Antonio Frontera

University of the Balearic Islands | UIB · Department of Chemistry

In recent years Pd(II) and Pt(II) cases have been reported wherein metals in square planar complexes were used as nucleophilic partners to construct supramolecular assemblies with electrophilic molecules like σ-hole and π-hole donors. The formation of such assemblies is based on the nucleophilicity and accessibility of the dz2 orbital (in group-10...

Two coordination compounds of Cu(II), namely, [Cu (phen)2Cl](NO3)·H2O (compound 1) and [Cu2(µ-Cl2)Cl2(Hdmpz)4] (compound 2), where phen = 1,10-phenanthroline and Hdmpz = 3,5-dimethylpyrazole, were synthesized at room temperature and characterized using elemental analysis, TGA, spectroscopic techniques (FT-IR and electronic) and single-crystal X-ray...

Unraveling the binding preferences involved in the formation of a supramolecular complex is key to properly understand molecular recognition and aggregation phenomena, which are of pivotal importance to biology. The halogenation of nucleic acids has been routinely carried out for decades to assist in their X-ray diffraction analysis. The incorporat...

Optically active luminescent materials based on lanthanoid ions attract significant attention due to their unique spectroscopic properties and the possibility of application as chemical sensors. Five isostructural lanthanoid metal organic...

A novel [3+2] cycloaddition reaction between 2-pyridylselenyl halides or trifluoroacetates and isocyanates is described herein. This new convenient methodology allows the synthesis of novel 3-oxo-1,2,4-selenodiazolium scaffolds, which are inaccessible by the known methods. The coupling proceeds efficiently for a broad scope of substrates under mild...

The application of halogen bonding in pharmaceutical chemistry remains a challenge. In this work, novel halogen-bonded cocrystals based on azole antifungal active pharmaceutical ingredients (APIs) and the ditopic molecule 1,4-diiodotetrafluorobenzene are reported. Their crystal structural features, spectroscopic properties, and thermal stability we...

This paper reports the synthesis and characterization of two closely related semicarbazone/thiosemicarbazone based organic compounds, N-(2-hydroxy-3-methoxy-5- methylbenzylidene)semicarbazide (1) and N-(2-hydroxy-3-methoxy-5-methylbenzylidene)thiosemicarbazide (2). Structural studies revealed the conformational diversity in these systems as compoun...

In this manuscript substituent effects in several silicon tetrel bonding (TtB) complexes were investigated at the RI-MP2/def2-TZVP level of theory. Particularly, we have analysed how the interaction energy is influenced by the electronic nature of the substituent in both donor and acceptor moieties. To achieve that, several tetrafluorophenyl silane...

This manuscript reports the synthetic protocol to obtain 3-substituted 4,5-dichloroisothiazole derivatives in good yields. This is exemplified by the synthesis of six new compounds, which have been spectroscopically characterized including their solid state structure by single crystal X-ray analysis. As substituents in position 3, both 1,4-dihydrop...

Pharmaceutical multicomponent solids have proved to efficiently modulate the physico-chemical properties of active pharmaceutical ingredients. In this context, polyphenols are interesting coformers for designing pharmaceutical cocrystals due to their wide safety profile and interesting antioxidant properties. The novel 6-propyl-2-thiouracil multico...

Two Zn(II) coordination polymers, viz., [Zn 2 Cl 2 (H 2 O) 2 (µ-4-AmBz) 2 ] n (1) and [ZnCl 2 (µ-3-AmPy) 2 ] n (2) (4-AmBz = 4-aminobenzoate, 3-AmPy = 3-aminopyridine) have been prepared at room temperature and characterized using elemental analysis, FT-IR, electronic spectroscopy, TGA (thermogravimetric analysis) and single crystal XRD. Crystal st...

