In this work, a comprehensive view of the route that led to the construction of a theoretical approach to the functioning of DSSC is presented. The model was developed based on the theoretical interpretation of experimental results obtained along the years for solar cells including different dyes. This allowed the authors to generate the Barrera, Crivelli, Loeb (BCL) model. The method is based on a system of equations that uses time-dependent density functional theory (TDDFT) calculations to obtain a theoretical index, the Global Efficiency Index (GEI), for the efficiency of a sensitized solar cell. The GEI is obtained through the product of three factors: the available energy for injection, the amount of charge injected, and the efficiency of regeneration. The results so far obtained show a promising correlation with the experimental index of photo conversion efficiency (PCE). Moreover, the method provides theoretical tools that allow us to obtain an understanding of the operation of the cell, and provide us with the keys to optimize it. Its application to other type of devices, as, e.g., the highly more efficient perovskite solar cells, emerges as a challenging future goal.

In the search of novel coordination complexes with enhanced nonlinear optical activity, symmetrical bimetallic Rhenium complexes incorporating polypyridine plane bridging ligands are reported. The complexes studied were of the type (Re(CO)(3)Cl)(2)mu-N<<^>>N, with N<<^>>N 2,3-Dicarboxypyrazino[2,3-f][4,7]phenanthrolinedicarboxylic (L1), or 2,3-Diethoxycarbonylypyrazino[2,3-f] [4,7]phenanthroline (L2). Specifically, the physicochemical, solvatochromic, and nonlinear optical behaviour of the complexes were measured. DFT calculations were also performed, in order to improve the understanding of the observed phenomena. Spectroscopic characterization shows absorption bands at low energy associated to a charge transfer that involves the electronic transition from the Rhenium center and Chloride ligand towards the bridging ligand (Re(d) + Cl(n) -> L1(pi*); Re(d) + Cl(n) -> L2(pi*)) in both complexes. These bands are strongly dependent on the polarity of the solvent. This behaviour indicates a redistribution of the electronic density, mainly observed in the complex with L1. As expected, a relationship between solvatochromic effect and NLO response of the analyzed complexes was observed. The bimetallic complexes show a high NLO response, that is a noteworthy effect considering the symmetrical arrangement of the bimetallic complexes herein reported, the non-centro symmetry of these molecules being due to the carboxylic and ester groups only. (C) 2020 Elsevier Ltd. All rights reserved.

Density functional theory calculations of polypyridyl ruthenium complexes with polyaromatic ligands have been performed to understand the metal fragment effect on the modulation of their electronic properties and the influence on the aromatic character. The change of positions of the nitrogen atoms in the ligand structure, as well as the metal moiety, seems to influence the electronic behavior of the pi-extended structure and the aromatic character of the complexes at both the ground and excited states. In this framework, structural, electronic, and magnetic-based aromaticity indices were used to understand the aromaticity of the free and coordinated ligands. The aromaticity character of the ligands is highly influenced by the metal fragment, and the aromaticity/antiaromaticity is achieved according to both the electron-withdrawing capability of the ligand and the metal fragment. The electronic distribution observed on the aromatic ligand determines their pi-stacking ability; thus, it is proposed that the control of the pi-stacking ability is modulated according to the electronic nature of the ruthenium moiety.

Correction for ‘A comparative study of Ir(iii) complexes with pyrazino[2,3-f][1,10]phenanthroline and pyrazino[2,3-f][4,7]phenanthroline ligands in light-emitting electrochemical cells (LECs)’ by Iván González et al., Dalton Trans., 2015, 44, 14771–14781.

Lithium cations have been shown to impart an electrostatic Stark effect on molecules bound to mesoporous metal oxides commonly used in dye-sensitized solar cells. Herein, using the Barrera-Crivelli-Loeb theoretical model accompanied by Time Dependent Density Functional Theory calculations, we examined the influence that lithium cations have on the performance of dye-sensitized solar cells that incorporate [Ru(dmb)(2)(dcbH)](2+) sensitizers, where dmb is 4,4'-dimethyl-2,2'-bipyridine and dcbH is 4,4'-dicarboxylic acid-2,2'-bipyridine was examined. Simulations suggest that an enhanced photocurrent occurs in the presence of lithium cations, which is attributed to the photochemical generation of an excited-state dye lithium adduct. In this adduct, a lithium cation is interacting with the carbonyl moieties of the dcbH ligands, which results in a bathochromic shift of the [Ru(dmb)(2)(dcbH)](2+) metal-to-ligand charge-transfer spectral band. This shift in absorption can be canceled by introducing a hypothetical dipolar electric field of 7.3 MV/cm, in good agreement with experimentally reported values for Stark effects observed under solar excitation of TiO2 functionalized with these types of sensitizer molecules. This indicates that lithium cations not only interact with the metal-oxide semiconductor, as shown previously, but also interact directly with the dye upon photoexcitation, something that should be considered when designing and evaluating new sensitizers.

