The First Metal Complexes of 4,6-diamino-1-hydro-5-hydroxy-pyrimidine-2-thione: Preparation, Physical and Spectroscopic Studies, and Preliminary Antimicrobial Properties

The new complexes [M2O5L2(H2O)2] · H2O (M = Mo, 1; M = W, 2), [RuL2(H2O)2] · H2O (3), [ML3] · xH2O (M = Rh, x = 2, 4; M = Ir, x = 1, 5), [RhL2(PPh3)2](ClO4) · 2H2O (6), [PdL2] · 2H2O (7), [PdL(phen)]Cl · H2O (8), [Re OL2(PPh3)]Cl (9) and [UO2L2] (10) are reported, where LH is 4,6-diamino-1-hydro-5-hydroxy-pyrimidine-2-thione. The complexes were characterized by elemental analyses, physical techniques (molar conductivity, room-temperature magnetic susceptibility), and spectroscopic (IR, Raman, UV/VIS/ligand field, NMR, mass) methods. The ligand L− is in its thione form and behaves as a bidentate chelate with the deprotonated (hydroxyl) oxygen and the nitrogen of one amino group as donor atoms. Oxobridged dinuclear (1, 2) and various mononuclear (3–10) structures are assigned for the complexes in the solid state. The metal ion coordination geometries are octahedral (1–6, 9, 10) or square planar (7, 8). The free ligand LH and complexes 1, 4, 7, and 8 were assayed in vitro for antimicrobial activity against two bacterial and two fungal cultures

Zn(II) and Cu(II)-based coordination polymers and metal organic frameworks by the use of 2-pyridyloximes and 1,3,5-benzenetricarboxylic acid.

The simultaneous use of 2-pyridyl oximes (pyridine-2 amidoxime, H2pyaox; 2-methyl pyridyl ketoxime, Hmpko) and 1,3,5-benzenetricarboxylic acid (H3btc) provided access to five new compounds, namely [Zn(H2btc)2(H2pyaox)2]¿2H2O (1¿2H2O), [Zn(Hbtc)(H2pyaox)2]n (2), [Cu(Hbtc)(H2pyaox)]n (3), [Cu(Hbtc)(HmpKo)]n (4) and [Cu2(Hbtc)2(Hmpko)2(H2O)2]¿4H2O (5¿4H2O). Among them, 3 is the first example of a metal-organic framework (MOF) containing H2pyaox. Its framework can be described as a 3-c uninodal net of hcb topology with the layers being parallel to the (1,0,1) plane. Furthermore, 3 is the third reported MOF based on a 2-pyridyl oxime in general. 2 and 4 are new members of a small family of coordination polymers containing an oximic ligand. 1-5 form 3D networks through strong intermolecular interactions. Dc magnetic susceptibility studies were carried out in a crystalline sample of 3 and revealed the presence of weak exchange interactions between the metal centres; the experimental data were fitted to a theoretical model with the fitting parameters being J = −0.16(1) cm−1 and g = 2.085(1). The isotropic g value was also confirmed by electronic paramagnetic resonance (EPR) spectroscopy. Reactivity studies were performed for 3 in the presence of metal ions; the reaction progress was studied and discussed for Fe(NO3)3 by the use of several characterization techniques, including single crystal X-ray crystallography and IR spectroscopy

Giant Heterometallic [Mn36Ni4]0/2− and [Mn32Co8] “Loops-of-Loops-and-Supertetrahedra” Molecular Aggregates

