Molecular compounds metal chalcogenides: synthesis, characterization and study of their solution chemistry

The present Ph.D. Thesis is related to metal chalcogenides materials and is divided into two parts. The first part deals with the synthesis, structural characterization and study of the solution chemistry of soluble metal-chalcogenide anions including [ΜQ4]4-, [Μ2Q6]4- and [Μ4Q10]4- (M= Ge, Sn, Q=S, Se). These anionic groups have been recently utilized as building blocks for the construction of novel mesostructured materials. However, their complex solution chemistry greatly affects the quality and properties of the final solid materials and therefore speciation analysis of the precursor solution is of paramount importance not only for understanding how these system forms but also to design and systematic develop new, chalcogenides-based nanostructured materials with improved properties. We have studied the stability of the above anions towards oligomerization and/or dissociation reactions in aqueous and formamide solutions using electron spray mass spectrometry ESI-MS, 119Sn NMR, 77Se NMR and 119Sn Mossbauer spectroscopy. The combination of all these techniques was applied for the first time in an effort to elucidate the complex solution equilibria. In the case of [Ge4S10]4- anions in aqueous solution, we have indentified for the first time the new anion [Ge(OH)3S]-. The formation of this anion is accelerated upon heating of the solution at 80 oC and exposure to atmosphere. In the case of [SnSe4]4- anions, their aqueous solution chemistry is greatly affected by the concentration and the pH. In particular, while at high concentration and high pH these anions are stable, at low concentration and near neutral pH, an almost quantitative dimerization that affords [Sn2Se6]4- anions, was observed. In more complex systems such as mixtures of [SnSe4]4- and [Sn2Se6]4- anions, we indentified for the first time the anions [SnSe3]2-. The second part of the Ph.D. Thesis deals with the solvothermal synthesis and structural characterization of novel crystalline metal-chalcogenides using organic molecules (mainly amines) as structure directing agents (templates). In particular, solvothermal reactions were performed at 200 oC under pressure using parr reactors. The atomic structure of seven (7) new, crystalline materials in the systems Sn/Se, Zn/Sn/Se, and M/Ge/Se (M=Zn, Mn) was determined using single-crystal X-ray diffractometry. In addition, all materials were fully characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (SEM/EDS), powder X-ray diffraction (PXRD), 119Sn Mossbauer, IR and Raman spectroscopy and 3 thermogravimetry analysis (TGA). Finally, their optical properties were studied using solid-state, diffuse reflectance UVvis/ near-IR spectroscopyΗ παρούσα διδακτορική διατριβή αναφέρεται στην σύνθεση και των χαρακτηρισμό ενώσεων μετάλλου χαλκογονιδίου. Συγκεκριμένα, η διατριβή χωρίζεται σε δύο ενότητες. Η πρώτη ενότητα αναφέρεται στη μελέτη διαλυτών ανιοντικών ομάδων όπως [MQ4]4-, [M2Q6]4- και [M4Q10]4- (M=Ge, Sn, Q=S, Se), χρησιμοποιώντας τεχνικές φασματομετρίας μάζας ESI-MS, 119Sn NMR, 77Se NMR και φασματοσκοπία 119Sn Mossbauer. Στόχος της συγκεκριμένης ενότητας αποτελεί ο ειδοπροσδιορισμός (speciation) των διαφόρων ειδών στο διάλυμα τα οποία προκύπτουν από την διάλυση πρόδρομων αλάτων όπως Α4MQ4, A4Μ2Q6 και A4M4Q10 (όπου A=Na+, K+ ή (CH3)4N+). Ο συνδυασμός των παραπάνω τεχνικών εφαρμόζεται για πρώτη φορά και έρχεται να αντιμετωπίσει την αρκετά πολύπλοκη χημεία των σχετικών ανιόντων τα οποία τονίζεται ότι έχουν χρησιμοποιηθεί πρόσφατα ως δομικές μονάδες για την ανάπτυξη καινοτόμων νανοδομημένων ημιαγώγιμων στερεών. Η ειδοταυτοποίηση των διαφόρων μοριακών ειδών στο διάλυμα θα βοηθήσει σημαντικά στον συστηματικό και όχι τον εμπειρικό σχεδιασμό νανοδομημένων στερεών. Στόχος αποτελεί η δυνατότητα σχεδιασμού νέων υλικών με επιθυμητές ιδιότητες και εφαρμογές. Η δεύτερη ενότητα αναφέρεται στην σύνθεση και τον χαρακτηρισμό νέων κρυσταλλικών στερεών με βάση τα χαλκογονίδια (S, Se), χρησιμοποιώντας οργανικά μόρια (κυρίως αμίνες) ως περιγράμματα δομής (templates). Συγεκριμένα, πραγματοποιήθηκαν διαλυτο-θερμικές (solvo-thermal) αντιδράσεις σε σχετικά χαμηλές θερμοκρασίες (200 oC) υπό πίεση. Η κρυσταλλική δομή επτά (7) νέων ενώσεων προσδιορίστηκε με περίθλαση ακτίνων-Χ από μονοκρύσταλλο. Επιπλέον, ο πλήρης χαρακτηρισμός της μορφολογίας και της δομής των συγκεκριμένων στερεών πραγματοποιήθηκε με ηλεκτρονική μικροσκοπία σάρωσης (SEM/EDS), περίθλαση ακτίνων-Χ σε δείγματα σκόνης, φασματοσκοπία 119Sn Mossbauer, IR, Raman και θερμική ανάλυση, ενώ οι οπτικές ιδιότητες μελετήθηκαν με φασματοσκοπία διάχυτης ανακλαστικότητας (UV-vis/near IR) σε στερεά κατάσταση. Λέξεις κλειδιά: χαλκογονίδια, ημιαγωγοί, ειδοπροσδιορισμός, ηλεκτροψεκασμός σε συνδυασμό με φασματομετρία μάζας, υβριδικά στερε

