Benzimidazoles are a group of heterocyclic compounds which have been applied in numerous aspects of science and technology. As a result of their interesting electronic and optical properties when incorporated in push-pull systems, benzimidazole derivatives found application as solvatochromic and fluorescent probes, chemosensors, organic light emitting diodes (OLEDs) and non-linear optical (NLO) chromophores.^[1]

In the last decade our research group has reported experimental and theoretical results regarding the auxiliary donor/acceptor effect of electron deficient benz-X-azole derivatives in push-pull systems.^{[1b-c, 1e, 1g-i]} In this work we describe the synthesis, UV-visible absorption, fluorescence and solvatochromic studies of a series of heterocyclic chromophores of the benzimidazole type. These new bithienyl-benzimidazoles were synthesised in good to excellent yields, by metal-free one-step reaction of o-nitroanilines in the presence of formyl-bithiophenes, via a reductive cyclization, and their optical and solvatochromic properties were evaluated in solvents of different character.

References:

1. (a) Esteves, C. I. C.; Batista, R. M. F.; Raposo, M. M. M.; Costa, S. P. G. Dyes Pigments 2016, 135, 134-142; (b) Baptista, R. M. F.; Isakov, D.; Raposo, M. M. M.; Belsley, M.; Bdikin, I.; Kholkin, A. L.; Costa, S. P. G.; Gomes, E. D. J. Nanopart. Res. 2014, 16 (7); (c) Garcia-Amorós, J.; Reig, M.; Castro, M. C. R.; Cuadrado, A.; Raposo, M. M. M.; Velasco, D. Chem. Commun. 2014, 50 (51), 6704-6706; (d) Pina, J.; Seixas de Melo, J. S.; Batista, R. M. F.; Costa, S. P. G.; Raposo, M. M. M. J. Org. Chem. 2013, 78 (22), 11389-11395; (e) Garcia-Amorós, J.; Castro, M. C. R.; Coelho, P.; Raposo, M. M. M.; Velasco, D. Chem. Commun. 2013, 49 (97), 11427-11429; (f) Batista, R. M. F.; Ferreira, R. C. M.; Raposo, M. M. M.; Costa, S. P. G. Tetrahedron 2012, 68 (36), 7322-7330; (g) Coelho, P. J.; Castro, M. C. R.; Fonseca, A. M. C.; Raposo, M. M. M. Dyes Pigments 2012, 92 (1), 745-748; (h) Raposo, M. M. M.; Castro, M. C. R.; Belsley, M.; Fonseca, A. M. C. Dyes Pigments 2011, 91 (3), 454-465; (i) Batista, R. M. F.; Costa, S. P. G.; Belsley, M.; Raposo, M. M. M. Tetrahedron 2007, 63 (39), 9842-9849.

Acknowledgements

Thanks are due to Fundação para a Ciência e Tecnologia (Portugal) for financial support through project FEDER-COMPETE for financial support through the CQ/UM PEst-C/QUI/UI0686/2013 (FCOMP-01-0124-FEDER-037302) and a post-doctoral grant to R.M.F. Batista (SFRH/BPD/79333/2011). The NMR spectrometer Bruker Avance III 400 is part of the National NMR Network, and was purchased with funds from POCI2010 (FEDER) and FCT.

A computational study is carried out regarding the characteristics of a set of fullerene complexes formed by the fullerene C₇₈ and the endohedral fullerene Sc₃N@C₇₈ with a series of hosts of different nature, including corannulene, a zinc porphyrin and a chloro boron subphthalocyanine. The carbon cage is kept similar in these two fullerenes, so comparing the results obtained for their complexes will reveal the role of the endohedral cluster on modifying the characteristics of the fullerene and how it affects to the interaction.

Abstract – The aim of this work is the design, synthesis and characterization of a series of phenylboronic cyclometallated derivatives bearing different phosphines. Palladium cyclometallated compounds have proved to be useful as catalysts in cross coupling reactions [1, 2]. In particular, palladacycles with a boronic acid function may lead to further modifications applicable to the Suzuki-Miyaura reaction [3], thus modifying the properties of the compounds. Reactivity towards phosphine ligands provides different structures [4] that modulate the applicability to the coupling reaction.

The compounds were prepared by reaction of cyclometallated species with different phosphine ligands and they were characterized by IR, ¹H and ³¹P NMR spectroscopy.

Acknowledgements - We wish to thank the financial support received from the Xunta de Galicia (Galicia, Spain) under the Grupos de Referencia Competitiva Programme Projects GRC2015/009. F. Reigosa and F. Lucio thank the Spanish Ministry of Education (grant FPU15/07145 and FPU13/05014).

