Solid-state UV-vis Absorption Research Articles

Development of pyrene-based MOFs probe for water content and investigations on their mechanochromism and acidochromism

A smart fluorescent pyrene-based MOFs (HPU-26) was synthesized by the solvothermal method, which possessed multi-stimuli-responsive properties and could detect water content in common organic solvents. The reversible multicolor fluorescent switching between yellowish green and cyan were observed under the stimulation of force, heating, and acid-base vapors. PXRD pattern, DSC curve, FI-IR spectra and the solid-state UV–vis absorption spectra were conducted to prove that the changes of π - conjugation induced the transformations between excimer and monomer formation under external stimulation, thus resulting in different fluorescent properties. In addition, HPU-26 could realize the detection of water content by remarkable change of fluorescent color from yellowish green to blue with increasing the water content in common organic solvents, which was attributed to the decomposition of crystal structure. The limit of detection (LOD) values of HPU-26 for detecting the water content in EtOH, DMA, Acetone and ACN were determined as 0.0260 %, 0.0578 %, 0.1978 %, and 0.5637 % (v/v), respectively. Furthermore, HPU-26 could be applied in advanced anti-counterfeiting and convenient visual detection of water content in common organic solvents by smartphone-based software.

Heterometallic Mo–Ti oxo clusters with metal–metal bonds: Preparation and visible-light absorption behaviors

In this work, two heterometallic clusters, namely Ti^IV₄Mo^V₄Mo^VI₂O₁₆(OCH₃)₁₆ (<strong>1</strong>) and Ti^IV₄Mo^V₄O₁₀(OC₂H₅)₁₄ (C₆H₅COO)₂ (<strong>2</strong>) are successfully constructed to improve the solar absorption and performance of titanium oxo clusters (TOCs). The <strong>1</strong> and <strong>2</strong> structures are determined well by single-crystal X-ray diffraction analysis and found to feature the common presence of Mo–Mo interactions. The solid-state UV–vis absorption studies indicate that these structures exhibit enhanced visible-light absorption and significantly reduced optical band gaps, which should be dominantly attributed to the introduction of electron-rich Mo–Mo pairs as heterometals. This work demonstrates an effective strategy of regulating the light absorption behaviors of TOCs by importing electron-rich heterometals.

Experimental and theoretical studies of photophysical properties of N-Substituted iminocoumarins

The photophysical properties of a set of new synthesized iminocoumarins and their N-substituted dyes have been investigated by means of experimental spectroscopy and DFT and TDDFT theoretical calculations. These materials act as push-pull systems consisting of free iminocoumarins and N-substituted by the dicyanovinyl function, that bearing different electron donor and acceptor groups. All the dyes were firstly characterized by NMR and IR experimental spectroscopy. Their photophysical properties are then examined by solid state UV–Vis absorption and fluorescence. Good agreement between experimental and theoretical UV–Vis absorption features was found. The main interests revealed are the substitution and coupling effects on the light absorption and emission characteristics. Attractive and motivating findings were spelled out such a bathochromic shift, gap energy lowering and Stokes shift enhancement. The N-substitution leaded to new red emitting dyes with good stabilities that could be very interesting in optoelectronic devices applications.

One-Pot Synthesis and Characterization of Three Chromotropic Supramolecular Isomeric Cu(II) Coordination Polymers as 1-D Zigzag or Helical Chains with Homochiral or Heterochiral Cu(II) Coordination Centres

The reaction of 1,10-phenanthroline (Phen) and 4′,4′''-(perfluoropropane-2,2-diyl) bis(([1,1′-biphenyl]-4-carboxylic acid)) (H2L2) with Cu(CH3COO)2⋅H2O in DMF/H2O at 50 ∼ 90°C in capped glass vials afforded three products with distinctively different colours and shapes. Single crystal X-ray diffraction analysis revealed that the three products, namely {[Cu(phen)(L2)] ⋅ 1.25H2O} (1) (teal acicula, KPI = 60.6%), {[Cu(phen)(L2)]⋅ H2O⋅DMF}n(2) (sapphire blue plate, KPI = 65.6%) and {[Cu(phen)(L2)]⋅0.31H2O}n (3) (cool grey plate, KPI = 66.8%) are 1-D supramolecular Cu(II) coordination polymers. Both 1 and 2 are composed of 1-D zigzag chains with 1 contains heterochiral Cu(II) (Λ- and Δ- alternatively) centres in the same chain and 2 contains homochiral Cu(II) (Λ- or Δ-) centres in the same chain, while 3, containing homochiral Cu(II) (Λ- or Δ-) centres, has a helical structure along a axis, with a rectangular channel of a size 19.61 × 16.61 Å2. Each helical turn spans 10.74 Å, composed of two [Cu(L2)(Phen)] units. With the largest KPI (∼66.3%), the highest thermal stability, highest formation energy from DFT calculations and lowest hygroscopicity, 3 can be obtained as the only product at higher temperature (95°C) and/or higher ratio of water (DMF/water (v/v) = 20:6), which implies that it is the thermodynamic product. 2 can be obtained at mediate temperature (60 ∼ 80°C) as the only product or co-exist with other products, while 1 only appeared at low temperature (60 and 70 °C) in the solvents of DMF/water (v/v) = 20:2 or 20:3 at a very small amount. The chromotropism of the three isomers was examined using UV-Vis spectroscopic technique, and the coordination geometry of Cu(II) was examined with Hathaway's tetragonality analysis and Continuous Shape Measures Calculation using SHAPE 2.1 programme. Linear correlations between the solid-state UV-Vis absorption maxima of the three isomers against the tetragonality (T) or the distortion percentage of the coordination geometry of Cu(II) from a perfect octahedral (Doct) were observed. The three complexes were also analyzed by FT IR, TGA and DFT formation energy calculations. The thermodynamic stability and the thermal stability of the three isomer increases in order of 1 < 2 < 3, supported by the analysis of the metal-ligand coordination bonds and the intermolecular interactions, the study of chromotropism and crystal fields, the effects of solvent polarity and temperature to the formation of isomers, the close-packing theory (KPI calculations), the DFT calculations and the TGA analysis.

