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Photoinduced electron transfer is studied in a series of inclusion complexes of structurally modified phenine nanotubes (pNT) with C70 using the TD‐DFT method. Analysis of electronic properties of the complexes shows that the electron transfer is infeasible in pNT_4d⊃C70 built on the tetrameric array of [6]cyclo‐meta‐phenylene ([6]CMP) units. However, replacing one or more [6]CMP units with a coronene moiety enables electron transfer from pNT to C70. The generation of the charge separated states from the lowest locally excited states occurs on a sub‐nanosecond time scale. Depending on the number of the [6]CMP units, the charge recombination rate varies from 1.8 ⋅ 107 to 3.1 ⋅ 102 s−1, i. e., five orders of magnitude., Triggering electron transfer with coronene: The photoinduced electron transfer in complexes of phenine nanotube with C70 fullerene can be activated by replacing one or more [6]cyclo‐meta‐phenylene units in the nanotube with a coronene moiety. The number of vacancy defects strongly affects the rates of charge separation and recombination processes.

Investigation of photoinduced electron transfer (PET) in a series of experimentally reported complexes of fullerene with phosphangulene oxides shows that the replacement of O atoms in the bridge of phosphangulene with S atoms promotes efficient and ultrafast ET from fullerene to phosphangulene oxide in PGOOSS⊃C60 and PGOSSS⊃C60 complexes. The results obtained can be useful in development of photovoltaic devices based on phosphangulenes We are grateful for financial support from the Spanish MINECO (Network RED2018-102815-T, project CTQ2017‐85341‐P, and Juan de la Cierva contract IJC2019-039846-I to A.J.S. and FJCI‐2017‐32757 to O.A.S.) and the Catalan DIUE (2017SGR39)

The shift towards renewable energy is one of the main challenges of this generation. Dye-sensitized solar cells (DSSC), based on donor-acceptor architectures, can help on this transition as they present excellent photovoltaic efficiencies yet cheap and simple manufacturing. For molecular heterojunctions DSSCs, donor-acceptor pairs are linked in a covalent manner, which facilitates their tailoring and rational design. Nevertheless, reliable computational characterization of charge transfer rate constants (kCT) is needed to speed this development process up. In this context, the performance of time-dependent density functional theory for the calculation of kCT's in donor-acceptor fullerene-based dyads has not been benchmarked yet. Herein, we present a detailed analysis on the performance of seven well-known density functional approximations (DFAs) for this type of systems, focusing on several parameters as the reorganization energies (λ), electronic couplings (VDA), and Gibbs energies (ΔG^0_CT), as well as in the final rate constants. The amount of exact exchange at short range (SR) and long range (LR) electron-electron distances (and the transition from SR to LR) turned out to be key for the success of the prediction. The tuning of these parameters improves significantly the performance of current DFAs This work was supported with funds from the Ministerio de Economía y Competitividad (MINECO) of Spain (project CTQ2017- 85341-P to M.S. and A.A.V.), the Spanish government MICINN (project PGC2018-098212-B-C22 to J.M.L), and the Generalitat de Catalunya (project 2017SGR39 to M.S. and J.M.L.). We thank the Spanish government for the predoctoral grant to P.B.-S. (FPU17/02058)

Perfluorocycloparaphenylenes (PFCPPs) are cycloparaphenylenes (CPPs) in which all hydrogen atoms have been replaced by fluorine atoms. Like CPPs, PFCPPs are highly strained, hoop-shaped π-conjugated molecules. In this article, we report a computational modeling of photoinduced electron transfer processes in the inclusion complex of PF[10]CPP with C

Functionalization of nanotubes with donor and acceptor partners by the Bingel reaction leads to formation of charge-transfer dyads, which can operate in organic photovoltaic devices. In this work, we theoretically examine the mechanism of the Bingel reaction for (6,5)-chiral, (5,5)-armchair, and (9,0)-zig-zag single-walled carbon nanotubes (SWCNTs), and demonstrate that the reaction is regioselective and takes place at the perpendicular position of (6,5)- and (5,5)-SWCNTs, and oblique position of (9,0)-SWCNT. Further, we design computationally the donor-acceptor complexes based on (6,5)-SWCNT coupled with partners of different electronic nature. Analysis of their excited states reveals that efficient photoinduced charge transfer can be achieved in the complexes with exTTF, ZnTPP, and TCAQ. The solvent can significantly affect the population of the charge separated states. Our calculations show that electron transfer (ET) occurs in normal Marcus regime on sub-nanosecond time scale in the complexes with exTTF and ZnTPP, and in inverted Marcus regime on picosecond time scale in the case of TCAQ derivative. The ET rate is found to be not very sensitive to the degree of functionalization of the nanotube We are grateful for financial support from the Spanish MINECO (project CTQ2017‐85341‐P and Juan de la Cierva formación contracts FJCI‐2016‐29448 to A.J.S. and FJCI‐2017‐32757 to O.A.S.), and the Catalan DIUE (2017SGR39). O.A.S and M.S thankfully acknowledge the computer resources at MareNostrum and the technical support provided by Barcelona Supercomputing Center (RES-QS-2019-2-0016)

