Paulo Ribeiro Claro

University of Aveiro | UA · Department of Chemistry

The effect of water on the physicochemical properties of deep eutectic solvents (DES) is a trending research topic. In this work, inelastic neutron scattering (INS) spectroscopy, was used to probe intermolecular interactions in the water-deep eutectic solvent mixtures for the cases of choline chloride (the hydrogen bond acceptor) and three differen...

The structure and dynamics of crystalline 4-(dimethylamino) benzaldehyde, 4DMAB, are assessed through INS spectroscopy combined with periodic DFT calculations. The excellent agreement between experimental and calculated spectra is the basis for a reliable assignment of INS bands. The external phonon modes of crystalline 4DMAB are quite well describ...

The dynamics of 2-methoxybenzaldehyde, 4-methoxybenzaldehyde, and 4-ethoxybenzaldehyde in the solid state are assessed through INS spectroscopy combined with periodic DFT calculations. In the absence of experimental data for 4-ethoxybenzaldehyde, a tentative crystal structure, based on its similarity with 4-methoxybenzaldehyde, is considered and ev...

Bacterial nanocellulose (BC)-based composites containing poly(2-hydroxyethyl methacrylate) (PHEMA), poly(methacroylcholine chloride) (PMACC) or poly(methacroylcholine hydroxide) (PMACH) were characterized by inelastic neutron scattering (INS) spectroscopy, combined with DFT (density functional theory) calculations of model systems. A reasonable mat...

The present work emphasizes the value of periodic density functional theory (DFT) calculations in the assessment of the vibrational spectra of molecular crystals. Periodic calculations provide a nearly one-to-one match between the calculated and observed bands in the inelastic neutron scattering (INS) spectrum of crystalline 4-phenylbenzaldehyde, t...

The present work aims at exploiting a polyelectrolyte nanocomposite based on poly(4-styrene sulfonic acid) (PSSA) and bacterial cellulose (BC) as an eco-friendly proton-exchange membrane (PEM) for application in microbial fuel cells (MFCs). The PSSA/BC-based PEM was confirmed as a true nanocomposite by inelastic neutron scattering (INS) vibrational...

There is a lack of fundamental knowledge on deep eutectic solvents, even for the most extensively studied mixtures, such as the mixture of cholinium chloride and urea, that prevents a judicious choice of components to prepare new solvents. The objective of this work is to study and understand the fundamental interactions between cholinium chloride...

A thorough vibrational portrait of 4-fluorobenzaldehyde is presented, covering Infrared (Mid- and Far-), Raman and Inelastic Neutron Scattering (INS) spectra. Periodic DFT calculations (CASTEP) of a model 4FB crystal proved useful for vibrational assignment, yielding estimates of experimental spectra with near one-to-one correspondence – including...

Montelukast (MLK), an oral antiasthmatic drug with growing use, requires special care in formulation and storage to avoid its degradation by action of light and/or water. This work investigates the increase in the stability of montelukast as the effect of molecular encapsulation with gamma-cyclodextrin (γ-CD) by means of a solvent-free method, cogr...

Widespread microplastic pollution is raising growing concerns as to its detrimental effects upon living organisms. A realistic risk assessment must stand on representative data on the abundance, size distribution and chemical composition of microplastics. Raman microscopy is an indispensable tool for the analysis of very small microplastics (<20 μm...

This work presents a comprehensive spectroscopic analysis of crystalline isoniazid, one of the main drugs in tuberculosis chemotherapy, using a blend of spectroscopic and computational methods. Mid- and far-infrared, Raman, and inelastic neutron scattering spectroscopies, with contribution of isotopic substitution are combined with discrete and per...

A thorough vibrational spectroscopy and molecular modeling study on poly(ethylene 2,5-furandicarboxylate) (PEF) explores its conformational preferences, in the amorphous and crystalline regions, while clarifying structure–property correlations. Despite the increasing relevance of PEF as a sustainable polymer, some of its unique characteristics are...

Seaweeds have been utilized by mankind for several hundreds of years, directly for food, medicinal purposes, and agriculture fertilizers. Today, seaweed is used in many countries for very different purposes: directly as food; as a source of phycocolloid extraction; for extraction of compounds with antiviral, antibacterial, or antitumor activity; an...

Seaweeds have been utilized by mankind for several hundreds of years, directly for food, medicinal purposes, and agriculture fertilizers. Today, seaweed is used in many countries for very different purposes: directly as food; as a source of phycocolloid extraction; for extraction of compounds with antiviral, antibacterial, or antitumor activity; an...

