) species, to Hg(I), or to Hg(0) and its...

In humans, vision is limited to a fraction of the electromagnetic spectrum. One possible strategy for enhancing vision in deep-red or poor-light conditions consists in recruiting chlorophyll derivatives in the rod photoreceptors of the eye, as suggested in some deep-sea fish. Here, we employ all-atom molecular simulations and high-level quantum che...

Photoswitchable molecules have attracted wide interest for many applications in chemistry, physics, and materials science. In this work, we revisit the reversible photochemical and thermal rearrangements of the two B20H18²⁻ isomers reported by Hawthorne and Pilling in 1966, whose mechanism had not been understood so far. We investigate the rearrang...

In the framework of optoelectronic luminescent materials, non-radiative decay mechanisms are relevant to interpret efficiency losses. These radiationless processes are herein studied theoretically for a series of stilbenoid derivatives, including distyrylbenzene (DSB) and cyano-substituted distyrylbenzene (DCS) molecules in vacuo. Given the difficu...

Treatment of the laser borane anti-B18H22 (compound 1) with iodine in ethanol gives the monoiodinated derivative 7-I-anti-B18H21 (compound 2) in 67% yield, or, by reaction with iodine or ICl in the presence of AlCl3 in dichloromethane, the diiodinated derivative 4,4'-I2-anti-B18H20 (compound 3) in 85% yield. On excitation with 360 nm light, both co...

Decaborane(14), nido-B10H14, is the major commercially available molecular building block in boron cluster chemistry. The condensation of two such {nido-B10} blocks gives the known isomers of B18H22 – a molecule used in the fabrication of p-type semiconductors and capable of blue laser emission. Here, we computationally determine the structures and...

The efficient gas-phase photoreduction of Hg(II) has recently been shown to significantly change mercury cycling in the atmosphere and its deposition to the Earth´s surface. However, the photochemistry of key Hg(I) species within that cycle is currently not considered. Here we present UV-Vis absorption spectra and cross sections of HgCl, HgBr, HgI,...

Oxidative damage can compromise the biological function of DNA/RNA nucleobases. Among the several agents that can cause oxidative damage in cells, hydroxyl radical (•OH) is considered one of the most reactive species able to add at either the C5 or C6 positions of the C5=C6 double bond of pyrimidine nucleobases. The present work tackles, firstly, t...

A data survey on experimental fluorescence quantum yields of (multi)substituted dicyano-distyrylbenzenes in fluid solution evidences that non-radiative decay increases with the Franck-Condon energy (EFC), being opposite to the conventional energy gap law. Quantum-chemistry indicates that this is controlled by access to the conical intersection (CI)...

Quantum‐chemistry determinations of the luminol chemiluminescence mechanism have made it possible to: first, clarify the spin inversion of the reaction; secondly, to determine the concerted nature of the two steps of 3O2 addition and 1N2 elimination; thirdly, to answer why such oxygen by nitrogen substitution must occur for an efficient excited‐sta...

Light emission of luminol is probably one of the most popular chemiluminescence reactions due to its use in forensic science, recently displaying promising applications on the treatment of cancer in deep tissues. The mechanism is however very complex and distinct possibilities have been proposed. By efficiently combining DFT and CASPT2 methodologie...

The electronic–structure properties of the low–lying electronic states and the absorption cross sections of mercury halides HgCl2, HgBr2, HgI2, HgBrCl, HgClI, and HgBrI have been determined within the UV–Vis spectrum range (170 nm ≤ λphoton ≤ 600 nm) by means of the complete–active–space self–consistent field/multi–state complete–active–space secon...

Anthropogenic mercury (Hg(0)) emissions oxidize to gaseous Hg(II) compounds, before deposition to Earth surface ecosystems. Atmospheric reduction of Hg(II) competes with deposition, thereby modifying the magnitude and pattern of Hg deposition. Global Hg models have postulated that Hg(II) reduction in the atmosphere occurs through aqueous-phase phot...

The intrinsic photostability of nucleic acids is intimately related to life evolution, while its understanding at the molecular and electronic levels remains a challenge for modern science. Among the different decay pathways proposed in the last two decades, the excited-state hydrogen transfer between guanine-cytosine base pairs has been identified...

Advances (2016–2017) in Quantum Chemistry of the Excited State (QCEX) are presented in this book chapter focusing firstly on developments of methodology and excited-state reaction-path computational strategies and secondly on the applications of QCEX to study light–matter interaction in distinct fields of biology, (nano)-technology, medicine and th...

Azetidines are interesting compounds in medicine and chemistry as bioactive scaffolds but also as synthetic intermediates. However, the photochemical processes involved in the generation and fate of azetidine‐derived radical ions have been scarcely reported. In this context, the photoreduction of this four‐membered heterocycle might be relevant in...

Bioluminescence is a phenomenon that has fascinated mankind for centuries. Today the phenomenon and its sibling, chemiluminescence, have impacted society with a number of useful applications in fields like analytical chemistry and medicine, just to mention two. In this review, a molecular-orbital perspective is adopted to explain the chemistry behi...

Reaction of anti -B 18 H 221 with pyridine in neutral solvents gives sparingly soluble B 16 H 18 -3′,8′-Py 23a as the major product (ca. 53 %) and B 18 H 20 -6′,9′-Py 22 (ca. 15 %) as the minor...

