Study of implementation of the Flipped Classroom methodology (Just In Time Teaching) in the Inorganic Materials elective course of the Chemistry Degree at University of Barcelona

The Flipped Classroom (FC) strategy was implemented in an elective course of the Chemistry Degree at UB under its Just In Time Teaching approach. The methodology includes a self-studying activity, an assessment of students' initial level, the on-site FC session, and a verification of their achievements. The results evidenced some deficiencies in the assessment of student's achievements. Nevertheless, students highly appreciated the methodology, which helped them to develop self-learning skills

Tm(III) complexes undergoing slow relaxation of magnetization: exchange coupling and aging effects

The present study focuses on the dynamical magnetic behaviour of exchange coupled 3d-4f complexes containing the scarcely considered non Kramers Tm3+ center, the 3d metal ions being either the low-spin Fe3+ (1) or the diamagnetic Co3+ (2) ion. Both complexes display field-dependent slow relaxation of magnetization. The field and temperature dependences of the relaxation rate provided indication of relevant contributions from quantum tunnelling, direct and Raman processes, with only minor effects from exchange coupling interactions. Furthermore, aged sample of 2 exhibited additional relaxation process, possibly due to solvent loss, highlighting the importance of a careful consideration of this factor when analysing the magnetization dynamics in solvated systems

Trinuclear heterometallic CuII-MnII complexes of a salen type Schiff base ligand: anion dependent variation of phenoxido bridging angles and magnetic coupling

Five new trinuclear heterometallic CuII-MnII complexes [(CuL)2Mn(O2CPh)2] (1), [(CuL)2Mn(N3)2] (2), [(CuL)2Mn(NCO)2] (3), [(CuL)2Mn(NO3)2] (4) and [(CuL)2Mn(Sal)2]∙CH2Cl2 (5) have been synthesized with the di-Schiff base ligand H2L (where, H2L= N,N'-bis(salicylidene)-1,3-propanediamine and Sal= salicylate). These complexes with different anionic co-ligands have been synthesized to attain a large variation in phenoxido bridging angles and to investigate its consequence on magnetic properties. Single crystal X-ray diffraction analyses reveal that complexes 1, 2, 4 and 5 are linear, whereas 3 has an angular geometry. Variable temperature magnetic susceptibility measurements suggest that all five complexes possess an overall antiferromagnetic interaction between CuII and MnII ions, which results in a final ferrimagnetic ground state with spin 3/2 in the CuII-MnII-CuII trinuclear structure. The weakest antiferromagnetic interaction (JCu-Mn= -7.0 cm-1) is observed for 2 having the lowest value of the Cu-O-Mn angle (92.0°), while the strongest antiferromagnetic interaction (JCu-Mn= -26.5 cm-1) is observed for 3 having the largest Cu-O-Mn angle (101.4°). Complexes 1, 4 and 5 show an average Cu-O-Mn angles of 98.2°, 97.6° and 97.7°, respectively, that lead to intermediate antiferromagnetic interactions (JCu-Mn = -9.6, -9.7, -9.3 cm-1 respectively)

Double mu(2)-(phenoxido)-bridged dinuclear and polynuclear nickel(II) complexes: magnetic properties and DNA/protein interaction

One dinuclear and one 1D polymeric nickel(II) complex, namely {[Ni2(HL)2(pa)2(H2O)2]·DMF} (1) and {[Ni2(HL)2(ppda)(H2O)2]·DMF·H2O}n (2) (H2L = (E)-2-((1-hydroxybutan-2-ylimino)methyl)phenol, pa = 3-phenylacrylate, ppda = p-phenylenediacrylate) have been synthesized and characterized by X-ray single crystal structure determination. Complex 1 is double phenoxo-bridged dinuclear Ni(II) complex, whereas complex 2 is a 1D polynuclear chain where double phenoxo-bridged dinuclear units are connected through bridging ppda ligands. The variable temperature magnetic behavior of the complexes was studied using the Hamiltonian H = −JS1S2, S1 = S2 = SNi and confirms the presence of an overall antiferromagnetic interaction in both complexes. Good agreement between the experimental and simulated curves were found using the parameters: gNi = 2.15, DNi = 4.0 cm−1 and JNi-Ni = −0.60 cm−1 for 1, and gNi = 2.15, DNi = 4.8 cm−1 and JNi-Ni = −3 cm−1 for 2. The interactions of the complexes with CT-DNA were investigated using UV-Vis absorption and fluorescence spectroscopic methods and they show that both the complexes interact with CT-DNA. The intrinsic binding constants values for interaction with CT-DNA are 3.9(±0.10) × 105 and 3.43(±0.09) × 105 M−1 for 1 and 2, respectively. The interactions of the complexes with bovine serum albumins (BSA) and human serum albumins (HSA) were also studied using electronic absorption and fluorescence spectroscopic techniques and the results show that both complexes interact with the serum albumins via a ground state association process