The solids choline chloride and urea, mixed in a 1:2 molar proportion, form the iconic deep eutectic solvent “Reline”. A combination of computational and vibrational spectroscopy tools, including inelastic neutron scattering (INS), have been used to probe intermolecular interactions in the eutectic mixture. Reline’s experimental spectra were estima...

This work provides an answer to the urge for a more detailed and accurate knowledge of the vibrational spectrum of the widely used analgesic/antipyretic drug commonly known as paracetamol. A comprehensive spectroscopic analysis - including infrared, Raman, and inelastic neutron scattering (INS) - is combined with a computational approach which take...

This chapter presents an overview of the application of Raman spectroscopy in the characterization of microplastics, opening with a brief description of the principles of Raman spectroscopy and some of its experimental apparatus, and discussing the main advantages and limitations of the technique. Particular attention is given to the location of pl...

Fronds of Gigartina pistillata exhibiting both tetrasporangial sori and cystocarps, i.e., producing tetraspores and carpospores (heterosporous thalli), were found in several rocky shores at the Portuguese northern coast. In order to clarify the nature and function of these reproductive structures, thalli of this species were collected and analyzed...

Carrageenan (E-407) and semirefined carrageenan (E-407a) are some of the main additives used by the food industry for their gelling, emulsifying, thickening, and stabilizing properties. These are natural ingredients that have been used for decades in food applications and are generally regarded as safe (GRAS). Worldwide, subtropical carrageenophyte...

A novel β-cyclodextrin (βCD) inclusion compound was prepared using 4-phenylpyridine-N-oxide (PPNO) as the organic guest. The inclusion compound, βCD·PPNO, was characterised both in solution and in the solid state using numerous techniques. 1H NMR in aqueous solution allowed the determination of a 1:1 stoichiometry and an association constant of 164...

The regular MCM-41 type mesostructured silica material was used as a support for the incorporation of the highly luminescent tris(beta-diketonate) complex Eu(tta)3ephen yielding the hybrid MCM-Eu material. Suitable characterization by powder X-ray diffraction (XRD), thermogravimetric analyses (TGA), diffuse reflectance infrared Fourier transform sp...

A systematic study of the interactions between water and alkyl methyl imidazolium chloride ionic liquids at 298.2 K, based on activity coefficients estimated from water activity measurements in the entire solubility range, is presented. The results show that the activity coefficients of water in the studied ILs are controlled by the hydrophilicity...

Phase-pure and highly crystalline [Ln(Hpmd)(H2O)] materials [where Ln3+ = Eu3+ (1), Gd3+ (2) and Tb3+ (3); H4pmd = 1,4-phenylenebis(methylene)diphosphonic acid] were prepared by using three distinct approaches: (i) conventional hydrothermal synthesis (180 °C, 3 days); (ii) microwave-assisted heating (50 W irradiation power, 40 °C, 5 seconds; nano-s...

The reaction of [MoO2Cl2(pzpy)] (1) (pzpy = 2-[3(5)-pyrazolyl]pyridine) with water in an open reflux system (16 h), in a microwave synthesis system (120 °C, 2 h), or in a Teflon-lined stainless steel digestion bomb (100 °C, 19 h) gave the molybdenum oxide/pyrazolylpyridine polymeric hybrid material [Mo3O9(pzpy)]n (2) as a microcrystalline powder in...

The inelastic neutron scattering (INS) spectra of cyclopentanone were obtained for pure and 50% CCl4 solution forms. Spectra are compared with infrared and Raman data, and with DFT calculated eigenvectors. This exercise aims to find spectroscopic evidence in the neutron spectra for the presence of C–H⋯O hydrogen bonds. These are weak interactions w...

Chiral porous inorganic materials, lanthanide pyrophosphates, were prepared from chiral porous metal-organic framework precursors, which upon thermal decomposition transpose their chirality and porosity onto the inorganic framework. It is argued that this synthesis concept may be extended to other chiral porous inorganic solids.

Following a computational-experimental approach, a highly luminescent β-diketonate-europium(III) complex containing 2-thenoyltrifluoracetonate (tta−) and 5,6-epoxy-5,6-dihydro-[1,10] phenanthroline (ephen) ligands, Eu(tta)3ephen (II), was theoretically studied by DFT/TD-DFT calculations, synthesized from Eu(tta)3(H2O)2(I) and fully characterized by...