Heptanuclear lanthanide [Ln7] clusters: from blue-emitting solution-stable complexes to hybrid clusters

The use of LH3 (2-(β-naphthalideneamino)-2-hydroxymethyl-1-propanol) and aibH (2-amino-isobutyric acid) in 4f chemistry has led to the isolation of eight new isostructural lanthanide complexes. More specifically, the reaction of the corresponding lanthanide nitrate salt with LH3 and aibH in MeOH, under solvothermal conditions in the presence of NEt3, led to the isolation and characterization of seven complexes with the general formulae [LnIII7(OH)2(L′)9(aib)]·4MeOH (Ln = Gd, 1·4MeOH; Tb, 2·4MeOH; Dy, 3·4MeOH; Ho, 4·4MeOH; Er, 5·4MeOH; Tm, 6·4MeOH; Yb, 7·4MeOH L′ = the dianion of the Schiff base between naphthalene aldehyde and 2-amino-isobutyric acid). Furthermore, the isostructural YIII analogue, cluster [YIII7(OH)2(L′)9(aib)]·4MeOH (8·4MeOH), was synthesized in a similar manner to 1–7. The structure of all eight clusters describes a distorted [MIII6] octahedron which encapsulates a seventh MIII ion in an off-centre fashion. Dc magnetic susceptibility studies in the 5–300 K range for complexes 1–7 reveal the presence of dominant antiferromagnetic exchange interactions within the metallic clusters as evidenced by the negative Weiss constant, θ, while ac magnetic susceptibility measurements show temperature and frequency dependent out-of-phase signals for the [DyIII7] analogue (3·4MeOH), suggesting potential single molecule magnetism character. Furthermore, for complex 1, simulation of its dc magnetic susceptibility data yielded very weak antiferromagnetic interactions within the metallic centres. Solid-state emission studies for all 1–8 clusters display ligand-based emission, while extended 1D and 2D NMR studies for 8·4MeOH reveal that the species retain their structural integrity in solution. In addition, TGA measurements for 1, 3 and 7 revealed excellent thermal stability up to 340 °C for the clusters

Employment of a new tripodal ligand for the synthesis of cobalt(II/III), nickel(II), and copper(II) clusters: magnetic, optical, and thermal properties