In this work, we computationally study the photoinduced electron transfer in fullerene inclusion complexes of two phenine nanotubes pre-pNT⊃C70 and pNT⊃C70 and their nanographene analog [4]CHBC⊃C70. Charge separation is shown to efficiently occur in [4]CHBC⊃C70. In contrast, the electron transfer process between the host and guest units in the pre-pNT⊃C70 and pNT⊃C70 complexes is blocked by the structural changes incorporated in the nanographene framework.

The formation of supramolecular complexes between C60 and a molecular nanographene endowed with both positive and negative curvatures is described. The presence of a corannulene moiety and the saddle shape of the molecular nanographene allows the formation of complexes with 1:1, 1:2, and 2:1 stoichiometries. The association constants for the three possible supramolecular complexes were determined by 1H NMR titration. Furthermore, the stability of the three complexes was calculated by theoretical methods that also predict the photoinduced electron transfer from the curved nanographene to the electron acceptor C60. Time-resolved transient absorption measurements on the ns-time scale showed that the addition of C60 to NG-1 solutions and photo-exciting them at 460 nm leads to the solvent-dependent formation of new species, in particular the formation of the one-electron reduced form of C60 in benzonitrile was observed Ministerio de Ciencia, Innovación y Universidades. Grant Numbers: CTQ2017-83531-R, RED2018-102815-T, CTQ2017-85341-P, PID2020-113711GB-I00, CTQ2017-84327-P, IJC2019-039846-I Consell Català de Recerca i Innovació. Grant Number: 2017SGR39

Mechanically interlocked molecules (MIMs) attract significant attention of scientists over the past few decades due to their unusual architecture. For a long time, architectures of MIMs were represented by catenanes, rotaxanes, molecular knots, and their derivatives. Only several years ago, a new type of MIMs that do not possess interlocked rings or dumbbell shaped molecule threaded through a macroring was introduced. Suitanes – a class of MIMs, which consist of two separate components - contains a body with two or more rigid limbs protruding outwards and a close-fitting, all-in-one suit. We present the results of computational modelling of the photoinduced processes in the recently reported by F. Stoddart two-component MIM - suit[3]ane, and similar systems with aromatic 3-fold symmetric bodies.[1] The reported suit[3]ane contains a benzotrithiophene (BTT) derivative with three n-hexyl substituents (BTT-3C6 ) as a body and 3-fold symmetric pyridinium-based cage, namely HexaCage6+ (HC6+∙6PF6 - ), as a suit. Analysis of the ground state properties of the suit[3]anes show that low LUMO of HC6+∙6PF6 - and its ability to delocalize charge make this cage an efficient electron acceptor. The TDDFT calculations for a series of inclusion complexes (HC6+∙6PF6 - ⊃ XXX, where XXX are aromatic 3-fold symmetric bodies) revealed that the photoinduced electron transfer process is favorable not only for the complexes with strong donors, such as thiatruxene or benzotrithiophenes, but also for poor donors, such as benzotrifuran. The photoinduced charge separation in the studied complexes occurs on a picosecond time scale. The computations predicts very similar electronic properties not only for single unit of suit[3]ane but also for its aggregates. The high stability of suit[3]anes in combination with their photoinduced electron transfer properties makes this new class of interlocked molecules promising materials for photovoltaic applications.[2] References: [1] J. F. Stoddart et al., J. Am. Chem. Soc. 2020, 142, 20152. [2] A.J. Stasyuk et al., J. Mater. Chem. C, 2021, 9, 9436. Figure 1

The formation of supramolecular complexes between C

We have studied the photophysics of tetrafurylethene, an aggregation-induced emission luminogen with exceptionally short intramolecular O-O distances of 2.80 Å and a significant red-shifted morphochromism (27 nm) when going from the aggregate to the crystal. The short O-O distances, which are substantially smaller than the sum of the van der Waals radii (3.04 Å), are due to the fact that the oxygen atoms act as an electronic bridge connecting the furan rings on opposite ends of the central double bond, giving rise to a circular delocalization of the π-electron density across the rings. In the excited state the O-O distance is further reduced to 2.70 Å; the increased O-O interaction causes a narrowing of the HOMO-LUMO gap, resulting in the red morphochromism of the emission. Our results show the structural origin of the red-shifted emission lies in close O-O contacts, paving the way for understanding the clusteroluminescence of oxygen-rich non-conjugated systems that emit visible light.