A Smart Molecule Showing Spin Crossover Responsive Aggregation-Induced Emission

A Smart Molecule Showing Spin Crossover Responsive Aggregation-Induced Emission

Homochiral Mn3+ Spin-Crossover Complexes: A Structural and Spectroscopic Study.

Structural, magnetic, and spectroscopic data on a Mn3+ spin-crossover complex with Schiff base ligand 4-OMe-Sal2323, isolated in crystal lattices with five different counteranions, are reported. Complexes of [Mn(4-OMe-Sal2323)]X where X = ClO4– (1), BF4– (2), NO3– (3), Br– (4), and I– (5) crystallize isotypically in the chiral orthorhombic space group P21212 with a range of spin state preferences for the [Mn(4-OMe-Sal2323)]+ complex cation over the temperature range 5–300 K. Complexes 1 and 2 are high-spin, complex 4 undergoes a gradual and complete thermal spin crossover, while complexes 3 and 5 show stepped crossovers with different ratios of spin triplet and quintet forms in the intermediate temperature range. High-field electron paramagnetic resonance was used to measure the zero-field splitting parameters associated with the spin triplet and quintet states at temperatures below 10 K for complexes 4 and 2 with respective values: DS=1 = +23.38(1) cm–1, ES=1 = +2.79(1) cm–1, and DS=2 = +6.9(3) cm–1, with a distribution of E parameters for the S = 2 state. Solid-state circular dichroism (CD) spectra on high-spin complex 1 at room temperature reveal a 2:1 ratio of enantiomers in the chiral conglomerate, and solution CD measurements on the same sample in methanol show that it is stable toward racemization. Solid-state UV–vis absorption spectra on high-spin complex 1 and mixed S = 1/S = 2 sample 5 reveal different intensities at higher energies, in line with the different electronic composition. The statistical prevalence of homochiral crystallization of [Mn(4-OMe-Sal2323)]+ in five lattices with different achiral counterions suggests that the chirality may be directed by the 4-OMe-Sal2323 ligand.

A Multicenter Metal–Organic Framework for Quantitative Detection of Multicomponent Organic Mixtures

A Multicenter Metal–Organic Framework for Quantitative Detection of Multicomponent Organic Mixtures

Isomeric sp2-C-conjugated porous organic polymer-mediated photo- and sono-catalytic detoxification of sulfur mustard simulant under ambient conditions

Isomeric sp2-C-conjugated porous organic polymer-mediated photo- and sono-catalytic detoxification of sulfur mustard simulant under ambient conditions

A self-sensitized Co (II)-MOF for efficient visible-light-driven hydrogen evolution without additional cocatalysts

Herein, a new metal-organic framework (MOF) {[Co(azpy) (bps) (H2O)]·DMF·2.3H2O}n, 1, (azpy ​= ​4,4′-azopyridine, H2bps ​= ​4, 4′- bibenzoic acid-2, 2′-sulfone (H2bps) has been synthesized by solvothermal method. Complex 1 was characterized in detail by X-ray single-crystal diffraction, elemental analysis, IR spectrum, PXRD and thermogravimetric analysis. X-ray single-crystal diffraction analysis for 1 indicates that two azpy ligands bearing unusual cis-configuration bridge two Co2+ cations, forming an interesting one-dimensional nanopore channel. And these nanopore channels finally form a three-dimensional framework by multiple π···π stacking interactions. Besides, visible-light-driven H2 production exhibited that complex 1 displayed a high-efficiently photocatalytic hydrogen generation (1.44 ​mmol ​g−1·h−1) without additional photosensitizers and cocatalysts. Moreover, the photocurrent response of 1, solid-state UV–Vis absorption spectra of 1 and free ligands were also explored.

