A theoretical survey of the UV–visible spectra of axially and peripherally substituted boron subphthalocyanines

The UV–visible spectra of a series of subphthalocyanines (SubPcs) characterized by three different axial substituents (An ) in combination with H, F, NO2, SO2 H and SO2 CH3 peripheral substituents (Ri ) were predicted and analyzed by means of time-dependent DFT calculations, including chloroform as a solvent. In this analysis, we paid particular attention to the Q band, which remained almost unchanged regardless of the nature of the axial substituent. For the same axial substituent, changes in the Q band were also rather small when hydrogens at the periphery were replaced by R1 = SO2 H and R1 = R2 = SO2 H. However, the shifting of the Q band was almost 10 times larger when R1 = NO2 and R1 = R2 = NO2 due to the participation of this substituent in the π SubPc cloud. In most cases, the characteristics of the spectra can be explained considering only the transitions involving the HOMO-1, HOMO, LUMO and LUMO + 1 orbitals, where the Q band can be decomposed into two main contributions, leading to charge separation. Only for SubPc(A3,F,F,H) would one of the two contributions from the deepest orbital involved not lead to charge transfer. For this latter case, the HOMO-2 orbital must also be taken into account. In summary, the results obtained with the analysis of the MO indicate that the studied SubPcs are appropriate for photochemical device

Alkaline-earth (Be, Mg and Ca) bonds at the origin of huge acidity enhancements

The interaction between alkaline-earth derivatives with the general formula X2M (X = H, F and Cl; M = Be, Mg and Ca) and a set of Lewis bases, including first and second-row hydrides, namely YHn(Y = O, N, F, S, P and Cl) hydrides, as well as other typical cyclic organic bases, such as aniline, 1H-1,2,3-triazole, 1H-tetrazole and phenylphosphine, was investigated using the G4 ab initio composite method. Contrary to what was expected, it was found that the interactions involving Mg and Ca derivatives were not necessarily weaker than those between beryllium bonds. The origin is two-fold: larger deformation of the interacting systems when Be-derivatives are involved and appearance of secondary non-covalent interactions in the formation of some of the Mg- and Ca-containing complexes. Hence, the dissociation of the latter complexes may require higher enthalpies than that of the Be complexes. These deformations are triggered by a significant redistribution of electron density of the two interacting moieties, which also result in dramatic changes in the reactivity of the interacting compounds and in particular in the intrinsic basicity of the Lewis bases investigated, to the point that conventional bases, such as ammonia or aniline, upon complexation with MCl2(M = Be, Mg and Ca), become stronger Brønsted acids than phosphoric acid, whereas other bases, such as 1H-tetrazole, become stronger acids than perchloric acid.This work was carried out with financial support from the Ministerio de Economía, Industria y Competitividad (projects CTQ2015-63997-C2 and CTQ2013-43698-P), by the COST Action CM1204 and Comunidad Autónoma de Madrid (S2013/MIT2841, Fotocarbon

Intramolecular magnesium bonds in malonaldehyde-like systems. A critical view of the resonance-assisted phenomena

Through the use of high-level G4-theory calculations we have investigated the structure, stability and bonding of a set of Mg derivatives formed by replacing the –OH group of malonaldehyde or only the hydrogen atom of this group by a –MgH group. To give insight on the resonance-assisted phenomenon, which might be involved in the stabilization of these compounds, we also included the corresponding saturated analogues in our survey. The effect of the rigidity of the molecular framework was considered by analyzing the Mg-derivatives of (Z)-4-(hydroxymethylene)cyclobut-2- enone, obtained through the same substitutions mentioned above. The effect of replacing the carbonyl group by an imino group was also contemplated. In all cases, the global minimum is a cyclic conformer stabilized through the formation of rather strong intramolecular magnesium bonds. The strength of these interactions is directly related with the intrinsic basicity of the carbonyl group (or the imino group) and the intrinsic acidity of the –MgH group, rather than with a resonance-assisted phenomenon. As a matter of fact, for all the investigated systems, the conclusion is that resonance in the cyclic conformer is directly correlated with the strength of the intramolecular magnesium bond, and not vice-versa. Interestingly, the strength and characteristics of these interactions for these Mg-containing derivatives are very similar to those of the corresponding Be-containing analoguesWork supported by the Projects CTQ2015-63997-C2 and CTQ2016-76061-P of the Ministerio de Economía y Competitividad of Spain, FOTOCARBON-CM S2013/MIT-2841 of the Comunidad Autónoma de Madrid and by the COST Action CM1204 of the EU Framework Programme. Horizon 202

Strong interactions between copper halides and unsaturated systems: New metallocycles? or the importance of deformation