Сo‐crystallization of 180°‐orienting s‐hole‐accepting tectons, namely 1,4‐diisocyanobenzene (1) and 1,4‐diisocyanotetramethylbenzene (2), with such homoditopic halogen bond donors as 1,4‐diiodotetrafluorobenzene (1,4‐FIB) and 4,4’‐diiodoperfluorobiphenyl (4,4’‐FIBP) afforded co‐crystals 1·1,4‐FIB, 1·4,4’‐FIBP, and 2·1,4‐FIB. Their solid‐state struc...

: It has been proposed that late transition metals with low coordination numbers (square planar or linear) can act as nucleophiles and participate in σ-hole interactions as electron donors. This is due to the existence, in this type of metal complexes, of a pair of electrons located at high energy d-orbitals (dz2 or dx2-y2), which are adequate for...

The reactivity of biological or synthetic metalloenzymes is modulated in the presence of redox innocent Lewis acidic metal ions as they change the redox potential of the redox active metal ions present in the active site of metalloenzymes. To study this effect, we synthesised a mono-nuclear V(IV) complex (VOL, 1) with an N2O4 donor bicompartmental...

C(sp3) atoms are known to act as electrophilic sites in self-assembly processes, and in all cases reported till now, they form only one interaction with nucleophiles; that is, they function as monodentate tetrel bond donors. This manuscript reports experimental (X-ray structural analysis) and theoretical evidence (DFT calculations), proving that th...

This manuscript reports the synthesis, spectroscopic and X-ray characterization of three new vanadium(V) complexes, namely [VO2L1] (1), (μ-O)2[V(O)(L2)2]·2CH3CN (2) and (μ-O)2[V(O)(L3)2]·CH3CN (3) [HL1 (2-ethoxy-6-((quinolin-8-ylimino)methyl)phenol), HL2 (2-(1-(2-(methylamino)ethylimino)propyl)phenol) and HL3 (2-(1-(2-(ethylamino)ethylimino)propyl)...

The importance of tetrel bonds (TtBs) in spontaneous self-assembly has been highlighted in two new lead(II) complexes: i.e. Pb[S2P{OC6H4(4-C(CH3)3)}2]2 (1) and Pb[S2P{OC6H4(4-C2H5)}2]2 (2), which were successfully isolated and characterized by FT-IR, UV–vis and multinuclear NMR (31P, 1H and 13C) spectroscopy. The structures of both complexes have b...

Two new Ni(II) and Co(II) coordination compounds,viz., [Ni(H2O)5(DMAP)](IPhth)·2H2O (1) and [Co(Hdmpz)4(H2O)2]Cl2 (2) (where DMAP = 4-dimethylaminopyridine, IPhth = Isophthalate, Hdmpz = 3,5-dimethylpyrazole),were synthesized and characterized using elemental analysis, TGA, spectroscopic (FTIR and electronic) and single crystal X-ray diffraction te...

Noncovalent interactions involving metals as electron acceptors are continuously under investigation. The term "matere bond" has been proposed to identify noncovalent donor-acceptor interactions where elements of group 7 of the periodic table play the role of the electrophilic site. Most of the works on matere bonds involve rhenium atoms usually in...

The series of substituted 1,2,4-selenodiazolium tetraphenylborate complexes were synthesized via cyclization between 2-pyridylselenylchloride, followed by the anion metathesis, and fully characterized. The utilization of tetraphenylborate anion, a strong π-electron donor via its phenyl rings, promoted the formation of assemblies exhibiting selenium...

Crystallization of [CuI(CNXyl)3] (1) with I2 (exhibiting strong halogen bond donor properties), at different molar ratios between the reactants, resulted in a series of (XylNC)CuI crystal polyiodides formed along with gradual accumulation of iodine, namely [Cu(I3)(CNXyl)3] (two crystalline polymorphs 2 I and 2 II), [Cu(I3)(CNXyl)3 ]•½I 2 (2•½I2), a...

A Cu(II)-based metal-organic framework (MOF) [Cu(muco)(3,5-DCP)]n (1) has been synthesized by using linear rigid aliphatic dicarboxylic acid, trans, trans-muconic acid (H2muco) and 3,5-dichloropyridine (3,5-DCP) as auxiliary ligand. The MOF adopts...