Influence of ancillary ligands derived from phenanthroline on the nature of the deactivation pathways of novel cationic Ir(iii) cyclometalated complexes.

The synthetic route to obtain the pyrazino polypyridinic type of ligands generally involves a condensation reaction between a diaminne and a dione. In the case of pyrazino[2,3-f][1,10]phenanthroline, ppl, and pyrazino[2,3-f][4,7]phenanthroline. ppz. a notoriously lower yield for the condensation reaction of the later has been observed. In this work, experimental results along with DFT methods allowed us to elucidate and improve the synthetic pathways involved in these ligands. Intermediary molecules for the corresponding condensation of dione and ethylenediamine were detected. By a continuous dialogue between theory and experiments the limiting reaction step was established as the formation of a "non -aromatic" intermediate, which was shown to be the cause for the lower yield observed for ppz. This intermediate was theoretically and experimentally characterized, thereby permitting us to facilitate its conversion to the desired product and obtain close to quantitative yield for the reaction.

In this work, the linear and nonlinear optical properties of a series of octupolar Zn(II) complexes with highly aromatic polypyridine ligands are investigated. The effect of the metal center on the spectroscopic properties of octupolar Zn (II) complexes are explored and compared to its respective free ligands. DFT and TD-DFT calculations were performed to gain more insights about the electronic and structural properties of these compounds. The aromaticity index of ligands and its modulation by Zn(II) in complexes was also theoretically studied. Quadratic hyperpolarizabilities (beta) were determined by using the Hyper-Light Scattering (HIS) technique at 1.06 mu m. Results show that beta values of the octupolar Zn(11) complexes are around three times higher than those of their respective ligands, which correlates with the number of ligands directly coordinated to the metal center. These results show how Zn(II) plays a positive structural role in the elaboration of highly transparent and active nonlinear optical molecules, without a significant electronic effect on the individual ligand NLO response, as expected when increasing the aromaticity of conjugated molecules.

The performance of ruthenium dye sensitized solar cells (DSSC) with different types of ligand was studied by means of a theoretical model where the ruthenium complex is bound to two [Ti(OH)3](+) units, instead of the more usual cluster TiO2 model. Electron injection is proposed to proceed from a thermalized (3)MLCT state rather than from higher vibrational excited states. The efficiency of the dye linked to the two [Ti(OH)3](+) units was determined in terms of a global index (ξ), calculated as the product of three theoretical indexes (FI) built from the results of time-dependent density functional theory (TDDFT) calculations. The index considers the harvested and delivered energy (F1), the charge transferred to the semiconductor (F2), and dye regeneration (F3). The results show that this set of parameters is unique for each dye, and allows the comparative evaluation of the performance of a series of dyes, with a different ancillary ligand at each stage of the cell operation. The method provides insights that can help explain the improved performance of N3 and black dyes compared to other dyes.

The synthesis and the electrochemical, photoluminescent and electroluminescent properties is reported for two new Ir(iii) cyclometalated complexes described as [Ir(F2ppy)2L1](PF6) and [Ir(F2ppy)2L2](PF6).

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

In this work three non-symmetric phenylpyridine type ligands, L1, L2 and L3, were designed, and their corresponding Iridium complexes, C1, C2 and C3, synthetized, in order to understand the effect of ligand asymmetry on the properties of the complexes, and to explore their potentiality in devices. The complexes were structurally characterized by NMR experiments and by X-ray Diffraction, and physicochemically by technics as UV/Vis and cyclic voltammetry. Theoretical DFT calculations of the energy and electronic density of the frontier orbitals of the complexes under study were also performed. The energy of the HOMO and LUMO correlated well with the experimental electrochemical data, and supported the understanding of the processes observed.