The employment of 2-(β-naphthalideneamino)-2-(hydroxymethyl)-1-propanol (LH3) in cobalt, nickel, and copper chemistry has led to the isolation of five new metallic complexes with interesting magnetic properties. More specifically, the reaction of Co(OAc)2·4H2O with LH3 in MeOH in the presence of NEt3 under solvothermal conditions forms the complex [CoIII2CoII3(L)2(LH)2(L′)(OAc)]·8.5MeOH (1·8.5MeOH; L′ = monoanion of 2-hydroxy-1-naphthaldehyde), while in nickel chemistry, a similar reaction of Ni(OAc)2·6H2O with LH3 in MeCN in the presence of NEt3 under high pressure/temperature forms the complex [NiII(LH2)2]·2MeCN (2·2MeCN). Repeating the same reaction in MeOH and switching from Ni(OAc)2·4H2O to NiSO4·4H2O produces the complex [NiII4(HL)3(OMe)(MeOH)3](SO4)0.5·2MeOH (3·2MeOH) under solvothermal conditions. Furthermore, in copper chemistry, the reaction of Cu2(OAc)4·2H2O with LH3 in the presence of NEt3 in MeOH under solvothermal conditions affords the complex [CuII4(LH)4] (4), while the same reaction under ambient temperature and pressure conditions forms [CuII4(LH)4] ·3.5MeOH·2.25H2O (5·3.5MeOH·2.25H2O). Complex 1 is a mixed-valent [CoIII2CoII3] complex, consisting of three edge-sharing [Co3] triangles. Complex 2 is a nickel(II) monomer in which the central metal is found in an octahedral geometry, while complex 3 describes a [NiII4] cubane. Complexes 4 and 5 may be considered as structural isomers because they possess the same formulas but different topologies: 4 describes a highly distorted [CuII4(OR)4]4+ eight-membered ring, while 5 consists of a distorted [CuII4(μ3-OR)4]4+ cubane. In addition, 5 can be converted to 4 in excellent yield under solvothermal conditions. Direct-current magnetic susceptibility studies have been carried out in the 5–300 K range for complexes 1 and 3–5, revealing the possibility of a high-spin ground state for 1, an S = 4 ground state for 2, and diamagnetic ground states for 4 and 5

Application of Ultraviolet-Visible Absorption Spectroscopy with Machine Learning Techniques for the Classification of Cretan Wines

The present study was aimed at the identification, differentiation and characterization of red and white Cretan wines, which are described with Protected Geographical Indication (PGI), using ultraviolet–visible absorption spectroscopy. Specifically, the grape variety, the wine aging process and the role of barrel/container type were investigated. The combination of spectroscopic results with machine learning-based modelling demonstrated the use of absorption spectroscopy as a facile and low-cost technique in wine analysis. In this study, a clear discrimination among grape varieties was revealed. Moreover, a grouping of samples according to aging period and container type of maturation was accomplished, for the first time

A strongly blue-emitting heptametallic [DyIII7] centered-octahedral single-molecule magnet

The employment of 2-(β-naphthalideneamino)-2-(hydroxymethyl)-1-propanol and 2-aminoisobutyric acid in dysprosium chemistry has led to the isolation of a novel heptanuclear [DyIII7] cluster displaying single-molecule-magnetism behavior and blue-emitting properties

Photodegradation of Pyrene on Al 2 O 3 Surfaces: A Detailed Kinetic and Product Study

International audienc

Verifying the Geographical Origin and Authenticity of Greek Olive Oils by Means of Optical Spectroscopy and Multivariate Analysis

Olive oil samples from three different Greek regions (Crete, Peloponnese and Lesvos) were examined by optical spectroscopy in a wide spectral region from ultraviolet to near infrared using absorption, fluorescence and Raman spectroscopies. With the aid of machine learning methods, such as multivariate partial least squares discriminant analysis, a clear classification of samples originating from the different Greek geographical regions was revealed. Moreover, samples produced in different subareas of Crete and Peloponnese were also well discriminated. Furthermore, mixtures of olive oils from different geographical origins were studied employing partial least squares as a tool to establish a model between the actual and predicted compositions of the mixtures. The results demonstrated that optical spectroscopy combined with multivariate statistical analysis can be used as an emerging innovative alternative to the classical analytical methods for the identification of the origin and authenticity of olive oils

Mineral Oxides Change the Atmospheric Reactivity of Soot: NO 2 Uptake under Dark and UV Irradiation Conditions

International audienc

An indeno-quinoxaline based oxime ligand for the synthesis of polynuclear Ni(ii) clusters