We report the synthesis, crystal structures and magnetic properties of the giant heterometallic [Mn36Ni4]2−/0 (compounds 1, 2)/[Mn32Co8] (compound 3) “loops-of-loops-and-supertetrahedra” molecular aggregates and of a [Mn2Ni6]2+ compound (cation of 4) that is structurally related with the cation co-crystallizing with the anion of 1. In particular, after the initial preparation and characterization of compound [Mn2Ni6(μ4-O)2(μ3-OH)3(μ3-Cl)3(O2CCH3)6(py)8]2+[Mn36Ni4(μ4-O)8(μ3-O)4(μ3-Cl)8Cl4(O2CCH3)26(pd)24(py)4]2− (1) we targeted the isolation of (i) both the cationic and the anionic aggregates of 1 in a discrete form and (ii) the Mn/Co analog of [Mn36Ni4]2− aggregate. Our synthetic efforts toward these directions afforded the discrete [Mn36Ni4] “loops-of-loops-and-supertetrahedra” aggregate [Mn36Ni4(μ4-O)8(μ3-O)4(μ3-Cl)8Cl2(O2CCH3)26(pd)24(py)4(H2O)2] (2), the heterometallic Mn/Co analog [Mn32Co8(μ4-O)8(μ3-O)4(μ3-Cl)8Cl2(μ2-OCH2CH3)2(O2CCH3)28(pd)22(py)6] (3) and the discrete [Mn2Ni6]2+ cation [Mn2Ni6(μ4-O)2(μ3-OH)4(μ3-Cl)2(O2CCH3)6(py)8](ClO4)(OH) (4). The structure of 1 consists of a mixed valence [Mn28IIIMn8IINi4II]2− molecular aggregate that contains two Mn8IIINi2II loops separated by two Mn6IIIMn4II supertetrahedral units and a [Mn2IIINi6II]2+ cation based on two [MnIIINi3II(μ4-O)(μ3-OH)1.5(μ3-Cl)1.5]4+ cubane sub-units connected through both mono- and tri-atomic bridges provided by the μ4-O2− and carboxylate anions. The structures of 2–4 are related to those of the compounds co-crystallized in 1 exhibiting however some differences that shall be discussed in detail in the manuscript. Magnetism studies revealed the presence of dominant ferromagnetic interactions in 1–3 that lead to large ground state spin (ST) values for the “loops-of-loops-and-supertetrahedra” aggregates and antiferromagnetic exchange interactions in 4 that lead to a low (and possibly zero) ST value. In particular, dc and ac magnetic susceptibility studies revealed that the discrete [Mn36Ni4] aggregate exhibits a large ST value ~ 26 but is not a new SMM. The ac magnetic susceptibility studies of the [Mn32Co8] analog revealed an extremely weak beginning of an out-of-phase tail indicating the presence of a very small relaxation barrier assignable to the anisotropic Co2+ions and a resulting out-of-phase ac signal whose peak is at very low T

Mononuclear and Dinuclear Manganese(II) Complexes from the Use of Methyl(2-pyridyl)ketone Oxime

The reactions of methyl(2-pyridyl)ketone oxime, (py)C(Me)NOH, with manganese(II) sulfate monohydrate have been investigated. The reaction between equimolar quantities of MnSO4 · H2O and (py)C(Me)NOH in H2O lead to the dinuclear complex [Mn2(SO4)2{(py)C(Me)NOH}4] · (py)C(Me)NOH, 1 · (py)C(Me)NOH, while employment of NaOMe as base affords the compound [Mn(HCO2)2{(py)C(Me)NOH}2] (2). The structures of both compounds have been determined by single crystal X-ray diffraction. In both complexes, the organic ligand chelates through its nitrogen atoms. The IR data are discussed in terms of the nature of bonding and the structures of the two complexes

From 1D coordination polymers to Metal Organic Frameworks by the use of 2-pyridyl oximes.

The synthesis and characterization of coordination polymers and metal-organic frameworks (MOFs) has attracted a significant interest over the last decades due to their fascinating physical properties, as well as their use in a wide range of technological, environmental, and biomedical applications. The initial use of 2-pyridyl oximic ligands such as pyridine-2 amidoxime (H2pyaox) and 2-methyl pyridyl ketoxime (Hmpko) in combination with 1,2,4,5-benzene tetracarboxylic acid (pyromellitic acid), H4pma, provided access to nine new compounds whose structures and properties are discussed in detail. Among them, [Zn2(pma)(H2pyaox)2(H2O)2]n (3) and [Cu4(OH)2(pma)(mpko)2]n (9) are the first MOFs based on a 2-pyridyl oxime with 9 possessing a novel 3,4,5,8-c net topology. [Zn2(pma)(H2pyaox)2]n (2), [Cu2(pma)(H2pyaox)2(DMF)2]n (6), and [Cu2(pma)(Hmpko)2(DMF)2]n (8) join a small family of coordination polymers containing an oximic ligand. 9 exhibits selectivity for FeIII ions adsorption, as was demonstrated by a variety of techniques including UV-vis, EDX, and magnetism. DC magnetic susceptibility studies in 9 revealed the presence of strong antiferromagnetic interactions between the metal centers, which lead to a diamagnetic ground state; it was also found that the magnetic properties of 9 are affected by the amount of the encapsulated Fe3+ ions, which is a very desirable property for the development of magnetism-based sensors