Structural and magnetic characterization of three tetranuclear Cu(II) complexes with face-sharing-dicubane/double-open-cubane like core framework

Three novel tetranuclear copper(II) complexes namely [Cu4(L1)4]∙(dmf) (1), [Cu4(L1)4] (2) and [Cu4(L2)2(HL2)2(H2O)2]∙2(ClO4)∙6(H2O) (3) (H2L1, (E)-2-((1-hydroxybutan-2-ylimino)methyl)phenol; H2L2, (E)-2-((1-hydroxybutan-2-ylimino)methyl)-6-methoxyphenol)) were synthesised from the self-assembly of copper(II) perchlorate and the tridentate Schiff base ligands. The structural determination reveals that complex 1 crystallizes in the monoclinic system with space group C2/c, whereas both the complexes 2 and 3 crystallize in the triclinic system with space group P-1. Complexes 1 and 2 possess face-sharing dicubane core, on the other hand complex 3 has double open cubane core structure. The copper(II) ions in the cubane core are in distorted square planar geometries, and weak π¿π and C-H¿π interactions lead to formation of a 2D supramolecular architecture for complexes 1 and 2. At room temperature complexes 1, 2 and 3, exhibit fluorescence with a quantum yield (Φs) of 0.47, 0.49 and 0.38, respectively. Variable temperature magnetic susceptibility measurements in the range 2-300 K indicate an overall weak antiferromagnetic exchange coupling in all complexes. The PHI program was used to study their magnetic behaviour. In agreement with their face-sharing dicubane structure, a Hamiltonian of the type H = - J1(S1S2+S1S2'+S1'S2+S1'S2') - J2S1S1', where S1 = S1' = S2 = S2' = SCu = 1/2, was used for studying complexes 1 and 2. Simulations performed suggest magnetic exchange constants with values close to J1 = -20 cm-1 and J2 = 0 cm-1 for these complexes. On the other hand, the spin Hamiltonian H = - J1(S1S4+S2S3) - J2(S1S3+S2S4) - J3S1S2, where S1 = S2 = S3 = S4 = SCu = 1/2, was used to study the magnetic behaviour of the double open cubane core of complex 3 and a good agreement between the experimental and simulated results was found by using the parameters g1 = g2 = 2.20, g3 = g4 = 2.18, J1 = -36 cm-1, J2 = -44 cm-1 and J3 = 0 cm-1

DNA/protein binding and magnetic properties of a 1D Cu(II) complex containing fumarate and tridentate Schiff base ligands

ID copper(II) complex, [Cu2(L)2(fum)]∙H2O}n (1) has been synthesized using fumarate (fum2-) and a Schiff base (HL), derived from the condensation reaction of 2-amino-1-butanol and salicyldehyde. Complex 1 has been characterized by X-ray crystal structure, FT-IR, electronic absorption and fluorescence spectroscopic methods. The structural determination reveals that complex 1 crystallizes in the monoclinic system with space group P21/n and form 1D polymeric chain, built by bridging fum. Weak π¿π and C-H¿π interactions in 1, lead to a 3D supramolecular architecture. Complex 1 exhibits fluorescence at room temperature with a quantum yield (Φs) of 0.257. The interactions of complex 1 with bovine serum albumin (BSA) and human serum albumin (HSA) were studied using electronic absorption and fluorescence spectroscopic techniques and the analysis shows that complex 1 interaction with BSA / HSA occurs mainly with ground state association process. Calculated values of apparent association constants are 1.34 × 104 M-1 and 1.81 × 104 M-1 for BSA and HAS, respectively, at 300 K. The number of binding sites and binding constants were calculated using double logarithm regression equation. The interaction of complex 1 with the calf thymus DNA (CT-DNA) was also investigated using electronic absorption and fluorescence spectroscopic methods. The results show that complex 1 has binding affinity to CT-DNA in the order of 2.96×105 M-1. Low temperature magnetic measurements reveal existence of antiferromagnetic interaction in complex 1. The magnetic data have been fitted considering complex 1 as a pseudo-dinuclear system, with the two copper(II) atoms bridged by two carboxylate oxygen atoms, since the coupling through long fum bridge is almost nil. The best-fit parameters obtained with this model are J = - 60 cm-1, gCu = 2.20

Two new μ2-(1,1-azido) and μ2-(1,1-phenoxido)-bridged dinuclear nickel(II) complexes: Syntheses, single-crystal structures and magnetic studies