Over the last years, carbon nano-onions (CNOs) have been in focus in material science research. Their red-shifted absorption allows utilizing CNOs as promising photosensitizers. We report here a systematic study of excited state properties of six double-layered Li+ doped fullerenes of Ih symmetry: [Li@C60@C240]+, [Li@C60@C540]+, [Li@C60@C960]+, [Li@C240@C540]+, [Li@C240@C960]+ and [Li@C540@C960]+. On the basis of TDDFT calculations, we show that the long-wave absorption by the Li+ doped species leads to charge transfer (CT) between the inner and the outer shells unlike their neutral double-layered precursors. The CT energy depends strongly on the size of the concentric fullerenes and it can easily be tuned by varying both the encapsulated metal ion and the size of the shells. Two types of low-lying excited states are identified (1) capacitor-like structures, as Li+@C60-@C240+, with alternating positive and negative charges, and (2) states, where the positive charge is delocalized over the outer shell, as in Li@C240@C540+. We suggest a simple expression to estimate the energy difference of these excited states and to predict the type of the lowest CT state in nested fullerenes. The effect of nature of the encapsulated ion on the charge transfer state energies is considered. The HOMO - LUMO transition energy is found to vary significantly when going from [Li@C60@C240]+ to [Li@C540@C960]+

The synthesis and characterization of a covalent all-fullerene C60-Lu3N@Ih-C80 electron donor-acceptor conjugate has been realized by sequential 1,3-dipolar cycloaddition reactions of azomethine ylides on Lu3N@Ih-C80 and C60. To the best of our knowledge, this is the first time that two fullerenes behaving as both electron donor (Lu3N@Ih-C80) and acceptor (C60) are forming an electroactive dumbbell. DFT calculations reveal up to 16 diastereomeric pairs, that is, 8 syn and 8 with anti orientation, being the anti-RSSS isomer the most stable. Spectroelectrochemical absorption and femtosecond transient absorption experiments support the notion that a C60 --Lu3N@Ih-C80 + charge-separated state is formed. Spin conversion of the singlet C60 --Lu3N@Ih-C80 + charge-separated state into the triplet C60 --Lu3N@Ih-C80 + charge-separated state is facilitated by the heavy atom affect stemming from the Lu3N-cluster and, in turn, slows down the charge recombination by one order of magnitude Financial support from the European Research Council (ERC320441-Chirallcarbon and the MINECO of Spain (Projects CTQ2017-83531-R, CTQ2017-85341-P, and CTQ2017-84327- P, network CTQ2016-81911-REDT, and Juan de la Cierva formación contracts FJCI-2016-29448 to A.J.S. and FJCI-2017- 32757 to O.A.S.) is acknowledged. This work was also funded by the Deutsche Forschungsgemeinschaft (DFG) via SFB 953 “Synthetic Carbon Allotropes”, the Catalan DIUE (2017SGR39, XRQTC, and ICREA Academia 2014 Award to M.S.), and the FEDER fund (UNGI10-4E-801)

In this work, we study computationally, using the DFT/TDDFT approach, the photoinduced electron transfer (PET) in CPP-based donor-acceptor supramolecules C60⊂[10]CPP and Li+@C60⊂[10]CPP. Based on the analysis of the excited states we find a system, Li+@C60⊂[10]CPP, which shows anomalous solvent effects, i.e., destabilization of charge separated states by polar medium We are grateful for financial support from the Spanish MINECO (Network CTQ2016-81911-REDT, project CTQ2017- 85341-P, and Juan de la Cierva formación contracts FJCI-2016-29448 to A. J. S. and FJCI-2017-32757 to O. A. S.), and the Catalan DIUE (2017SGR39, XRQTC, and ICREA Academia 2014 Award to M. S.)

Molecular arrays containing donor–acceptor sites and antenna molecules are promising candidates for organic photovoltaic devices. Photoinduced electron transfer (PET) in multi-chromophore systems is controlled by a subtle interplay of donor and acceptor properties and solvent effects. In the present study, we explore how PET of fullerene [C60]–Zn-porphyrin–BODIPY triads can be modulated by passing from non-polar to polar media. To this end we perform a computational study of this complex using the DFT/TDDFT method. We find that the stabilization energy of charge transfer states by a polar medium depends significantly on whether the BODIPY moiety acts as an electron donor or an electron acceptor. To understand this effect of the environment, a detailed analysis of the initial and final states of the ET reactions is performed. We show that additional deactivation channels of the porphyrin excited state may come into play as solvent polarity increases.