The chalcogen bond (ChB) is comparable to the hydrogen and halogen bonds both in terms of strengths and directionality. However, in contrast to the monovalent halogen atoms, usually the divalent...

A nickel(II)-zinc(II) complex, [(NiL)Zn(µ1,3-NCS)2]n (1) and a nickel(II)-mercury(II) complex, [{(NiL)Hg(µ1,3-SCN)(SCN)}2] (2) (where H2L = N,N'-bis(salicylidene)-1,3-propanediamine) have been synthesized via metalloligand approach of which former is a 2D coordination polymer but...

Two new dinuclear cobalt(II) complexes, [(H2O)CoIIL1 (μ-O 2 CR 1)Co II (NCS)] (1) and [(DMSO)CoIIL2(μ-O2CR2)CoII(NCS)] (2) {H2L1 = (2,2-dimethyl-1,3-propanediyl)bis(iminomethylene)bis(6-methoxyphenol); H2L2 = (2,2-dimethyl-1,3-propanediyl)bis(iminomethylene)bis(6-ethoxyphenol); R1CO2H= 3-methyl-4-nitrobenzoic acid; R2CO2H= 4-methyl-3-nitrobenzoic a...

In this paper combined experimental and theoretical results show that the occurrence of σ-hole interactions in catalytic systems extends to MTO. Four crystalline adducts between MTO and alyphatic and heteroaromatic bases are obtained and their X-ray analyses display short Re···N/O contacts opposite to both ORe and C-Re covalent bonds with geometrie...

This communication reports the synthesis and X-ray characterization of a new mononuclear aluminium compound exhibiting an intramolecular σ-hole triel bonding interaction. It is compared with a dinuclear aluminium compound, previously reported by us, where the aluminium atoms participate in two concurrent σ-hole triel bonding interactions. To our kn...

Metal ion interactions with nuclei acids and their constituents represent a multi-faceted and growing research field. This contribution deals with molecular recognition between synthetic purine 17 nucleosides and first-row transition metal complexes, with O-and/or N-amino chelators which are able to 18 engage in intra-molecular N-H···(N or O) and O...

A new hydrazone ligand, HL [(1-Methylimidazol-2-yl)methylene]isonicotinohydrazide has been synthesized and characterized by several spectroscopic methods. The ligand (HL) was then utilized for the preparation of two new complexes, namely, [Zn(L) 2 ]·2H 2 O (complex 1) and [Zn(H 2 L)Cl 3 ]·H 2 O(complex 2). The crystal structures of these complexes...

The chalcogen bond has been recently defined by the IUPAC as the attractive noncovalent interaction between any element of group 16 acting as an electrophile and any atom (or group of atoms) acting as a nucleophile. Commonly used chalcogen bond donor molecules are divalent selenium and tellurium derivatives that exhibit two σ-holes. In fact, the pr...

The simultaneous binding of a molecular entity through two interactions is a frequently pursued recognition mode due to the advantages it offers in securing molecular self-assembly. Here we report how the planarity of the benzothienoiodolium (BTI) cation allows for preorganizing in the cation plane the hydrogen, halogen, and chalcogen bonds (HB, XB...

This manuscript reports the synthesis and X-ray structures of three α,β "two wall" aryl-extended calix[4]pyrroles having either identical (symmetrically substituted) or different (non-symmetrically substituted) meso-aryl substituents (aryl = 4-ethynylphenyl and 4-iodophenyl). The X-ray structure of the co-crystal formed by the two symmetrically sub...

Dithiolate-amine binary ligand systems based two novel supramolecular structures of Ni(II) coordination compounds [Ni(2-ap)2(i-mnt)] (1) and [Ni2(i-mnt)2(tn)2]n (2) [where i-mnt⁻²: 1,1-dicyanoethylene-2,2-dithiolate, 2-ap: 2-amino pyridine, tn: 1,3-diaminopropane] have been designed, synthesized and characterized by spectroscopic techniques and X-r...