Solid state luminescence enhancement (SLE) of conjugated organic materials has found great impact in materials science, but a deep understanding is rather limited by now. Here, we investigate a prototype example of SLE materials, cyano-substituted distyrylbenzene (DCS) with varying systematically and subtly the substitution pattern (inter alia of t...

Oxidation of nucleic acids are ubiquitous in living beings under metabolic impairments and/or exposed to external agents such as radiation, pollutants, or drugs, playing a central role in the development of many diseases mediated by DNA/RNA degeneration. Great efforts have been devoted to unveil the molecular mechanisms behind the OH radical additi...

Chemiluminescence is a fundamental process of chemistry consisting in the conversion of chemical energy stored in chemical bonds into light. It is used by nature and by man-made technology, being especially relevant in chemical analysis. The understanding of the phenomenon strongly relies in the study of peroxide models such as 1,2-dioxetanones. In...

We report the ability of a chiral Cu(II) 3D MOF based on the tripeptide Gly-L-His-Gly (GHG) for the enantioselective separation of metamphetamine and ephedrine. Monte Carlo simulations suggest that chiral recognition is linked to preferential binding of one of the enantiomers as result of either stronger or additional H-bonds with the framework tha...

B18H20(NC5H5)2 is a rare example of two conjoined boron hydride subclusters of nido and arachno geometrical character. At room temperature, solutions of B18H20(NC5H5)2 emit a 690 nm fluorescence. In the solid state, this emission is shifted to 620 nm and intensifies due to restriction of the rotation of the pyridine ligands. In addition, there is a...

Almost all chemiluminescent and bioluminescent reactions involve cyclic peroxides. The structure of the peroxide and reaction conditions determine the quantum efficiency of light emission. Oxidizable fluorophores, the so-called activators, react with 1,2-dioxetanones promoting the former to their first singlet excited state. This transformation is...

The electronic states of atmospheric relevant molecules IBr and HgBr2 are reported, within the UV-Vis spectrum range (170 nm <= lambda(photon) <= 600 nm) by means of the complete-active-space self-consistent field/multi-state complete-active-space second-order perturbation theory/spin-orbit restricted-active-space state-interaction (CASSCF/MS-CASPT...

OH radical is a well-known mediator in the oxidation of biological structures like DNA. Over the last decades, the precise events taking place after reaction of DNA nucleobases with OH radical have been widely investigated by the scientific community. Thirty years after the proposal of the main routes for the reaction of .OH with adenine (A. Vieira...

The present study provides new insights into the topography of the potential energy hypersurfaces (PEHs) of the thymine nucleobase in order to rationalize its main ultrafast photochemical decay paths by employing two methodologies based on the complete active space self-consistent field (CASSCF) and the complete active space second-order perturbati...

Herein, we report complementary computational and experimental evidence supporting the existence, for indan-1-ylidene malononitrile and fluoren-9-ylidene malononitrile, of a non-radiative decay channel involving double bond isomerisation motion. The results of UV-Vis transient absorption spectroscopy highlight that the decay takes place within hund...

Recent advances (2014–2015) in computational photochemistry and chemiluminescence derive from the development of theory and from the application of state-of-the-art and new methodology to challenging electronic-structure problems. Method developments have mainly focused, first, on the improvement of approximate and cheap methods to provide a better...

Supplementary

The chemical fate of radical intermediates is relevant to understand the biological effects of radiation and to explain formation of DNA lesions. A direct approach to selectively generate the putative reactive intermediates is based on the irradiation of photolabile precursors. But, up to date, radical formation and reactivity have only been studie...

The decay channels of singlet excited adenine uracil monophosphate (ApU) in water are studied with CASPT2//CASSCF:MM potential energy calculations and simulation of the 2D-UV spectroscopic fingerprints with the aim of elucidating the role of the different electronic states of the stacked conformer in the excited state dynamics. The adenine (1) La s...

We report a computational investigation of the hydrogen abstraction (H-abstraction) induced by triplet benzophenone (3BP) on thymine nucleobase and backbone sugar. The chemical process is studied both using high level multiconfigurational perturbation and density functional theory. Both methods show a good agreement in predicting small kinetic barr...

The photochemistry of benzophenone, a paradigmatic organic molecule for photosensitization, was investigated by means of surface-hopping ab initio molecular dynamics. Different mechanisms were found to be relevant within the first 600 fs after excitation: the long-debated direct (S1→T1) and indirect (S1→T2→T1) mechanisms for population of the low-l...

Understanding the complex events that take place in nucleic acids upon UV light exposure constitutes a key step in the comprehension of life evolution, as well as in the determination of the mechanisms that can originate genetic mutations and lead to the development of diseases like skin cancer. Over the last decade, intra- and inter-strand process...

Low-energy (0-3 eV) ballistic electrons originated during the irradiation of biological material can interact with DNA/RNA nucleobases yielding transient-anion species which undergo decompositions. Since the discovery that these reactions can eventually lead to strand breaking of the DNA chains, great efforts have been dedicated to their study. The...

Excited-state chemistry is usually ascribed to photo-induced processes, such as fluorescence, phosphorescence, and photochemistry, or to bio- and chemiluminescence, in which light emission is originated by a chemical reaction. A third class of excited-state chemistry, however, is possible that promotes photochemical phenomena by chemienergizing cer...

Benzophenone, the parent of the diarylketone family, is a versatile compound commonly used as a UV blocker. It may also trigger triplet-based DNA photosensitization. Therefore, benzophenone is involved in DNA photodamage induction. In the absence of experimentally resolved structure, the mechanism of DNA damage production remains elusive. Employing...