The complexes formed by CuF with CC double and triple bonds have been studied at the MP2 and CCSD(T) computational levels. The interaction of CuF with acetylene, ethylene and their fluoro derivatives is very strong, with interaction energies close to those of conventional covalent bonds. Hence, these complexes could be actually viewed as a new kind of metallocycles, with significantly strong Cu-C linkages. All electronic indexes analyzed by means of the AIM, ELF and NBO formalisms, indicate that the strength of the interaction should increase with the number of fluorine substituents in both series of compounds. Surprisingly, however, although both series of compounds exhibit the same bonding arrangements, they follow opposite stability trends and the expected increase of the interaction energies with the number of fluorine substituents is only observed in the acetylene series. The reason for this unexpected behavior is once more associated with the effects triggered by the distortion of the interacting subunits. Deformation not only has a direct energetic cost but dramatically affects the intrinsic properties of the interacting systems. © 2012 the Owner Societies.Peer Reviewe

Strong interactions between copper halides and unsaturated systems: New metallocycles? or the importance of deformation

The complexes formed by CuF with CC double and triple bonds have been studied at the MP2 and CCSD(T) computational levels. The interaction of CuF with acetylene, ethylene and their fluoro derivatives is very strong, with interaction energies close to those of conventional covalent bonds. Hence, these complexes could be actually viewed as a new kind of metallocycles, with significantly strong Cu-C linkages. All electronic indexes analyzed by means of the AIM, ELF and NBO formalisms, indicate that the strength of the interaction should increase with the number of fluorine substituents in both series of compounds. Surprisingly, however, although both series of compounds exhibit the same bonding arrangements, they follow opposite stability trends and the expected increase of the interaction energies with the number of fluorine substituents is only observed in the acetylene series. The reason for this unexpected behavior is once more associated with the effects triggered by the distortion of the interacting subunits. Deformation not only has a direct energetic cost but dramatically affects the intrinsic properties of the interacting systems. © 2012 the Owner Societies.Peer Reviewe

Dynamic interaction of VCAM-1 and ICAM-1 with moesin and ezrin in a novel endothelial docking structure for adherent leukocytes

Ezrin, radixin, and moesin (ERM) regulate cortical morphogenesis and cell adhesion by connecting membrane adhesion receptors to the actin-based cytoskeleton. We have studied the interaction of moesin and ezrin with the vascular cell adhesion molecule (VCAM)-1 during leukocyte adhesion and transendothelial migration (TEM). VCAM-1 interacted directly with moesin and ezrin in vitro, and all of these molecules colocalized at the apical surface of endothelium. Dynamic assessment of this interaction in living cells showed that both VCAM-1 and moesin were involved in lymphoblast adhesion and spreading on the endothelium, whereas only moesin participated in TEM, following the same distribution pattern as ICAM-1. During leukocyte adhesion in static or under flow conditions, VCAM-1, ICAM-1, and activated moesin and ezrin clustered in an endothelial actin-rich docking structure that anchored and partially embraced the leukocyte containing other cytoskeletal components such as α-actinin, vinculin, and VASP. Phosphoinositides and the Rho/p160 ROCK pathway, which participate in the activation of ERM proteins, were involved in the generation and maintenance of the anchoring structure. These results provide the first characterization of an endothelial docking structure that plays a key role in the firm adhesion of leukocytes to the endothelium during inflammation

Cellular integrin ¿5ß1 and exosomal adam17 mediate the binding and uptake of exosomes produced by colorectal carcinoma cells

Approximately 25% of colorectal cancer (CRC) patients develop peritoneal metastasis, a condition associated with a bleak prognosis. The CRC peritoneal dissemination cascade involves the shedding of cancer cells from the primary tumor, their transport through the peritoneal cavity, their adhesion to the peritoneal mesothelial cells (PMCs) that line all peritoneal organs, and invasion of cancer cells through this mesothelial cell barrier and underlying stroma to establish new metastatic foci. Exosomes produced by cancer cells have been shown to influence many processes related to cancer progression and metastasis. In epithelial ovarian cancer these extracellular vesicles (EVs) have been shown to favor different steps of the peritoneal dissemination cascade by changing the functional phenotype of cancer cells and PMCs. Little is currently known, however, about the roles played by exosomes in the pathogenesis and peritoneal metastasis cascade of CRC and especially about the molecules that mediate their interaction and uptake by target PMCs and tumor cells. We isolated exosomes by sizeexclusion chromatography from CRC cells and performed cell-adhesion assays to immobilized exosomes in the presence of blocking antibodies against surface proteins and measured the uptake of fluorescently-labelled exosomes. We report here that the interaction between integrin 5 1 on CRC cells (and PMCs) and its ligand ADAM17 on exosomes mediated the binding and uptake of CRC-derived exosomes. Furthermore, this process was negatively regulated by the expression of tetraspanin CD9 on exosome

Tetraspanin-decorated extracellular vesicle-mimetics as a novel adaptable reference material