In search for molecules displaying ferromagnetic exchange: multiple-decker Ni12 and Ni16 complexes from the use of pyridine-2-amidoxime

The use of pyridine-2-amidoxime (pyaoxH2) in Ni chemistry has provided access to a dodecanuclear complex and a hexadecanuclear Ni cluster, namely [Ni12(pyaox)6(pyaoxH)6(MeOH)2Cl2]Cl4·5MeOH (1·5MeOH) and [Ni16(pyaox)8(pyaoxH)8(MeOH)4](SO4)4·10H2O·26MeOH (2·10H2O·26MeOH). Complex 1·5MeOH was isolated by the reaction of NiCl2·6H2O, pyaoxH2 and NaOMe in a 1 : 1 : 2 molar ratio in MeOH in 60% yield. Treatment of NiSO4·6H2O with pyaoxH2 and NEt3 in a 1 : 1 : 2 molar ratio in MeOH afforded 2·10H2O·26MeOH in good yield (65%). The two compounds display a multi-decker configuration based on stacked Ni4 layers, {Ni4(pyaox)2(pyaoxH)2}2+x (x = 3, 1·5MeOH; x = 4, 2·10H2O·26MeOH); each deck consists of two square planar and two octahedral NiII centres. The number of decks observed in 1·5MeOH and 2·10H2O·26MeOH depends on the nature of the inorganic anion that is present in the reaction system, which provides elements of synthetic control towards new high nuclearity NiII species. 2·10H2O·26MeOH is the first structurally characterized complex of any metal displaying a quadruple-decker configuration, being also the highest nuclearity metal cluster bearing pyaoxH2 and the highest nuclearity NiII cluster with any type of 2-pyridyl oxime. Each cluster cation displays ferromagnetic exchange between the octahedral NiII ions resulting in a spin ground state of S = 6 for 1 and S = 8 for 2. Magnetothermal studies have been performed and discussed for both clusters.CP and CE thank the School of Chemistry, NUI Galway, for the financial support. RI thanks the Royal Society of Edinburgh and ME thanks Spanish MINECO (MAT2015-68204-R) for funding. LCS acknowledges the financial support by FEDER (Fundo Europeu de Desenvolvimento Regional) through PT2020, by FCT (Fundação para a Ciência e a Tecnologia) for the research centre REQUIMTE/LAQV (UID/QUI/50006/2013) and for the grant SFRH/BPD/111899/2015.Peer Reviewe

A novel family of triangular CoII2LnIII and CoII2YIII clusters by the employment of Di-2-Pyridyl ketone

The synthesis, structural characterization and magnetic study of novel CoII/4f and CoII/YIII clusters are described. In particular, the initial employment of di-2-pyridyl ketone, (py)2CO, in mixed metal Co/4f chemistry, provided access to four triangular clusters, [CoII2MIII{(py)2C(OEt)(O)}4(NO3)(H2O)]2[M(NO3)5](ClO4)2 (M = Gd, 1; Dy, 2; Tb, 3; Y, 4), where (py)2C(OEt)(O)− is the monoanion of the hemiketal form of (py)2CO. Clusters 1-4 are the first reported Co/4f (1-3) and Co/Y (4) species bearing (py)2CO or its derivatives, despite the fact that over 200 metal clusters bearing this ligand have been reported so far. Variable-temperature, solid-state dc and ac magnetic susceptibility studies were carried out on 1-4 and revealed the presence of weak ferromagnetic exchange interactions between the metal ions (JCo-Co = +1.3 and +0.40 cm−1 in 1 and 4, respectively; JCo-Gd = +0.09 cm−1 in 1). The ac susceptibility studies on 2 revealed nonzero, weak out-of-phase (χ''M) signals below ~5 K

The sulfate ion as ligand in polynuclear complexes and coordination polymers of Mn, Co, Ni, Zn and Cd

