Two‑Dimensional Copper Coordination Polymer Assembled with Fumarate and 5,5’‑Dimethyl‑2,2’‑bipyridine: Synthesis, Crystal Structure and Magnetic Properties

[[Cu(fum)(dmb)]·H2O]n, exhibiting weak antiferromagnetic interactions, displays a two-dimensional array comprised of rhombic dinuclear units, where the carboxylate moieties of fumarate bridging ligand displays monodentate and oxo-bridging coordination modes connecting two Cu centers.[[Cu(fum)(dmb)]·H2O]n (1) (fum = fumarate; dmb = 5,5’-dimethyl-2,2’-bipyridine) was obtained by a self-assembly solution reaction, at ambient conditions, and characterized by elemental analysis, IR spectroscopy and X-ray single crystal diffraction. Crystallographic studies show that 1 crystallizes in a triclinic system with a P-1 space group, with a = 8.2308(2) Å, b = 9.7563(2) Å, c = 10.3990(2) Å; α = 80.3444(4)°, β = 77.9517(4)°, γ = 82.0440(5)°; V = 800.45(3) Å3. The Cu(II) centers are five-coordinated with a distorted square pyramidal configuration. The formation of a two-dimensional (2D) array in 1 can be explained by the presence of two different coordination modes in the fumarate ligand: μ-η1:η0 and μ2-η2:η0, both in a bridging monodentate manner, the latter generating distinctive rhombic-dinuclear units. The thermal stability of 1 has also been analyzed. Magnetic measurements revealed that this polymer exhibits weak antiferromagnetic ordering.Universidad Autonoma del Estado de México Universidad Nacional Autónoma de Méxic

Drastic Effect of Lattice Propionitrile Molecules on the Spin-Transition Temperature of a 2,2\u2032-Dipyridylamino/s-triazine-Based Iron(II) Complex

Reaction of iron(II) selenocyanate (obtained from Fe(ClO4)2 and KNCSe) with 2-(N,N-bis(2-pyridyl)amino)-4,6-bis(pentafluorophenoxy)-(1,3,5)triazine (L1F) in propionitrile produces the compound [Fe(L1F)2(NCSe)2].2CH3CH2CN (1NCSe.2PrCN), which shows spin-crossover (SCO) properties characterized by a T1/2 of 283 K and a ?T80 (i.e., temperature range within which 80% of the transition considered occurs) of about 65 K. Upon air exposure, 1NCSe.2PrCN gradually converts to a new SCO species that exhibits different properties, as reflected by T1/2 = 220 K and ?T80 = 70 K. Various characterization techniques, namely, IR spectroscopy, thermogravimetric analysis, and thermodiffractometric studies, reveal that the new phase is obtained through the loss of the lattice propionitrile molecules within several days upon air exposure or several hours upon heating above 390 K

Human sensor-inspired supervised machine learning of smartphone-based paper microfluidic analysis for bacterial species classification

Bacteria identification has predominantly been conducted using specific bioreceptors such as antibodies or nucleic acid sequences. This approach may be inappropriate for environmental monitoring when the user does not know the target bacterial species and for screening complex water samples with many unknown bacterial species. In this work, we investigate the supervised machine learning of the bacteria-particle aggregation pattern induced by the peptide sets identified from the biofilm-bacteria interface. Each peptide is covalently conjugated to polystyrene particles and loaded together with bacterial suspensions onto paper microfluidic chips. Each peptide interacts with bacterial species to a different extent, leading to varying sizes of particle aggregation. This aggregation changes the surface tension and viscosity of the liquid flowing through the paper pores, altering the flow velocity at different extents. A smartphone camera captures this flow velocity without being affected by ambient and environmental conditions, towards a low-cost, rapid, and field-ready assay. A collection of such flow velocity data generates a unique fingerprinting profile for each bacterial species. Support vector machine is utilized to classify the species. At optimized conditions, the training model can predict the species at 93.3% accuracy out of five bacteria: Escherichia coli, Staphylococcus aureus, Salmonella Typhimurium, Enterococcus faecium, and Pseudomonas aeruginosa. Flow rates are monitored for less than 6 s and the sample-to-answer assay time is less than 10 min. The demonstrated method can open a new way of analyzing complex biological and environmental samples in a biomimetic manner with machine learning classification.11Nsciescopu

A Series of Cyanoacetato Copper(II) Coordination Polymers with Various <i>N</i>,<i>N</i>′‑Ditopic Spacers: Structural Diversity, Supramolecular Robustness, and Magnetic Properties

Five novel copper­(II) coordination polymers containing cyanoacetate (cna) anion with various <i>N</i>,<i>N</i>′-ditopic spacers [Cu­(cna)₂­(pyz)]_<i>n</i> (<b>1</b>), [Cu­(cna)₂­(bpy)­(H₂O)₂]_<i>n</i> (<b>2</b>), [Cu­(cna)₂­(dpe)]_<i>n</i> (<b>3</b>), [Cu­(cna)₂­(dpe)]_<i>n</i>­(H₂O)_<i>n</i> (<b>4</b>), and [Cu­(cna)₂­(bpa)]_<i>n</i> (<b>5</b>) (when pyz = pyrazine, bpy = 4,4′-bipyridyl, dpe = 1,2-di­(4-pyridyl)­ethylene, and bpa = 1,2-di­(4-pyridyl)­ethane) were structurally and spectroscopically characterized. Compound <b>1</b> shows a two-dimensional (2D) sheet structure constructed from μ₂-1,3­(<i>syn,anti</i>) coordinative mode of cyanoacetate and μ₂-pyz linking adjacent Cu­(II) centers. Compound <b>2</b> exhibits a one-dimensional (1D) polymeric chain which is formed by μ₂-bpy bridging between [Cu­(cna)₂­(H₂O)₂] units, whereas compounds <b>3</b>–<b>5</b> reveal 1D ladder-like structures which are built from double-μ₂-dpe/bpa spacers connecting neighboring Cu­(II) cyanoacetate dimers. Weak interactions such as hydrogen bonding and N<i>···π</i> and/or C–H<i>···π</i> interactions join the adjacent layers of <b>1</b> or polymeric chains of <b>2</b>–<b>5</b> to stabilize overall supramolecular networks. The thermal stabilities of <b>1</b>–<b>5</b> were investigated. Interestingly, compound <b>2</b> reveals a robust supramolecular framework constructed by 1D polymeric chains during thermal dehydration and rehydration processes, which has been further verified by spectroscopic techniques, elemental analyses, thermogravimetric analysis, and X-ray powder diffraction. Moreover, this behavior is not observed in the isomorphous series containing Co­(II) and Ni­(II) ions. The magnetic properties of <b>1</b> and <b>3</b> exhibit very weak antiferromagnetic interactions between Cu­(II) centers