A simple, non-iterative method to estimate hydration free energies of neutral molecules, ESE, is developed. It requires only atomic charges computed for isolated species. To obtain the solvation free energy, the COSMO electrostatic term is supplemented by an extra correction that describes the cavitation energy, van der Waals and specific interactions. This term depends on atomic parameters that are adjusted using a reference dataset. Despite its simplicity, the ESE method provides accurate hydration energies with a mean absolute error below 1 kcal mol-1, superseding most accurate existing polarization continuum methods. We show that the proposed scheme can be directly extended to non-aqueous solutions.

The discovery of the GFP-type dye DFHBI that becomes fluorescent upon binding to an RNA aptamer, termed Spinach, led to the development of a variety of fluorogenic RNA systems that enable genetic encoding of living cells. In view of increasing interest in small RNA aptamers and the scarcity of their photophysical characterisation, this paper is a model study on Baby Spinach, a truncated Spinach aptamer with half its sequence. Fluorescence and fluorescence excitation spectra of DFHBI complexes of Spinach and Baby Spinach are known to be similar. Surprisingly, a significant divergence between absorption and fluorescence excitation spectra of the DFHBI/RNA complex was observed on conditions of saturation at large excess of RNA over DFHBI. Since absorption spectra were not reported for any Spinach-type aptamer, this effect is new. Quantitative modelling of the absorption spectrum based on competing dark and fluorescent binding sites could explain it. However, following reasoning of fluorescence lifetimes of bound DFHBI, femtosecond-fluorescence lifetime profiles would be more supportive of the notion that the abnormal absorption spectrum is largely caused by trans-isomers formed within the cis-bound DFHBI/RNA complex. Independent of the origin, the unexpected discrepancy between absorption and fluorescence excitation spectra allows for easily accessed screening and insight into the efficiency of a fluorogenic dye/RNA system. Nanyang Technological University National Research Foundation (NRF) Published version This research was supported by the Vietnam National Foundation for Science and Technology Development (NAFOSTED) under grant number 106.02-2018.11 (to Nguyen Thuan Dao), Nanyang Technological University grants to M.-E. Michel-Beyerle and to Anh Tuan Phan. Alexander Voityuk is grateful for financial support from the MINECO, Spanish Ministerio de Economía y Competitividad. This work was supported in part by the Singapore National Research Foundation under its Campus for Research Excellence and Technological Enterprise (CREATE) programme.

Suitanes, a new class of two-component mechanically interlocked systems, have recently been developed. In this work, we report a detailed study of photoinduced electron transfer processes in suit[3]anes consisting of a 3-fold symmetric pyridinium-based (HC6+∙6PF6-) cage and substituted benzotrithiophenes, as well as other polycyclic aromatic guests. Analysis of electronic properties of the complexes shows that electron transfer is favorable for complexes of HC6+∙6PF6- with strong donors, such as thiatruxene, benzotrithiophenes, and benzotrifuran. The photoinduced electron transfer for these complexes occurs on the picosecond time scale. On the contrary, electron transfer does not occur in complexes HC6+∙6PF6- with benzotristiazole and benzotrisoxazole. Our results open perspectives for the future design of mechanically interlocked systems for application in photovoltaic devices We are grateful for financial support from the Spanish MINECO (Network RED2018-102815-T, project CTQ2017‐85341‐P, and Juan de la Cierva contract IJC2019-039846-I to A.J.S. and FJCI‐2017‐32757 to O.A.S.) and the Catalan DIUE (2017SGR39)

The photoinduced electron transfer is studied computationally in several Saturn-shaped inclusion complexes of carbo-aromatic rings and C60 fullerene - C72⊃C60, C96⊃C60, C120⊃C60, and C168⊃C60. Analysis of their structural and electronic properties shows that the charge separation process is efficient in C120⊃C60 and C168⊃C60 where the host molecule resembles the conjugated [24]circulene unit. In contrast, the electron transfer is not feasible in the complexes of the oligophenylene-based rings C72⊃C60 and C96⊃C60.

We present an efficient method with adjustable parameters for calculating the hydration free energy of molecules and ions using the gas-phase geometry and atomic charges. In most cases, the method yields accurate results, with a mean absolute error for neutral molecules below 1 kcal mol-1 and for ions about 3 kcal mol-1. Overall, despite its simplicity, the proposed method shows the best performance among major computational approaches applied to estimate hydration free energies. The method requires as input Cartesian cordinates and CM5 atomic charges only, which are easily available from any DFT calculation, and yields the hydration energy in a matter of seconds for a medium-size molecule or ion.