The main target of this Thesis was the use of the Sulfate Ligand in the chemistry of polynuclear complexes and coordination polymers of transition metal ions. The sulfate ion is currently a ligand of great interest. Metal-sulfato complexes have been studied for their important roles in bioinorganic chemistry, in catalysis, in the field of porous-framework materials and in the chemistry of “cisplatin” analogues. The sulfate ion can act as terminal or bridging ligand and it can bridge up to ten metal centers, but in spite of this, a systematic structural analysis of metal-sulfato complexes is still lacking. For the above mentioned reasons, we decided to use the sulfate ligand for the synthesis of polynuclear and polymeric complexes. The organic ligands that we used for the synthesis of the compounds are shown below: The organic ligands which were studied in this Thesis are the ketone form of di-2 pyridyl ketone, the anion of the gem diol form of di-2 pyridyl ketone, methyl 2-pyridyl ketoxime, phenyl 2-pyridyl ketoxime and picolinic acid. Our group and others have explored the ternary reaction systems Μn+/X-/(py)2C(OH)O- or (py)2CO22- (Χ-= anionic ligands MeCO2-, SCN-, N3-, NO3-, PhCO2-). These “blends” foster the formation of discrete polynuclear metal systems and have led to the isolation of a variety of clusters with interesting structures and magnetic properties, including single-molecule magnetism. In this Thesis, we have modified one of the above mentioned binary “ligand blend” approaches. We have been exploring the use of the sulfato ligand, SO42-, instead of the N3-, NO3-, SCN-, MeCO2-, PhCO2- (X-) etc. ligands. The great coordinative flexibility and versatility of the (py)2CO-based anionic ligands, as well as the μ2, μ3, μ4, μ5 or μ10 potential of SO42-, prompted as to combine the two ligands to search for new types of clusters. The possible advantages of using SO42-, instead of the X- ligands mentioned above include (i) the possibility of triggering aggregation of preformed smaller species into new, higher-nuclearity products, and (ii) the possible diversion of known reaction systems developed using inorganic or organic monoanions to new species as a result of the higher charge and higher bridging capability of sulfates. In this Thesis metal sulfato complexes possessing the co-ligands methyl 2-pyridyl ketoxime and phenyl 2-pyridyl ketoxime have also been prepared and characterized. We were interested in studying the coordination chemistry of these ligands because their anionic form are versatile ligands for a variety of objectives, including μ2 and μ3 behavior, formation of polynuclear complexes (clusters), isolation of coordination polymers, mixed-metal chemistry and significant magnetic characteristics. The majority of the metal complexes of these ligands have been prepared only in the last years and much of their chemistry remains to be explored in detail.Βασικός στόχος της παρούσης Διατριβής είναι η χρησιμοποίηση του σουλφάτο υποκαταστάτη για τη σύνθεση πολυπυρηνικών συμπλόκων και πολυμερών ένταξης ορισμένων μετάλλων μετάπτωσης. Σουλφάτο μεταλλικά σύμπλοκα έχουν μελετηθεί για τον ρόλο που παίζουν στα πεδία της κατάλυσης, των πορωδών υλικών, των αναλόγων της ‘cis-πλατίνας’, στη Βιοανόργανη Χημεία, ενώ έχει αναφερθεί ότι σταθεροποιούν χημικές ενώσεις με δεσμούς PtΙΙΙ-PtΙΙΙ. Το θειϊκό ιόν μπορεί να δράσει ως τερματικός ή ως γεφυρωτικός υποκαταστάτης και έχει τη δυνατότητα να γεφυρώσει μέχρι και δέκα μεταλλικά κέντρα. Παρ’ όλα αυτά, ο αριθμός των δομικώς χαρακτηρισμένων μεταλλικών συμπλόκων με υποκαταστάτη το SO42- είναι μικρός. Οι οργανικοί υποκαταστάτες που χρησιμοποιήθηκαν στην εργασία αυτή για τη σύνθεση των συμπλόκων φαίνονται παρακάτω: Οι οργανικοί υποκαταστάτες που χρησιμοποιήθηκαν στην παρούσα Διατριβή είναι η κετονική μορφή της δι-2-πυρίδυλο κετόνης, το μονοανιόν της διολικής μορφής της δι-2-πυρίδυλο κετόνης, η μέθυλο 2-πυρίδυλο κετονοξίμη, η φαίνυλο 2-πυρίδυλο κετονοξίμη και το πικολινικό οξύ. Παλαιότερη ερευνητική εμπειρία του Εργαστηρίου μας, καθώς και άλλων ερευνητικών ομάδων, έδειξε ότι το τριαδικό σύστημα Μn+/X-/(py)2C(OH)O- ή (py)2CO22- (Χ-= οι ανιονικοί υποκαταστάτες MeCO2-, SCN-, N3-, NO3-, PhCO2-) έχει οδηγήσει σε σύμπλοκα με ενδιαφέρουσες δομές, σπάνιες πυρηνικότητες (π.χ. Μ7, Μ8, Μ9, Μ12, Μ14) και ενδιαφέρουσες μαγνητικές ιδιότητες (π.χ. υψηλού-σπιν μόρια). Tροποποιήσαμε το παραπάνω χημικό σύστημα εισάγοντας στη θέση των ανιονικών ανόργανων ή οργανικών υποκαταστατών Χ- (MeCO2-, SCN-, N3-, NO3-, PhCO2-), το θειϊκό ιόν. Η ποικιλία που διαθέτουν στους τρόπους ένταξης τόσο το μονοανιόν ή το διανιόν της διολικής μορφής της δι-2-πυρίδυλο κετόνης, όσο και το θειϊκό ιόν, μας έκανε να πιστεύουμε ότι, κατά την ταυτόχρονη εισαγωγή τους σε ένα χημικό σύστημα, είναι δυνατή η απομόνωση νέων πλειάδων με ενδιαφέροντες δομικούς τύπους και ιδιότητες. Επιπλέον, το SO42- διαθέτει διαφορετικό φορτίο και διαφορετικές δυνατότητες ένταξης, σε σχέση με τους παραπάνω ανιονικούς υποκαταστάτες Χ-, γεγονός που μας ώθησε να μελετήσουμε εάν και κατά πόσο αυτό επηρεάζει την ταυτότητα των προϊόντων. Επίσης, στην παρούσα εργασία μελετήσαμε σουλφάτο σύμπλοκα που περιέχουν δύο αντιπροσωπευτικές 2-πυρίδυλο οξίμες, τη μέθυλο 2-πυρίδυλο κετονοξίμη, (py)C(Me)NOH, και τη φαίνυλο 2-πυρίδυλο κετονοξίμη, (py)C(ph)NOH, ή τα ανιόντα αυτών, (py)C(Me)NO- και (py)C(ph)NO-, αντίστοιχα. Η διαφορά των δύο αυτών υποκαταστατών είναι η αντικατάσταση του ενός μεθυλίου του πρώτου υποκαταστάτη από έναν βενζολικό δακτύλιο στον δεύτερο. Οι οξίμες αποτελούν ιδανικούς υποκαταστάτες για την σύνθεση ομο- και ετερομεταλλικών πολυπυρηνικών συμπλόκων με ενδιαφέρουσες μαγνητικές ιδιότητες, και πολυμερών ένταξης. Σε αντίθεση με τις πολλές μελέτες που έχουν γίνει για τα μεταλλικά σύμπλοκα των απλών οξιμών και της σαλικυλικής αλδοξίμης, ελάχιστη έρευνα έχει πραγματοποιηθεί στη χημεία ένταξης των 2-πυρίδυλο οξιμών