Two linear mixed-valence trinuclear centrosymmetric cobalt(III)-cobalt(II)-cobalt(III) complexes, [CoII{(μ-L¹)(μ-OOCCH2COOH)CoIII(DMF)}2](ClO4)2⋅2DMSO (1) and [CoII{(μ-L²)(μ-OOCCH2COOH)CoIII(DMF)}2](ClO4)2⋅2DMSO (2) have been synthesized using tetradentate N2O2 donor 'reduced Schiff base' ligands, H2L¹ (2,2-dimethyl-1,3-propanediyl)bis(iminomethyle...

A new 1D coordination polymer (CP), [(SCN)Cd(L¹)Pb(NCS)]n (1) was synthesized using N2O4-based Scaffold (H2L¹ = N, N’-bis(3-methoxysalicylidenimino)-1,3-diaminopropane) and structurally characterized using various analytical instruments. X-ray structure disclosed complex (1) crystallize in the Orthorhombic space group P212121 with Z=4. The crystal...

Two new coordination compounds of Mn(II) and Cu(II) involving 2,6-pyridinedicarboxylate viz. [Mn3(2,6-PDC)4(H2O)4][Mn(H2O)6]·8H2O (1) and [Cu(2,6-PDC)(H2O)(4-CNpy)]·H2O (2) (2,6-PDC = 2,6-pyridinedicarboxylate, 4-CNpy = 4-cyanopyridine) have been synthesized at room temperature. Compound 1 crystallizes as a co-crystal hydrate of Mn(II); whereas com...

In this article, we describe the serendipitous synthesis of two remarkable iso-structural Cd(ii)-Salen complexes [L2Cd4(OAc)2(NCS)2] in the presence of H2L and NaSCN {where L = L1 (N,N'-bis(3-methoxysalicylidene)-1,2-diaminopropane) and L = L2 (N,N'-bis(3-methoxysalicylidene)-ethylenediamine) in 1 and 2, respectively}. The complexes were characteri...

The series of benzylic-substituted 1,2,4-selenodiazolium salts were prepared via cyclization reaction between 2-pyridylselenyl chlorides and nitriles and fully characterized. Substitution of the Cl anion by weakly binding anions promoted the formation supramolecular dimers featuring four center Se2N2 chalcogen bonding and two antiparallel selenium·...

Four new Cu(II)-based hexagonal complexes with the metallomacrocycle formulae [Cu6(5-nip)6(3-py)6(H2O)12] (1), [Cu6(5-nip)6(3-Clpy)6(H2O)12] (2), [Cu6(5-nip)6(3-Brpy)6(H2O)12] (3), and [Cu6(5-nip)6(3-Ipy)6(H2O)12] (4) have been synthesized using 5-nitroisophthalic acid (H25-nip) and pyridine (py)/3-halopyridine (3-Xpy; X = Cl, Br, and I) ligands. T...

In this manuscript we report the synthesis and structural characterization of five pyrimidine amino acid/peptide modified derivatives: N-(2-pyrimidyl)-β-alanine (pyr-β-Ala) (1), N-(2-pyrimidyl)-γ-aminobutiric (pyr-GABA) (2), N-(2-pyrimidyl)-5-aminovaleric (pyr-5A-Val) (3), N-(2-pyrimidyl)-6-aminohexanoic (pyr-6A-Hex) (4) and N-(2-pyrimidyl)glycylgl...

Thiophenyl-isonicotinohydrazide, a multidentate Schiff base, acts as a tridentate N,O,N donor out of which N,O-chelates to one Zn(II) and pyridyl-N links to the adjacent Zn(II) to constitute a 2D coordination polymer, {[Zn(SIZ)2].DMF}n (CP1) (HSIZ = (E)-N'-(thiophen-2-ylmethylene)isonicotinohydrazide, DMF=N,N-Dimethylformamide). The CP1 has been ch...

A dinuclear oxo-bridged vanadium(V) Schiff base complex, (µ-O)2[V(O)(L)]2 , [where HL= 2-((2-aminocyclohexylimino)methyl)-6-ethoxyphenol] has been synthesized and further characterized with standard spectroscopic methods. Structure of the complex has been determined with the help of single crystal X-ray diffraction study. The complex consists of tw...