A triquinoline cationic moiety (TQ⋅H+) has recently been designed as a novel molecular unit for supramolecular chemistry. In addition to some useful features, TQ⋅H+ has strong electron‐acceptor properties, which renders the molecular cation a unique element in nanochemistry. TQ⋅H+ is found to form complexes with coronene (COR) and cycloparaphenylene (CPP). In this work, we report a computational study of photoinduced electron transfer in supramolecular complexes TQ⋅H+‐COR, TQ⋅H+⊂[12]CPP and (TQ⋅H+‐COR)⊂[12]CPP. The electron‐transfer rates are estimated by using the semi‐classical approach. The results are compared with the data previously obtained for a structurally similar inclusion complex Li+@C60⊂[10]CPP. In particular, we found a red solvatochromic shift for charge‐shift bands in the TQ⋅H+‐complexes unlike a blueshift showed by Li+@C60⊂[10]CPP. This distinction is explored in terms of electronic and structural features of the systems We are grateful for financial support from the Spanish MINECO (Network RED2018-102815-T, project CTQ2017‐85341‐P, and Juan de la Cierva formación contracts FJCI‐2016‐29448 to A.J.S. and FJCI‐2017‐32757 to O.A.S.), and the Catalan DIUE (2017SGR39, XRQTC, and ICREA Academia 2014 Award to M.S.).

The recently synthesized C18 molecule demonstrates strong electron acceptor properties similar to C60. In this work, we study computationally the ground and excited state properties of C18 and its complexes with several electron-donating molecules. We demonstrate that a high amount of the exact (HF) exchange in the DFT functional leads to a polyynic structure of C18, in agreement with the experiment. We show that in complexes of C18 with electron donors, the lowest excited states are charge separated states formed by electron transfer to C18. This makes C18 the smallest all-carbon electron acceptor reported so far. Because C18 exhibits a larger internal reorganization energy compared to fullerene C60, the electron transfer reactions with relatively high driving force will be shifted from the inverted to the normal Marcus regime when replacing C60 by C18 We are grateful for financial support from the Spanish MINECO (Network RED2018-102815-T, project CTQ2017-85341-P, and Juan de la Cierva formacio´n contracts FJCI-2016-29448 to A. J. S. and FJCI-2017-32757 to O. A. S.) and the Catalan DIUE (2017SGR39, XRQTC, and ICREA Academia 2014 Award to M. S.)

Fullerene based molecular heterojunctions such as the [6,6]-pyrrolidine-C60 donor-acceptor conjugate containing triphenylamine (TPA) are potential materials for high-efficient dye-sensitized solar cells. In this work, we estimate the rate constants for the photoinduced charge separation and charge recombination processes in TPA-C60 using the unrestricted and time-dependent DFT methods. Different schemes are applied to evaluate excited state properties and electron transfer parameters (reorganization energies, electronic couplings, and Gibbs energies). The use of open-shell singlet or triplet states, several density functionals and continuum solvation models is discussed. Strengths and limitations of the computational approaches are highlighted. The present benchmark study provides an overview of the expected performance of DFT-based methodologies in the description of photoinduced charge transfer reactions in fullerene heterojunctions We are grateful for financial support from the Spanish Ministerio de Economía y Competitividad (MINECO) (Project CTQ2014-54306-P), the Catalan DIUE (Project 2014SGR931, ICREA Academia 2014 Award to MS, and Xarxa de Referència en Química Teòrica i Computacional), and the FEDER fund (UNGI10-4E-801). JPM acknowledges the Mexican National Council of Science and Technology (CONACYT) for his PhD fellowship (register/application number 217067/312543).

We present a theoretical model for long-range triplet excitation energy transfer in DNA sequences of alternating adenine-thymine steps. It consists of thermally induced hops through thymine bases. Intrastrand hops between thymines separated by an AT step are preferred to interstrand hops between thymines in consecutive steps. Our multi-step mechanism is consistent with recent results (L. Antusch, N. Gass and H.-A. Wagenknecht, Angew. Chem., Int. Ed., 2017, 56, 1385-1389) describing a shallow dependence of triplet sensitized DNA damage relative to the distance between the sensitizer and the reacting thymine-thymine pair Financial support from the Ministerio de Economı´a y Competitividad (MINECO), Spain (project CTQ2015-69363-P), the Departament d’Innovacio´, Universitats i Empresa (DIUE), Generalitat de Catalunya (Project 2014SGR1202) is gratefully acknowledged