Synthesis and Biomedical Applications of Highly Porous Metal–Organic Frameworks

In this review, aspects of the synthesis, framework topologies, and biomedical applications of highly porous metal–organic frameworks are discussed. The term “highly porous metal–organic frameworks” (HPMOFs) is used to denote MOFs with a surface area larger than 4000 m2 g−1. Such compounds are suitable for the encapsulation of a variety of large guest molecules, ranging from organic dyes to drugs and proteins, and hence they can address major contemporary challenges in the environmental and biomedical field. Numerous synthetic approaches towards HPMOFs have been developed and discussed herein. Attempts are made to categorise the most successful synthetic strategies; however, these are often not independent from each other, and a combination of different parameters is required to be thoroughly considered for the synthesis of stable HPMOFs. The majority of the HPMOFs in this review are of special interest not only because of their high porosity and fascinating structures, but also due to their capability to encapsulate and deliver drugs, proteins, enzymes, genes, or cells; hence, they are excellent candidates in biomedical applications that involve drug delivery, enzyme immobilisation, gene targeting, etc. The encapsulation strategies are described, and the MOFs are categorised according to the type of biomolecule they are able to encapsulate. The research field of HPMOFs has witnessed tremendous development recently. Their intriguing features and potential applications attract researchers’ interest and promise an auspicious future for this class of highly porous materials

Mn21Dy Cluster with a Record Magnetization Reversal Barrier for a Mixed 3d/4f Single-Molecule Magnet

International audienceA high-oxidation-state (Mn21DyIII)-Dy-III.IV cluster with an unusual structure is reported. It also possesses a record barrier to magnetization reversal for a 3d/4f single molecule magnet (SMM) and provides insight into how the full benefit of lanthanides to the mixed 3d/4f SMM field might be realized