Two new coordination compounds of Zn(II) involving cyanopyridine ligands viz. [Zn(2,6-PDC)(3-CNpy)(H2O)2] (1) and [Zn(4-CNpy)2Cl2] (2) (2,6-PDC = 2,6-pyridinedicarboxylate, 3-CNpy = 3-cyanopyridine, 4-CNpy = 4-cyanopyridine) have been synthesized and characterized using elemental analysis, TGA, spectroscopic (FT-IR, electronic and ¹H-NMR) technique...

Lanthanide coordination polymers (Ln-CPs) are potential chemosensors when fabricated to depict a detectable change in optical properties on interaction with target analytes. This work investigates the interaction of nitroaromatic compounds with Ln-CPs leading to induced changes in fluorescence emission intensity, a crucial strategy to develop a sel...

A hyperresponsive tool to assess supramolecular catalysis, the cyclization of di‐epoxides into cyclic ethers is used to elucidate the difference between pnictogen‐bonding and Lewis acid catalysis systematically. For all stereoisomers, most tested catalysts follow the Baldwin rules. Brønsted acid and anion‐π catalysis afford almost only Baldwin prod...

The essential role of organic crystals in drug development represents a significant research area and remains enduringly topical within the pharmaceutical industry. In the present study, four cyclic aminobenzonitriles 3a-d were prepared through the nucleophilic aromatic substitution reaction of 4-fluorobenzonitrile with various cyclic amines. The s...

Four co-crystals involving dicarboxylic acids and pyridine derivatives, viz. (ox)0.5(2-CNpy) (1), (adp)(4-CNpy)2 (2), (tp)(4-CNpy)2 (3) and (adp)(3-CNpy)2 (4) (ox = oxalic acid, tp = terephthalic acid, adp = adipic acid, CNpy = cyanopyridine), have been synthesized at room temperature in water medium. Crystal-structure analysis of co-crystal 1 reve...

The term matere bond has been recently used to refer to an attractive noncovalent interaction between any element of group 7 acting as an electrophile and any atom (or group of atoms) acting as a nucleophile. The utilization of metals such as σ-hole donors is starting to attract the attention of the scientific community. In this manuscript, a compa...

Identifying and characterizing new binding events between electron donor and acceptor counterparts represents a crucial step to complete the molecular recognition and aggregation picture, which is key to chemistry and biology. In this study we interrogated both the PDB (Protein Data Bank) and CSD (Cambridge Structural Database) for the presence of...

A simple 1:1 cadmium (II) complex CdCl2L of 4´-[4-(4-aminophenyl)phenyl]- 2,2′:6′,2"-terpyridine ligand L was synthesized, and structure was established by ¹H NMR and single-crystal X-ray diffraction study. The crystal structure revealed that Cd(II) ion in the complex adopted a distorted trigonal bipyramidal geometry, and coordinated to three nitro...

The co‐crystallization of tetracyanobenzene (TCB) with haloarenes ArX provided six new co‐crystals TCB•ArX (ArX = PhCl, PhBr, 4‐MeC 6 H 4 Cl, 4‐MeC 6 H 4 Br, 4‐MeOC 6 H 4 Cl, 1,2‐Br 2 C 6 H 4 ) which were studied by X‐ray diffraction. In these systems, the strong collective effect of π⋯π stacking interactions and lone pair‐(X)⋯π‐hole‐(C) bondings b...

A discrete π-hole···σ-hole dimer is synthesized and X-ray characterized. It presents a perfect thumbtack geometry where the σ-hole of the linear [AuI2]- anion points to the π-hole located above the central Au-atom of the [AuI4]- anion. Such discrete π-hole···σ-hole dimers are unprecedented in literature, since all mixed-valence gold(I/III) iodide c...