We propose a new atomic-charge analysis, termed adjusted charge partitioning (ACP) scheme. To partition the molecular electronic density into atomic components, weighting factors cAr2n-2exp(-αAr) with atomic parameters cA and αA are used. Extensive numerical tests were performed for 540 molecules containing 17 main-group elements H, Li to F, Na to Cl, Br, and I. The estimated dipole moments and atomic charges are compared with the data provided by a large number of alternative atomic-charge schemes including the Mulliken, Löwdin, Hirshfeld, Hirshfeld Iterative, CM5, ESP, NPA, and QTAIM population analyses. These tests show that the resulting atomic charges are insensitive to basis sets used, chemically consistent and accurately reproduce experimental dipole moments.

Over the last years, carbon nano-onions (CNOs) have been in focus in material science research. Apart from its prospective use in solar cells, the number of potential applications of CNOs have grown in the last decades. Among them, we can mention their application in gas storage processes, solid lubrication, or heterogeneous catalysis, and also as electrode materials in capacitors, anode materials in lithium-ion batteries, catalyst support in fuel cells, or electro-optical devices. From the analysis of the polarizability of CNOs, it was concluded that CNOs behave as near perfect nanoscopic Faraday cages.[1] If CNOs behave as ideal Faraday cages, the reactivity of the C240 cage should be the same in Li+@C240 and Li+@C60@C240. In the first part of this work, we have analyzed the Diels-Alder reaction of cyclopentadiene to the free C240 cage and the C60@C240 CNO together with their Li+-doped counterparts using density functional theory (DFT). We find that in all cases the preferred cycloaddition is on bond [6,6] of type B of the C240 cage. From the comparison between the reactivity of Li+@C240 and Li+@C60@C240, we conclude that C60@C240 does not act as a perfect Faraday cage.[2] In the second part of this work, we perform a systematic study of excited state properties of six double-layered Li+ doped fullerenes of Ih symmetry: [Li@C60@C240]+, [Li@C60@C540]+, [Li@C60@C960]+, [Li@C240@C540]+, [Li@C240@C960]+ and [Li@C540@C960]+. On the basis of TDDFT calculations, we show that the long-wave absorption by the Li+ doped species leads to charge transfer (CT) between the inner and the outer shells unlike their neutral double-layered precursors. The CT energy depends strongly on the size of the concentric fullerenes and it can easily be tuned by varying both the encapsulated metal ion and the size of the shells. Two types of low-lying excited states are identified (1) capacitor-like structures, as Li+@C60 -@C240 +, with alternating positive and negative charges, and (2) states, where the positive charge is delocalized over the outer shell, as in Li@C240@C540 +.[3] References [1] R. R. Zope, J. Phys. B: At. Mol. Opt. Phys. 41 (2008) 41, 085101; [b] R. R. Zope, S. Bhusal, L. Basurto, T. Baruah and K. Jackson, J. Chem. Phys. 143 (2015) 084306. [2] A. J. Luque-Urrutia, A. Poater and M. Solà. Chem. Eur. J., 26 (2020) 804-808. [3] A. J. Stasyuk, O. A. Stasyuk, M. Solà and A. A. Voityuk. J. Phys. Chem. C 123 (2019) 16525-16532. Figure 1

Over the last years, carbon nano-onions (CNOs) have been in focus in material science research. Apart from its prospective use in solar cells, the number of potential applications of CNOs have grown in the last decades. Among them, we can mention their application in gas storage processes, solid lubrication, or heterogeneous catalysis, and also as electrode materials in capacitors, anode materials in lithium-ion batteries, catalyst support in fuel cells, or electro-optical devices. From the analysis of the polarizability of CNOs, it was concluded that CNOs behave as near perfect nanoscopic Faraday cages.[1] If CNOs behave as ideal Faraday cages, the reactivity of the C240 cage should be the same in Li+@C240 and Li+@C60@C240. In the first part of this work, we have analyzed the Diels-Alder reaction of cyclopentadiene to the free C240 cage and the C60@C240 CNO together with their Li+-doped counterparts using density functional theory. We find that in all cases the preferred cycloaddition is on bond [6,6] of type B of the C240 cage. From the comparison between the reactivity of Li+@C240 and Li+@C60@C240, we conclude that C60@C240 does not act as a perfect Faraday cage.[2] In the second part of this work, we perform a systematic study of excited state properties of six double-layered Li+ doped fullerenes of Ih symmetry: [Li@C60@C240]+, [Li@C60@C540]+, [Li@C60@C960]+, [Li@C240@C540]+, [Li@C240@C960]+ and [Li@C540@C960]+. On the basis of TDDFT calculations, we show that the long-wave absorption by the Li+ doped species leads to charge transfer (CT) between the inner and the outer shells unlike their neutral double-layered precursors. The CT energy depends strongly on the size of the concentric fullerenes and it can easily be tuned by varying both the encapsulated metal ion and the size of the shells. Two types of low-lying excited states are identified (1) capacitor-like structures, as Li+@C60 -@C240 +, with alternating positive and negative charges, and (2) states, where the positive charge is delocalized over the outer shell, as in Li@C240@C540 +.[3] References [1] R. R. Zope, J. Phys. B: At. Mol. Opt. Phys. 41 (2008) 41, 085101; [b] R. R. Zope, S. Bhusal, L. Basurto, T. Baruah and K. Jackson, J. Chem. Phys. 143 (2015) 084306. [2] A. J. Luque-Urrutia, A. Poater and M. Solà. Submitted for publication. [3] A. J. Stasyuk, O. A. Stasyuk, M. Solà and A. A. Voityuk. J. Phys. Chem. C 123 (2019) 16525-16532. Figure 1