The reaction of Ni(OAc)2·4H2O with LH (LH = 11H-indeno[1,2-b]quinoxalin-11-one oxime) in a mixture of solvents comprising MeCN/MeOH (1 : 1) under solvothermal conditions in the presence of NEt3 forms the complex [Ni3(L)5(OAc)(MeOH)]·2.6MeCN·0.7MeOH·0.2H2O (1·2.6MeCN·0.7MeOH·0.2H2O) in moderate yield. Repeating the reaction in MeOH produces the complex [Ni6(L)6(OAc)4(OMe)2]·1.5MeOH·1.3H2O (2·1.5MeOH·1.3H2O) in good yield, while the reaction between Ni(ClO4)2·6H2O and LH in the presence of NEt3 in MeOH under solvothermal conditions yields complex [Ni5(L)6(OMe)2(OH)(H2O)2(MeOH)2](ClO4)·8.8MeOH·1.4H2O (3·8.8MeOH·1.4H2O). Furthermore, the reaction between Ni(ClO4)2·6H2O, LH and 2-amino-isobutyric acid, aibH, in MeCN in the presence of NEt3 forms complex [Ni7(L)7(aib)4(OH)(MeCN)0.5(H2O)0.5](ClO4)2·4MeCN·0.25H2O (4·4MeCN·0.25H2O) under high temperature/pressure, while the same reaction in MeOH yields complex [Ni8(L)8(aib)3(OMe)3](ClO4)2·0.75MeOH·4.2H2O (5·0.75MeOH·4.2H2O). Variable temperature dc magnetic susceptibility studies show that all 1–5 clusters display a small or a diamagnetic ground-state, S

Employment of a New Tripodal Ligand for the Synthesis of Cobalt(II/III), Nickel(II), and Copper(II) Clusters: Magnetic, Optical, and Thermal Properties

The employment of 2-(β-naphthalideneamino)-2-(hydroxymethyl)-1-propanol (LH₃) in cobalt, nickel, and copper chemistry has led to the isolation of five new metallic complexes with interesting magnetic properties. More specifically, the reaction of Co­(OAc)₂·4H₂O with LH₃ in MeOH in the presence of NEt₃ under solvothermal conditions forms the complex [Co^III₂Co^II₃(L)₂(LH)₂(L′)­(OAc)]·8.5MeOH (<b>1</b>·8.5MeOH; L′ = monoanion of 2-hydroxy-1-naphthaldehyde), while in nickel chemistry, a similar reaction of Ni­(OAc)₂·6H₂O with LH₃ in MeCN in the presence of NEt₃ under high pressure/temperature forms the complex [Ni^II(LH₂)₂]·2MeCN (<b>2</b>·2MeCN). Repeating the same reaction in MeOH and switching from Ni­(OAc)₂·4H₂O to NiSO₄·4H₂O produces the complex [Ni^II₄(HL)₃(OMe)­(MeOH)₃]­(SO₄)_0.5·2MeOH (<b>3</b>·2MeOH) under solvothermal conditions. Furthermore, in copper chemistry, the reaction of Cu₂(OAc)₄·2H₂O with LH₃ in the presence of NEt₃ in MeOH under solvothermal conditions affords the complex [Cu^II₄(LH)₄] (<b>4</b>), while the same reaction under ambient temperature and pressure conditions forms [Cu^II₄(LH)₄] ·3.5MeOH·2.25H₂O (<b>5</b>·3.5MeOH·2.25H₂O). Complex <b>1</b> is a mixed-valent [Co^III₂Co^II₃] complex, consisting of three edge-sharing [Co₃] triangles. Complex <b>2</b> is a nickel­(II) monomer in which the central metal is found in an octahedral geometry, while complex <b>3</b> describes a [Ni^II₄] cubane. Complexes <b>4</b> and <b>5</b> may be considered as structural isomers because they possess the same formulas but different topologies: <b>4</b> describes a highly distorted [Cu^II₄(OR)₄]⁴⁺ eight-membered ring, while <b>5</b> consists of a distorted [Cu^II₄(μ₃-OR)₄]⁴⁺ cubane. In addition, <b>5</b> can be converted to <b>4</b> in excellent yield under solvothermal conditions. Direct-current magnetic susceptibility studies have been carried out in the 5–300 K range for complexes <b>1</b> and <b>3</b>–<b>5</b>, revealing the possibility of a high-spin ground state for <b>1</b>, an <i>S</i> = 4 ground state for <b>2</b>, and diamagnetic ground states for <b>4</b> and <b>5</b>