β-Cyclodextrin (βCD) inclusion compounds of chloramphenicol in the solid-state were prepared via two different procedures, co-crystallisation from aqueous solution and the solvent-free method of co-grinding. Chloramphenicol inclusion into permethylated βCD (TRIMEB) was also performed by co-dissolution in ethanol. The co-crystallisation procedure wa...

Luminol, one of the most popular electrochemiluminescence systems used in forensic chemistry, proved to be a suitable system to study the importance of cooperativity in hydrogen-bond chains. The computational pairwise approach PiMM was applied to the system and a thorough band assignment was accomplished. Hydrogen-bond and hydrogen-bond cooperativi...

Polysaccharides present in several seaweeds (Kappaphycus alvarezii, Calliblepharis jubata, and Chondrus crispus—Gigartinales, Rhodophyta; Gelidium corneum and Pterocladiella capillacea—Gelidiales, Rhodophyta; Laurencia obtusa—Ceramiales, Rhodophyta; Himanthalia elongata, Undaria pinnatifida, Saccorhiza polyschides, Sargassum vulgare, and Padina pav...

The effects of implicitly considering the effects of hydrogen bonding on the molecular properties, such as vibrational frequencies, were inferred on the basis of DFT calculations. Several clusters of isopropylamine were assembled and theoretically characterized. The results showed that maximum H-bond cooperativity is achieved when the amine group a...

The complete vibrational spectra assignment of dihydrocoumarin is performed through a combined vibrational spectroscopy and DFT calculations approach. To provide effective information, vibrational analysis was also performed for α-pyrone and coumarin related systems. The presence of extra components in the νCO band profile can only be understood by...

Knowledge and control of the solid forms of active pharmaceutical ingredients are important aspects of drug development in the pharmaceutical industry. In this paper, the process of the molecular self-assembly of saccharin cocrystals and the 2-amino-5-methylpyridine salt of indomethacin, in terms of the hydrogen bonding patterns, has been studied i...

The present study reports a performance evaluation of the new Gaussian program version G09 relatively to the previous one in what concerns the SCRF formalism. The potential improvements achieved by changing program version and other SCRF defining parameters (like radii and SCRF models) were evaluated, by comparing the predicted values of several mo...

Introduction The estimation of the vibrational properties of large molecules by means of theoretical calculations is still a complex issue. Approaches such as strategy PIMM have provided good results for non-polymeric materials [1], but in the case of polymeric materials like Metal-Organic Frameworks (MOFs), this strategy is not usable. PIMM cannot...

The inclusion of phenylpyridine-N-oxide in β-CD yielded two different polymorphs which crystallise in either the triclinic P1 (phase I) or the monoclinic C2 (phase II) space groups. Both powdered and crystal forms of phase I readily transform into phase II, either by milling or spontaneously in open air after a few days.

Chloramphenicol was encapsulated in 1:1 proportion into the hosts βCD and TRIMEB by use of tailored methods to yield two solid products. Powder diffraction of these showed that βCD chloramphenicol is a new crystalline phase attributed to a true inclusion compound, while TRIMEB chloramphenicol is an amorphous glassy compound. Further characterisatio...

Inclusion complexes that comprise β-cyclodextrin (β-CD) and trimethyl(ferrocenylmethyl)ammonium iodide (1) have been prepared by codissolution of the host and guest in ethanol/water, accompanied by either conventional heating at 40 °C for 26 h (to give 2) or microwave-assisted heating for 30 min (to give 3). Solids were isolated and characterized b...

The paper describes a design strategy for the preparation of a novel inclusion compound (potassium4,4′-biphenyldicarboxylate⊂β-CD) suitable for use in supramolecular chemistry. In the first step the chemical feasibility of such an inclusion compound was evaluated by DFT calculations. Preliminary results revealed that two types of adducts are energe...

The asymmetric unit of the title compound, C(9)H(9)Br(3), is composed of a single molecule. Two bromo substituents are located on one side of the plane of the aromatic ring and the third is on the opposite side, with the molecular unit exhibiting an approximate noncrystallographic C(s) point group. The crystal structure is rich in Br...Br, CH(2)···...

The dioxomolybdenum(VI) complexes [MoO(2)Cl(2)(PzPy)] (1) and [MoO(2)(OSiPh(3))(2)(PzPy)] (5) (PzPy = 2-[3(5)-pyrazolyl]pyridine) were synthesized and characterized by vibrational spectroscopy, with assignments being supported by DFT calculations. Complex 5 was additionally characterized by single crystal X-ray diffraction. Recrystallization of 1 u...