Correction for ‘Cyclo[18]carbon: the smallest all-carbon electron acceptor’ by Anton J. Stasyuk et al., Chem. Commun., 2020, 56, 352–355.

We propose an atomic charge partitioning scheme, iterative adjusted charge partitioning (I-ACP), belonging to the stockholder family and based on partitioning of the valence molecular electron density. The method uses a Slater-type weighting factor c

Understanding photoinduced charge separation in fullerene-based dye-sensitized solar cells is crucial for the development of photovoltaic devices. We investigate here how the driving force of the charge separation process in conjugates of M@C80 (M=Sc3N, Sc3CH, Sc3NC, Sc4O2, and Sc4O3) with triphenylamine (TPA) depends on the nature of the metal cluster. Both singlet and triplet excited-state electron-transfer reactions are considered. These results based on TD-DFT calculations demonstrate that the driving force of charge separation in TPA-M@C80 can be tuned well by varying the structure of the metal cluster encapsulated inside the fullerene cage We are grateful for financial support from the Spanish Ministerio de Economía y Competitividad (MINECO) (Projects CTQ2014-54306-P and CTQ2015-69363-P), the Catalan DIUE (Project 2014SGR931, ICREA Academia 2014 Award to MS, and Xarxa de Referència en Química Teòrica i Computacional), and the FEDER fund (UNGI10-4E-801). J.P.M. acknowledges the Mexican National Council of Science and Technology (CONACYT) for his PhD fellowship (register/application number 217067/312543)

Photoinduced electron transfer in transition-metal complexes linked to a fullerene moiety is of increasing interest. Recently, several stereoisomers of an Ir-complex exhibiting configurational stability at metal center, which does not undergo epimerization have been synthesized (Angew. Chem. Int. Ed. 2017, 56, 2136). The presence of multiple electron donor and acceptor sites located at opposite ends with respect to the metallic center creates the prerequisites for the formation of entirely different charge transfer (CT) states. Here we report the results of quantum mechanical calculations and detailed analysis of excited-state properties for all stereoisomers of the junction. We found that the stereoisomers demonstrate clearly different CT properties by photoexcitation. The found photo-stereospecific effects can be used to design new hybrids with a different type of photoinduced CT state, exhibiting dissimilar activity in photocatalysis.

G-quadruplexes are four-stranded structures of nucleic acids that are formed from the association of guanine nucleobases into cyclical arrangements known as tetrads. G-quadruplexes are involved in a host of biological processes and are of interest in nanomaterial applications. However, not much is known about their electronic properties. In this paper, we analyze electronic excited states of G-quadruplexes using a combination of time-dependent DFT calculations and molecular dynamics simulations. We systematically consider experimentally observed arrangements of stacked guanine tetrads. The effects of structural features on exciton delocalization and photoinduced charge separation are explored using a quantitative analysis of the transition electron density. It is shown that collective coherent excitations shared between two guanine nucleobases dominate in the absorption spectrum of stacked G-tetrads. These excitations may also include a significant contribution of charge transfer states. Large variation in exciton localization is also observed between different structures with a general propensity toward localization between two bases. We reveal large differences in how charge separation occurs within different nucleobase arrangements, with some geometries favoring separation within a single tetrad and others favoring separation between tetrads. We also investigate the effects of the coordinating K+ ion located in the central cavity of G-quadruplexes on the relative excited state properties of such systems. Our results demonstrate how the nature of excited states in G-quadruplexes depends on the nucleobase stacking geometry resulting from the mutual arrangement of guanine tetrads his research was funded by Nanyang Technological grants (A.T.P. and M.-E.M.-B.) and by the grant CTQ2011-26573 from Ministry of Science and Innovation, Spain (A.A.V.)