References

[1] M. Ohff; A. Ohff; M.E. van der Boom; D. Milstein; J. Am. Chem. Soc., 1997, 119, 11687.

[2] R.N. Prabhu; R. Ramesh; Tetrahedron Letters, 2013, 54, 1120.

[3] Adrio, L.A., PhD Dissertation, University of Santiago de Compostela, 2006.

[4] Bermúdez, B., PhD Dissertation, University of Santiago de Compostela, 2014.

Transition metal complexes are useful in organic synthesis due to the capability of the metal to activate substrates [1-2]; in particular, cyclometallation reactions may lead to novel routes in organic synthesis. Thiosemicarbazones show a high coordinative capacity given that they possess several potential donor atoms through which they can bind to transition metals. In addition, thiosemicarbazones as well as their semicarbazones analogues have considerable biological and pharmacological interest [3] because of their antibacterial, antiviral and antitumor activity. Their derivatives with ferrocenyl phosphines such as 1,1′‑bis(diphenylphosphino)ferroceno (dppf) show a wide range of applications [4].

This communication includes the preparation and characterization of a series of thiosemicarcarbazones and of their organometallic complexes with palladium and iron.

Acknowledgments

We wish to thank the financial support received from the Xunta de Galicia (Galicia, Spain) under the Grupos de Referencia Competitiva Programme Projects GRC2015/009.

References:

[1]- R. N. Prabhu; R. Ramesh, Tetrahedron Lett., 2013, 54, 1120.

[2]- R. N. Prabhu; R. Ramesh, Tetrahedron Lett., 2012, 53, 5961.

[3] S. Cruz; S. Bernés; P. Sharma; R. Vazquez; G. Hernandez; R. Potillo; R. Gutierrez, Appl. Organomet. Chem., 2010, 24, 8.

[4]- A. Togni; T. Hayashi, Ferrocenes, 1995.

In the last few years, chemists have tried to adapt chemical reactions in order to comply with the principles of green chemistry. Consequently, our challenge is to use specific behaviors observed in ionic liquids (ILs) and transform them into a benefit on a reactive process. Is known that dual action as catalyst and solvent, conduces to more mild reaction conditions.

We have reported this behaviour of protic ionic liquids (PILs) as Ethyl Ammonium Nitrate (EAN).  Taking into account this, our goal is to use these conducts of PILs to develop alternative methods of interest in organic synthesis. In this sense, the allilyc amines are molecules that acquirer interest as building blocks in the path of synthesis of products with biological activity such as herbicides, antibiotics and insecticides. The methods for obtaining allylic amines are scarce and with a high number of stages. As a consequence, we have the purpose of making reactive systems of dienes and PIL base alkyl ammonium that facilitate the obtaining of such precursors through green synthetic strategies. Advantages of these strategies are that they are economic in stages and develop in more benign reaction conditions.

It is known from the specialty literature that many biological processes, like: bone and vascular remodeling, carcinogenesis, renal function, cardiac hypertrophy, gastrointestinal homeostasis, and reproductive function, are closely related to EP4 signaling. This protein is one of the four receptor subtypes identified for prostaglandin E2 (PGE2), namely: EP1, EP2, EP3 and EP4, which belong to the larger class of G-protein-coupled receptors. In this work, a previously reported homology model of EP4 was used for docking studies of potent EP4 ligands, in order to provide information about protein - ligand interaction patterns. Glide software, from the Schrödinger package, with XP extra precision option, was used for docking simulations. Among the amino acids residues from the EP4 binding site that made interactions with the ligands taken in our study, the key residue Ser285 (highlighted, also, in mutagenesis studies) was noted. The observed interactions between ligands and amino acid residues consist in several hydrogen bonds (e.g. with Thr175, His181, Ser95, Ser103, Asp311) and hydrophobic interactions (e.g. with Ala314, Tyr186). The outcome resulted from the docking studies led to a better understanding of how the agonists and antagonists bind in situ and may lead to the discovery of selective and new active compounds.

Benzofuran (oxygen heterocycle) is a common moiety found in many biologically active natural and therapeutic products, and thus represents a very important pharmacophore. It is present in many medicinally important compounds that show biological activity, including anticancer and antiviral properties. Some benzofuran derivatives are also known as 5-lipoxygenase inhibitors, antagonists of the angiotensin II receptor, blood coagulation factor Xa inhibitors, ligands of adenosine A1 receptor and more recently as MAO inhibitors. In general, benzofurans described as MAO inhibitors have a higher selectivity to the MAO-B isoform. In our efforts to contribute to the development of novel compounds that may be useful in the treatment of neurodegenerative disorders such as PD or AD, we are focusing on 2-phenylbenzofuran derivatives. 2-Phenylbenzofurans have been selected by analogy to 3-phenylcoumarins previously described by us as potent and selective MAO-B inhibitors, and preserving the core of trans-stilbene in their structure. Based on these previous experimental results, and with the aim of finding novel and more selective MAO-B inhibitors, in the present work we continue our studies, describing the synthesis of a new series of nitro-substituted 2-phenylbenzofurans derivatives in order to compare experimental results.