The synthetic protocol and solid state characterization of two new coumarin‐pyrazolylthiazole hybrids (1‐2) are detailed in this manuscript. Synthesized compounds were characterized applying nuclear magnetic resonance, Fourier‐transform infrared spectroscopy and single‐crystal X‐ray diffraction techniques. A detailed structural analysis of 3‐(2‐(5‐...

Two new copper (II) carboxylates viz. [Cu 2 (μ-2-chlorobenzoato-O,O') 4 (2-methoxybenzaldehyde) 2 ] (1) and [Cu(μ-3,5-dinitrobenzoato-CO,O)(μ-3,5-dinitrobenzoato-NO,O)][Cu 2 (μ-3,5-dinitrobenzoato-CO,O′)](μ 1 MeOH) 2 (2) containing 2-chlorobenzoic acid and 3,5-dinitrobenzoic acid respectively were synthesized, and characterized by elemental analyse...

The synthesis of two gold(I) complexes containing a pyridyl ligand with a polyethylenglycol pendant arm at one position and a chromophore (aniline, for compound 3 or coumarine, for compound 4)...

The dichalcogenides Ph2Ch2 (Ch = S, Se, Te) were cocrystallized with the perfluorinated chalcogen bond donors TolF2Te and PyF2Te (TolF = 4-CF3C6F4, PyF = 4-NC5F4) to give the 1:1 cocrystals...

Osme bonds have been recently defined as the attractive interaction between an element of group 8 acting as an electrophile and any atom or group of atoms acting as a nucleophile. To date, the known examples of osme bonds in X-ray structures involve mostly the highly reactive OsO4 and amines and amine oxides. In this work, evidence supporting the e...

Three coordination complexes {[Cu(pydco)(pz)0.5(H2O)]·H2O}n (1), [Cu(pydco)(phen)(H2O)]·2H2O (2), and [Zn2(pydco)(phen)2Cl2]·2H2O (3) have been synthesized at room temperature using a mixed-ligand system including pyridine-2,6-dicarboxylic acid N-oxide (H 2 pydco) as O-donor as well as pyrazine (pz) and 1,10-phenanthroline (phen) as N,N'-bidentate...

Squaraines are 1,3-disubstituted squaric acid derivatives featuring intense fluorescence in the visible. Unlike their parent compounds, N-squaraines obtained by condensation reaction between squaric acid and primary anilines are non-fluorescent compounds. The incorporation of electron-withdrawing substituents in the para position of the phenyl ring...

A typical halogen bond (HaB) donor, 1,4-dibromo-2,3,5,6-tetrafluorobenzene (FBB), was cocrystallized with the isocyanide CNMes and the cyanide NCMes to give two isostructural cocrystals, (CNMes)·FBB and (NCMes)·FBB. Their solid-state architecture exhibits a close similarity between the isocyanide and cyanide groups in their HaB-accepting role. This...

Mononuclear aryldithiophosphates of indium(III), In[S2P{OAr}2]3 ; Ar = (3,5-CH3)2C6H3 (1), (3,4-CH3)2C6H3 (2), (2,5-CH3)2C6H3 (3) and (2,4-CH3)2C6H3 (4), have been synthesized and characterized by elemental analysis, NMR and FT-IR spectroscopy. Single crystal X-ray crystallography reveals that complex 1 belongs to the monoclinic crystal system with...

We report high-level ab initio calculations (CCSD(T)(full)/CBS//SCS-RI-MP2(full)/augcc- pwCVTZ) that demonstrate the importance of cooperativity effects when Anion–π and CH/π interactions are simultaneously established with benzene as the π-system. In fact, most of the complexes exhibit high cooperativity energies that range from 17% to 25.3% of th...

Two new dinuclear coordination compounds viz. [Cu2(μ-fum)(phen)2(H2O)6](fum)·6H2O (1) and [Mn2(μ-phth)2(phen)4]·2H2O (2) (phen = 1,10-phenanthroline, fum = fumarate and phth = phthalate) have been synthesized and characterized by elemental analysis, single crystal X-ray diffraction studies, electronic, vibrational, and ¹H-NMR spectroscopy and therm...