The rate of photoinduced ET in molecular systems is controlled by electronic coupling of the locally excited and charge transfer states. We generalize the Bixon–Jortner–Verhoeven expression for electronic coupling to systems with a small energy gap and derive the transfer integral for charge separation in two model heterojunctions using the excitation energies and oscillator strengths computed with TD DFT. The estimated couplings are in good agreement with the reference values The authors acknowledge the support of the Ministerio de Economía y Competitividad of Spain (project CTQ2015-69363-P), Generalitat de Catalunya (project number 2014SGR931), and Xarxa de Referència en Química Teòrica i Computacional

A new computational scheme to calculate electronic coupling for photoinduced electron transfer and excitation energy transfer is described. The transfer integral between predefined quasi-diabatic states is expressed through adiabatic excitation energies of the system and expansion coefficients derived by decomposition of the transition density matrix of the reference states. To demonstrate the feasibility of the developed approach, electronic couplings for charge separation and exciton transfer in a heterojunction composed of quaterthiophene and C60 fullerene are computed at the DFT/ω-B97XD level.

he semiempirical method INDO/S is a well-known computational tool for calculating spectroscopic properties of molecular systems. This scheme has been modified and reparameterized using the TBE-2 benchmark excitation energies and oscillator strengths. The developed method referred to as INDO/X provides significant improvements over INDO/S. The mean absolute deviations of the INDO/X excitation energies relative to the TBE-2 data is 0.26 eV for singlet states and 0.33 eV for triplet states. The corresponding values for INDO/S are 0.56 and 0.64 eV. Also, the oscillator strengths estimated with INDO/X are in good agreement with the benchmark data. The proposed method is very fast and may be applied to large organic and biological molecules This work has been supported by grants CTQ2011-26573 from Ministry of Science and Innovation, Spain (MICINN)

Conversion of the sunlight into chemical energy is considered to be one of the most important and fundamental chemical reactions in nature. A broad variety of artificial photosynthetic systems based on dyads, triads and up to pentads involving electron donor and acceptor moieties have been designed and synthesized in order to investigate artificial photoinduced energy and electron transfer processes. In this work, we discuss a series of computational studies that involves the photoinduced charge separation in metal-cluster encapsulated triphenylamine-[80]fullerenes,[1] in a transition-metal complex linked to a fullerene moiety,[2] in an all-fullerene hetero-dumbbell formed by two fullerene units, namely C60 as the electron acceptor component and endohedral Lu3N@C80 as the donor unit,[3] and in four akamptisomers of quinoxalinoporphyrin–[60]fullerene complex.[4] References [1] J. P. Martínez, M. Solà and A. A. Voityuk. Chem. Eur. J. 22 (2016) 17305. [2] A. J. Stasyuk, O. A. Stasyuk, S. Filippone, N. Martín, M. Solà and A. A. Voityuk. Chem. Eur. J., 24 (2018) 13020. [3] Manuscript in preparation [4] A. J. Stasyuk, O. A. Stasyuk, M. Solà and A. A. Voityuk. Chem. Eur. J., 2019, ASAP, DOI: 10.1002/chem.201804999 Figure 1

G-quadruplex nucleic acids represent a unique avenue for the building of electrically conductive wires. These four-stranded structures are formed through the stacking of multiple planar guanine assemblies termed G-tetrads. The diverse folding patterns of G-quadruplexes allow for several geometries to be adopted by stacked guanine bases within the core and at the dimeric interface of these structures. It is currently not clear how different G-tetrad stacking arrangements affect electron hole mobility through a G-quadruplex wire. Using a combined quantum mechanics and molecular dynamics approach, we demonstrate that the electron-hole transfer rates within the G-tetrad stacks vary greatly for different stacking geometries. We identify a distinguished structure that allows for strong electronic coupling and thus enhanced molecular electric conductance. We also demonstrate the importance of sampling a large number of geometries when considering the bulk properties of such systems. Hole hopping within single G-tetrads is slower by at least two orders of magnitude than between stacked guanines; therefore, hole jumping within individual tetrads should not affect the hole mobility in G-quadruplexes. The results of this study suggest engineering G-tetrads with continuous 5/6-ring stacking from an assembly of single guanosine analogs or through modification of the backbone in G-rich DNA sequences.