Features like small size, low refractive index and polydispersity pose challenges to the currently available detection methods for Extracellular Vesicles (EVs). In addition, the lack of appropriate standards to set up the experimental conditions makes it difficult to compare analyses obtained by different technical approaches. By modifying synthetic nanovesicles with recombinant antigenic regions of EV-enriched tetraspanins, we aimed to construct an EV-mimetic that can be used as a suitable standard for EV analyses. To this end, the sequences of the large extracellular loops of the tetraspanins CD9, CD63 and CD81 were tagged with a target sequence for the biotin ligase BirA, and co-transformed with a BirA expression plasmid into Escherichia coli. GST fusion proteins were then isolated by affinity chromatography and released using thrombin. Biotinylated recombinant tetraspanin-loops were then coupled to (strept)avidin-coated synthetic nanovesicles and analysed and characterised by Dot-blot, Western-blot, Nanoparticle Tracking Analysis, Flow Cytometry and Transmission Electron Microscopy. With this method, we were able to efficiently produce tetraspanin-domain decorated nanovesicles that share biophysical properties with natural EVs, can be detected using specific antibodies against common EV markers such as tetraspanins, and can be used as robust reference materials for detection techniques that are often used in the EV field.This research was supported by grants from Fundación Ramón Areces and Ministerio de Economía y Competitividad (BFU2014-55478-R, REDIEX. SAF2015-71231-REDT, BIO201786500-R) cofounded by FEDER funds. E.L-A. was supported by the European Social Fund, GEIVEX Mobility and Universidad Autónoma de Madrid STS fellow ships,as well as by the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No.72214

Experimental thermochemical study of two 2-alkylbenzimidazole isomers (alkyl = propyl and isopropyl)

This paper reports the values of the standard (p∘=0.1 MPa) molar enthalpy of formation in the condensed, at T=298.15 K, for 2-R-benzimidazoles (R=propyl, isopropyl), derived from, the respective enthalpies of combustion in oxygen, measured by static bomb combustion calorimetry and the standard molar enthalpies of sublimation, at T=298.15 K, obtained using Calvet microcalorimetry in the case of 2-isopropylbenzimidazole and, by the variation of vapour pressures, determined by the Knudsen effusion technique, with temperatures between (344 and 365) K for 2-propylbenzimidazole. Heat capacities, in the temperature ranges from T=268 K to near their respective melting temperatures, T=421 K for 2-propylbenzimidazole and T=464 K for 2-isopropylbenzimidazole, were measured with a differential scanning calorimeter. These values were used to derive the standard molar enthalpies of formation, of the two 2-benzimidazole derivatives, in gaseous phase.Thanks are due to Instituto de Cooperação Cientı́fica e Tecnológica Industrial (ICCTI), Lisbon, Portugal, and Consejo Superior de Investigaciones Cientı́ficas (CSIC), Madrid, Spain for a joint research project CSIC/ICCTI; M.L.P.F.A. thanks Fundação para a Ciência e Tecnologia (FCT), Lisbon, Portugal, for the award of a postdoctoral fellowship (SRFH/BPD/5595/2001). The Spanish DGI/MCyT is acknowledged under projects BQU2000-0252, 0906 and 1497; M.T. thanks MECD/SEEU, AP2002-0603, Spain for financial support

Substituent effects on enthalpies of formation of nitrogen heterocycles: 2-substituted benzimidazoles and related compounds

The enthalpies of combustion, heat capacities, enthalpies of sublimation and enthalpies of formation of 2-tert-butylbenzimidazole (2tBuBIM) and 2-phenylimidazole (2PhIM) are reported and the results compared with those of benzene derivatives and a series of azoles (imidazoles, pyrazoles, benzimidazoles and indazoles). Theoretical estimates of the enthalpies of formation were obtained through the use of atom equivalent schemes. The necessary energies were obtained in single-point calculations at the B3LYP/6-311++G(d,p) on B3LYP/6-31G* optimized geometries. The comparison of experimental and calculated values of all studied compounds bearing H (unsubstituted), methyl (Me) ethyl (Et), propyl (Pr), isopropyl (iPr), tert-butyl (tBu), benzyl (Bn) and phenyl (Ph) groups show remarkable homogeneity. The remarkable consistency of both the calculated and experimental results allows us to predict with reasonable certainty the missing experimental values. The crystal and molecular structure of the 2-benzylbenzimidazole (2BnBIM) has been determined by X-ray analysis. The observed molecular conformation permits the crystal being built up through N−H···N hydrogen bonds and van der Waals contacts between the molecules. An attempt has been made to relate the crystal structure to the enthalpies of sublimation.Thanks are due to Instituto de Cooperac¸a˜o Cientı´fica e Tecnolo´gica International (ICCTI), Lisbon, Portugal, and Consejo Superior de Investigaciones Cientı´ficas (CSIC), Madrid, Spain. L.M.P.F.A. thanks Fundac¸a˜o para a Cieˆncia e Tecnologia (FCT), Lisbon, Portugal, for the award of a postdoctoral fellowship (PRAXIS XXI/BPD/16319/98). This work has also been financed by DGICYT (BQU-2003- 00894, -00976 and -01251)