Two dinuclear azido bridged Ni(II) complexes [Ni2(HL1)2(N3)(C8H7O3)]∙(H2O) (1) and [Ni2(L2)2(N3)2(H2O)](2) [H2L1 and HL2 are Schiff bases, obtained from the condensation of 2-hydroxy-3-methoxy-benzaldehyde with 2-amino-2-methyl-1-propanol and N,N-diethylethylene diammine, respectively; C8H7O3 = 3-methoxy-2-oxo-benzaldehyde] have been synthesized and their crystal structures have been determined. Complex 1, C32H39N5Ni2O10, crystallizes in a triclinic system, space group P-1 with a = 10.0846(6), b = 12.5179(7), c = 14.1176(8) Å, α = 74.3873(7), β =83.9553(7), γ = 83.1921(7) º and Z = 2; complex 2, C28H44N10Ni2O5 , crystallizes in an orthorhombic system, space group Pbca with a = 12.4197(1), b = 21.4737(4), c = 24.4569(5) Å, and Z = 8. X-ray single crystal structure determination reveals that both the complexes are dinuclear with μ2-(1,1-azido) and μ2-(penoxido) bridges. Variable temperature magnetic studies indicate overall ferromagnetic interaction between nickel(II) centers in both the complexes. The experimental magnetic data of the complexes were fitted using PHI program and isotropic Hamiltonian H = -JS1S2, where S1 = S2 = SNi. A zero-field splitting parameter (D) and intermolecular interaction term (zJ') were also considered in the model and a good agreement between experimental and simulated curves were found by using the following parameters: gNi= 2.13, DNi= 5.83 cm-1, JNi-Ni = 14.61 cm-1 and zJ' = -0.1 cm-1 for 1, and gNi= 2.15, DNi= 2.33 cm-1, JNi-Ni = 13.09 cm-1and zJ' = -0.07 cm-1 for 2

Ferro- to antiferromagnetic crossover angle in diphenoxido- and carboxylato-bridged trinuclear Ni(II)2-Mn(II) complexes: experimental observations and theoretical rationalization

Three new trinuclear heterometallic NiII-MnII complexes have been synthesized using [NiL] metalloligand where H2L = N,N′- bis(salicylidene)-1,3-propanediamine. The complexes [(NiL)4Mn2(OCn)4(CH3OH)4]·2CH3OH (1), [(NiL)4Mn2(OPh)4(CH3OH)2]·H2O (2) and [(NiL)4Mn(OSal)2(CH3OH)2] (3) (where OCn = cinnamate, OPh = phenylacetate, OSal= salicylate) have been structurally characterized. In all three complexes, in addition to the double phenoxido bridge, the two terminal NiII atoms are linked to the central MnII by means of syn-syn bridging carboxylate, giving rise to a linear structure. Complexes 1 and 2 with Ni-O-Mn angle of 97.24 and 96.43° respectively exhibit ferromagnetic interactions ( JNi-Mn = +1.38 and +0.50 cm-1 respectively) whereas 3 is antiferromagnetic (JNi-Mn= -0.24 cm-1) having Ni-O-Mn angle of 98.51°. DFT calculations indicate that there is a clear magneto-structural correlation between Ni-O-Mn angle and JNi-Mn values which is in agreement with the experimental results

Highly water-stable rare ternary Ag-Au-Se nanocomposites as long blood term X-rays computed tomography contrast agents

X-ray computed tomography (CT) is a powerful and widely used medical non-invasive technique that requires intravenously administration of contrast agents to enhance the sensitivity and visualization of soft tissues. In this work, we have developed a novel CT contrast agent based on ternary Ag-Au-Se chalcogenide nanoparticles. A facile and gentle ligand exchange by using a 3 kDa PEGylated ligand with a dithiol dihydrolipoic as an anchor resulted in highly water-soluble and monodisperse nanoparticles. Moreover, the injected PEGylated ternary NPs presented excellent characteristics as a CT contrast agent with high bioavailability, low cytotoxicity and long blood circulation times with slow uptake by the mononuclear phagocyte system, thus being ideal for in vivo imaging

Syntheses, crystal structures, and magnetic properties of metal-organic hybrid materials of Mn(II)/Co(II): three-fold interpenetrated alpha-polonium-like network in one of them

Three new 1,4-phenylenediacrylate bridged Mn(II) and Co(II) complexes with the molecular formulae {[Mn2(phen)4(H2O)2(ppda)]∙(ppda)∙2(H2O)}(1), {[Co(ppda)(dpyo)(H2O)3]∙4(H2O)}n (2), and {[Co(ppda)(bpe)]∙(0.5H2O)}n (3) [phen = 1,10-phenanthroline; ppda = 1,4-phenylenediacrylate; dpyo = 4,4´-dipyridyl N,N´-dioxide; bpe = 1,2-bis(4-pyridyl)ethane] have been synthesized and characterized by elemental analysis, IR spectra, single-crystal X-ray diffraction studies and low temperature magnetic measurements. Structural determination reveals that complex 1 is dinuclear, 2 is a 1D polymeric chain, while 3 is a three-fold interpenetrated α-polonium-like network. Hydrogen bonding interactions, formed by coordinated and/or lattice water molecules with ppda oxygen, and staking interactions of aromatic rings lead to a 3D supramolecular architecture in both complexes 1 and 2. Low temperature magnetic study shows antiferromagnetic coupling in all the complexes. In addition, their electronic and fluorescent spectral properties have also been investigated