The kind invitation of Dr. Marinda Wu to give a talk at the "Women Leaders of the Global Chemistry Enterprise" Symposium" was the starting point for a long reflection about my nearly forty years devoted to academia, while facing the challenge of bringing up a family in a safe and nourishing environment. Ups and downs in both personal and academic life characterized this journey, which in essence was not really a trip in two parallel tracks, but two tangled routes that continuously crossed themselves, mixing and influencing each other. Looking back at the end of the road, I can see how everything fitted together and had a reason to occur. I am grateful to all that helped on this road. They pushed me up when everything seemed to slide down. The words of the Mexican poet Amado Nervo in his golden creation "In Peace" (Nervo, A.: "En Paz" in "Obras Completas, Tomo II Prosas-Poesias", Editorial Aguilar, Madrid, Spain, 1967, p.1733) best reflect my present feelings at this stage of my life:Close to my sunset I bless you, Life, Because you never gave me unfulfilled hope, Unfair work, or undeserved sorrow. ... ... .... Life, you owe me nothing. Life, we're at peace!

We report the comparative study of the electrochemical and photoluminescent properties of two Ir(iii) complexes described as [Ir(F2ppy)2(N^N)][PF6], where the F2ppy ligand is 2-(2,4-difluorophenyl)pyridine and the N^N ligands are pyrazino[2,3-f][1,10]phenanthroline (ppl) and pyrazino[2,3-f][4,7]phenanthroline (ppz). The complexes were used for the fabrication of light-emitting electrochemical cells (LECs). The structures of the complexes have been corroborated by X-ray crystallography. Theoretical calculations were performed to understand the photophysical behavior of the complexes. Both in solution and solid state, the photoluminescence spectra shows that emission is significantly red-shifted in the [Ir(F2ppy)2(ppz)][PF6] complex compared with the [Ir(F2ppy)2(ppl)][PF6] complex. Besides, the [Ir(F2ppy)2(ppl)][PF6] complex exhibits a higher quantum yield and a longer excited state lifetime than the [Ir(F2ppy)2(ppz)][PF6] complex; therefore, in the last case non-radiative decay is predominant due to the stabilization of LUMO orbital (energy gap law). In the fabrication of LEC devices with the [Ir(F2ppy)2(ppl)][PF6] complex, light emission was obtained with a maximum value of luminance equal to 177 cd m(-2), while in the case of the [Ir(F2ppy)2(ppz)][PF6] complex, no luminance was observed. According to the photophysical data, the performance in LEC devices could be explained by the different position of the nitrogens in the ppl and ppz structural isomers, electronically affecting the complex, and therefore its properties. In addition, from the crystallographic analysis it is possible to note that the [Ir(F2ppy)2(ppz)][PF6] complex shows enhanced intermolecular and intramolecular interactions compared with [Ir(F2ppy)2(ppl)][PF6], and consequently a higher ordering of the molecules in the complex with ppz ligand can be expected. This higher order could favour the quenching processes, and consequently enhance the non-radiative deactivation.

We synthesized a new family of Ir-III complexes [Ir(R-1-ppy)(2)(R-2-ppl)](PF6), where R-1-ppy = 2-phenylpyridine (ppy) or 2,4-difluorophenylpyridine (F-2-ppy) and R-2-ppl = pyrazino[2,3-f][1,10]phenanthroline (ppl) or 2,3-diethoxycarbonylpyrazino [2,3-f][1,10]phenanthroline (deeppl). The complexes were experimentally and theoretically characterized, noting the importance of the R-1 substituent on the modulation of HOMO level and its impact on the electronic properties. These compounds exhibit high second-order nonlinear optics (NLO) activity, especially, those with F-2-ppy ligands; this substituent modulates the charge transfer, optimizing the NLO response. The compounds also show blueshifted emissions, both in solution and as a solid film, which is desirable for use in light-emitting devices. This is the first use of the synthesized complexes for application in the two tasks.

In this work we report the preparation of six new donor-metal-acceptor (D-M-A) type complexes of ruthenium(II) with the highly absorbing "chromophoric" ligand 4,4'-bis(2-(4-methoxyphenyl)styryl)-2,2'-bipyridine, (L-OCH3, donor moiety) and substituted polypyridinic ligands with electron acceptor character (NN-A). The NN-A studied ligands were pyrazino[2,3-f][1,10]phenanthroline (ppl), 11-R-dipyrido[2,3-a:2',3'-c]phenazine (dppz-R; R is H, NO2, or CN) and 10,11-[1,4-naphtalenedione]dipyrido[3,2-a:2',3'-c]phenazine (Aqphen). The complexes were characterized by IR, NMR, UV-Vis spectroscopy and cyclic voltammetry. The potential NLO response of the complexes was evaluated by solvatochromic studies. Although the communication between D and A exists, the effect of the change of the acceptor moiety on the properties of the complexes is small and the behavior of the complexes is governed mainly by the donor ligand. The Metal to Ligand Charge Transfer bands (MLCT) exhibited by all complexes in the visible region have dominant electronic density transfer character from the metal to the chromophoric L-OCH3 ligand. The hypsochromic shift of this low energy absorption band on going from a less polar (benzene) to a more polar solvent (acetonitrile) indicated that a redistribution of the electronic density among the metal and the donor ligand is observed. This behavior permits to predict a NLO response for these types of complexes. The combination of high molar absorptivity with intraligand charge transfer (ILCT) mixing into the MLCT bands are encouraging for the generation of new materials with interesting NLO properties. (C) 2014 Elsevier Ltd. All rights reserved.