Ionic liquids (ILs) present unique physicochemical properties such as negligible vapour pressure and high solubility in different solvents; therefore, they have been used in several areas of chemistry with success.¹

Some ILs show amphiphilic character² presenting better  surface-active properties than conventional surfactants.³ Because of this, ILs have emerged as a superior class of surfactants.⁴

In this communication, the design and synthesis of new task-specific amino acid based ILs to be used as surfactants is reported; for this purpose, long alkyl chains were introduced into their structures. The selected ILs were designed aiming low toxicity and viscosity and high biodegradability as well as high thermal stability. Due to the low toxicity of amino acids, cations derived from proline were selected; ⁵ in addition, these cations allow simple variations on the side chain and nitrogen quaternization. Taking into account the known application of dodecylsulfate and dodecylbenzenesufonates surfactants, they were selected as anions.

The general procedure used to  synthesize these ILs involves two steps: esterification and quaternization of the amino acid using different alcohols and later anion exchange.

Reference:

[1] Plechkova, N.V.; Seddon, K.R., Chem. Soc. Rev., 2008, 37, 123-150.

[2] Singh, G.; Singh, G.; Zhang, S.; Kang, T.S., J. Phys. Chem. B, 2016, 120, 1092-1105.

[3] Cognigni, A.; Gaertner, P.; Zirbs, R.; Peterlik, H.; Prochazka, K.; Schroder, C., Bica, K., Phys. Chem. Chem. Phys, 2016, 18, 13375-13384.

[4] Huang, B.; Huang, C.; Jinging, C.; Xiaoqui , S., J. Alloys Compd., 2017, 712, 164-171.

[5] Trivedi, T. J.; Srinivaa Rao, K.;  Singh, T.; Kumar Mandal, S.; Sutradhar, N.; Panda, A.B.; Kumar, A., ChemSusChem, 2011, 4, 604-608.

We present a systematic theoretical study about In_n clusters with n=1-10. We explore the lowest-energy structures and investigate their geometric and electronic properties including electronic affinity (EA), ionization potential (IP), HOMO-LUMO gap, second difference of cluster total energy (∆₂E) and spin density (SD) using the DFT method with the B3LYP and M06 functionals, and LANL2DZ.

As a measure of the complexs relative stability, we calculate the binding  energy per atom (E_b) and we observe that increases together with the size of the cluster (up to n=7) and then remains constant at 1,27 eV/atom. Besides, the same lowest-energy structures are obtained with B3LYP and M06, except for In₃ and In₅.

The analysis of EA and IP is reliable with previous DFT results for other metals and calculations using B3LYP present better results according to the bibliography. The HOMO-LUMO gap exhibit odd-even oscillations. For both functionals are observed similar behaviors up to n=6, but do not correlate with the electron-pairing effect according to previous works. For n>6, with M06, maximums in even-clusters are obtained, indicating a more consistent result. Regardless the functional chosen, the ∆₂E it’s higher for In₃ and In₈, indicating that this clusters are most stables than their neighbors. Finally the SD is strongly dependent on the shape and size of the cluster: small changes in the structure cause large changes in the SD and when the number of atoms increases, the reactivity decreases because the spin is scattered over a larger surface.

Growing demands of miniaturization and high performance in a wide variety of applications, from biomedicine to electronics, have generated new solutions concerning the obtaining of multifunctional materials. In this context, a way to compensate the weaknesses of a conductive polymer assumes its use together with another polymer. Such of blend was prepared by embedding of cellulose acetate phthalate in the quaternized polysulfone matrix. By analyzing the transmission spectra of pure polymer films and their blends was obtained the transparency, an important parameter for optical performances. At the same time, the dependence of dielectric properties and conductivity on frequency of these blends was studied. The dielectric constants have low values for the studied blends, being dependent on the chemical characteristics of blends compounds, in relation with the charge transfer complex and free volume and, consequently, with packing of the polymer chains and of the polarizable groups per volume units. Two relaxation processes occuring in polymers blend, caused by low-amplitude non-cooperative motion of kinetic units in side groups and a low-temperature caused by the large-scale cooperative motion of kinetic units in the main polymer chain, have been revealed. Moreover, the electrical conductivity of studied blends can be explained in terms of band conduction mechanisms, through band gap representation. The outcomes highlight the importance of new polymer blends uses as good candidates for ionic exchange membranes in industrial applications.