Molecular orbital ab initio calculations have been performed on some triaza and tetraaza cyclic amines aiming at the determination of their minimum energy geometries and of the relative conformational energies in different protonation states. The results clearly show two factors governing the conformational preferences in these systems: the formati...

The title compound, C(2)H(8)NO(3)P, crystallizes in its zwitterionic form H(3)N(+)CH(CH(3))PO(O(-))(OH). In the crystal, the molecules are linked by N-H⋯O and O-H⋯O hydrogen bonds.

Spectroscopic evidence for C-H...O hydrogen bonding in chloroform...acetone [Cl(3)CH...O=C(CH(3))(2)] mixtures was obtained from vibrational inelastic neutron scattering (INS) spectra. Comparison between the INS spectra of pure samples and their binary mixtures reveals the presence of new bands at about 82, 130 and 170 cm(-1). Assignment of the 82...

The title salt, (C(5)H(6)N)(4)[Mo(2)Cl(2)O(5)(SO(4))(2)], comprises four pyridinium cations for each [(MoClO(2))(2)(μ-O)(μ-SO(4))(2)](4-) anionic unit. The asymmetric unit consists of three aggregates of the empirical formula. The tetra-anionic bimetallic molybdenum(VI) cluster is unprecedented and contains two sulfate and one oxide bridges. This s...

The supramolecular salt [H(2)pip](3)[Ge(hedp)(2)].14H(2)O (1) [H(2)pip(2+)=piperazine cation C(4)H(12)N(2)(2+); hedp(5-)=deprotonated form of etidronic acid, C(2)H(3)P(2)O(7)(5-)) is reported. This consists of an organic-inorganic hybrid hydrogen-bonded nanoporous framework, the internal surface of which acts as a template for the three-dimensional...

Unprecedented 3D interpenetrated networks of hydrogen-bonded water molecules and a hybrid matrix have been found in a novel supramolecular salt, [H2pip]3[Ge(hedp)2]⋅14 H2O (H2pip2+=C4H12N22+; hedp5−=C2H3P2O75−). In their Full Paper on page 7741 ff., J. Rocha et al. demonstrate that this “ice framework” is stable at ambient temperature for long peri...

In the title compound, (C5H6N)3[MoCl4O2]Cl, the pyridinium cations are N—H...Cl hydrogen bonded to the anionic [MoCl4O2]2− complexes and to the two crystallographically independent chloride anions (located on C2 axes). The Mo6+ centre adopts a highly distorted octahedral geometry, being surrounded by four chloride and two terminal oxide groups. The...

The asymmetric unit of the title compound, [Cu(2)(C(5)HF(6)O(2))(4)(C(11)H(9)NO)(2)], contains one half of the centrosymmetric dinuclear complex. The coordination geometry of the Cu(II) atom is octa-hedral, exhibiting a typical Jahn-Teller distortion. One trifluoro-methyl group is rotationally disordered between two orientations in a 1:1 ratio.

In the title compound, (C(5)H(6)N)(3)[MoCl(4)O(2)]Cl, the pyridinium cations are N-H⋯Cl hydrogen bonded to the anionic [MoCl(4)O(2)](2-) complexes and to the two crystallographically independent chloride anions (located on C2 axes). The Mo(6+) centre adopts a highly distorted octa-hedral geometry, being surrounded by four chloride and two terminal...

In the title complex, [Cu(C2H8N2)(2)(H2O)(2)](C13H9O2)(2)center dot 2.66H(2)O,the Cu-II centre (located at an inversion centre) is coordinated by two bidentate ethylenediamine (en) ligands and two water O atoms in a typical Jahn-Teller distorted octahedral geometry. The amino groups and the water molecules are disordered over two distinct crystallo...

In this work, the usefulness of the Pairs in Molecular Materials (PiMM) approach to elucidate unknown structures of molecular crystals is assessed. This methodology aims to assist the prediction of probable crystal structures from the vibrational spectra, through the identification of the most relevant motifs in the potential energy landscape of th...

Raman and infrared spectra of 3-aminobenzotrifluoride, in the liquid phase, and single vibronic level fluorescence spectra, in a supersonic jet, have been obtained and interpreted to give a fairly complete set of vibrational assignments in S0. These include the observation of the I20 band in fluorescence, where ν1 is the NH2-inversion vibration, in...