The cationic Ir(III) complex with 7,8-benzoquinoline (bzq) as cyclometalating ligand and 4,4'-diterbutyl-2,2'-bipyridine (tBuB) as ancillary ligand, [Ir(bzq)(2)(tBuB)](PF6) (1), was utilized in the fabrication of a light-emitting electrochemical cell (LEC). The photophysical properties and the characterization of the LEC device with this complex was compared with literature data for the analogous complex with 2-phenylpyridine (ppy), [Ir(ppy)(2)(tBuB)](PF6) (2). Complex 1 showed blue shifted emission compared to complex 2. Surprisingly, complex 1 shows lower luminance, efficiency and stability in regard to 2. This behavior correlated well with the low values of quantum yield and lifetime, registered for complex 1 in solution. The performance observed is unexpected, taking into account the emission wavelengths recorded for each complex, and the lesser non radiative deactivation processes expected for a complex with a more rigid ligand as bzq. A possible explanation of this behavior is given in terms of the predominance of a fluorescent emission in the case of the complex 1 instead of a phosphorescent emission, as observed for complex 2.

The photophysical properties of polypyridinic Ruthenium complexes, as potential semiconductor materials for iTMC (ionic transition metal complex) type LECs have been studied. Substituted 2,2'-bipyridine ligands were used to study the effects of conjugated and aliphatic chains on the properties of the complexes, especially on the photophysical properties. Specifically, the N<^>N type ligands 4,4'-bis[2-hydroxy-2-(phenyl)ethyl]-2,2'-bipyridine (1), 4,4'-bis(alpha-styrene)-2,2'-bipyridine (2) and 4,4'-diphenylethyl-2,2'-bipyridine (3) were synthesized, and used to prepare the corresponding [Ru-II(bpy)(2)(N boolean AND N)](PF6)(2) complexes. All three ligands contain a phenyl group as substituent for bpy, but with different residues as bridges between both: ligands 1 and 3 have free rotating connecting groups, while 2 is more rigid due to the styryl double bond. From the achieved results it was observed that, as expected, a conjugation on the ligand produces complexes with bands shifting toward lower energy regions, due to the electronic communication between the phenyl and bipyridine groups. On the contrary, in the absence of this conjugation, as is the case of the complexes with ligands 1 and 3, absorptions and emissions bands are very similar to the corresponding complex with unsubstituted bpy. Therefore, complexes with ligands 1 and 3 seem to be promising for LEC devices, due to the free rotations of the connecting aliphatic chain. This should preserve the properties as emission color, and advantages of Ru(bpy)(3)(2+) photoluminescence, but increasing the efficiency when used in a device, avoiding crystallization and diminishing self-quenching processes. (C) 2014 Elsevier B.V. All rights reserved.

The ligands of type pyrazino[2,3-f][1,10]phenanthroline, R2ppl, with R = CN, COOH, COOEt or OH, were synthesized and used as precursors for obtaining the corresponding series of complexes of type [Ru(dmbpy)2R2ppl](PF6)2, where dmbpy is 4,4′-dimethyl-2,2′-bipyridine. The compounds were prepared, characterized, and studied by theoretical DFT calculations in order to evaluate their potentiality as dyes in photoelectrochemical cells. The electron acceptor capacity of the R2ppl ligands was evaluated by analyzing parameters such as electrophilicity and charge distribution on the reduced ligand. Additionally, the R substituents on R2ppl were evaluated as anchoring groups, by variables such as highest spin occupied molecular orbital (HSOMO). Finally, the IT parameter was defined and calculated. This is related to the amount of energy that can be delivered to TiO2 from the acceptor anchoring ligand in the thexi state. According to this parameter, the [Ru(dmbpy)2(COOH)2ppl](PF6)2 complex is predicted to have the best response, among the compounds of the series, when used as dye in a solar cell.