Stabilization of Plutonium(V) Within a Crown Ether Inclusion Complex

Crystalline coordination complexes of actinides, especially in atypical oxidation states, are not only fundamentally important for expanding the notably limited knowledge on the bonding nature of a...

Fenol-4-Sülfonik Asit ve 1,3-Bis(4-Piridil)Propan Tabanlı Yeni Organik Bileşiğin Hidrotermal Sentezi ve Karakterizasyonu

Bu çalışmada, yeni iki-boyutlu organik bileşik [PSA2][BPP2] (psa=fenol-4-sülfonik asit, bpp=1,3-Bis(4-piridil)propan) hidrotermal yöntem ile sentezlendi, tek kristal X-ışını kırınımı, toz kristal X-ışını kırınım yöntemi (PXRD), element analizi ve katı-hal UV-vis spektroskopisi ile karakterize edildi. Kristal yapı analizi, bileşiğin ortorombik kristal sisteminde Pca21 uzay grubunda kristalleştiğini ve asimetrik biriminde iki psa ve iki bpp ligandından oluştuğunu göstermektedir. Fenol ve piridil grupları neredeyse düzlemseldir. Ek olarak, bileşiğin kristal yapısı moleküller arası O–H…O, C–H…O hidrojen bağlarının yanı sıra molekül içi C–H…π ve bpp molekülleri arasında meydana gelen π - π etkileşimleriyle iki-boyutlu yapıyı oluşturmuş ve yapısal kararlılık sağlamıştır.

Structural characterization and photochromic behaviour of a novel compound based on a π-acidic naphthalene diimide derivative and a double hydroxide-bridged dinuclear AlIII aqua ion cluster.

Noncovalent interactions, such as π-π stacking interactions, C-H...π interactions and hydrogen bonding, are important driving forces for self-assembly in the construction of functional supermolecules and materials, especially in multicomponent supramolecular systems. Herein, a novel compound based on a π-acidic naphthalene diimide derivative and a double hydroxide-bridged dinuclear Al3+ aqua ion cluster, namely bis[N,N'-bis(2-sulfonatoethyl)-1,4,5,8-naphthalene diimide] di-μ-hydroxido-bis[tetraaquaaluminium(III)] tetrahydrate, (C18H12N2O10S2)2[Al2(OH)2(H2O)8]·4H2O, was obtained using the above-mentioned common noncovalent interactions, as well as uncommon lone-pair-π interactions. Functional molecular modules were connected by these noncovalent interactions to generate obvious photochromic properties. The compound was prepared by the self-assembly of N,N'-bis(2-sulfoethyl)-1,4,5,8-naphthalene diimide and Al(NO3)3·9H2O under mixed solvothermal conditions, and was characterized in detail by single-crystal X-ray diffraction, powder X-ray diffraction and FT-IR spectroscopy. The thermal stability and photochromic properties were also investigated; furthermore, in-situ solid-state UV-Vis absorption spectroscopy and electron spin resonance (ESR) were used to clarify the photochromic mechanism.

Multicolor Mechanochromism of a Polymer/Silica Composite with Dual Distinct Mechanophores.

The development of a multicolor mechanochromic polymer/silica composite is achieved by using two distinct types of mechanochromophores. The multicolor mechanochromism of the composite containing diarylbibenzofuranone in silica-rich domains and naphthopyran in the polymer-rich domain is observed. The obtained composite shows blue, green, and orange colors according to the intensity of applied mechanical stimuli, solvent addition, and lapse of time. This unique multicolor mechanochromic behavior is evaluated by solid-state UV-vis absorption spectroscopy, ab initio steered molecular dynamics simulations, and computed minimum energy paths on force-modified potential energy surfaces. The unique mechanochromism is attributed to the difference in properties, activated colors, and domain locations between the two mechanochromophores.

Synthesis, structural characterization and photoluminescent properties of 2D multilayer Cu+ coordination polymers via C[sbnd]H⋯π and π⋯π interactions

Two Cu(I) coordination polymers, {[Cu(pmbb)0.5(4,4'-bipy)0.5(PPh3)](BF4) (H2O)2}n (1) and {[Cu(pmbb)0.5(bpe)0.5(PPh3)](BF4)(DMF)}n (2) (pmbb = N, N'-bis(pyridin-2-ylmethylene)biphenyl −4,4'-diamine, 4,4'-bipy = 4,4'-bipyridine, bpe = 1,2-bis(4-pyridyl)ethylene), PPh3 = triphenyl phosphine), have been synthesized and characterized by IR, 1H NMR, 13C NMR, 31P NMR, 19F NMR, 11B-NMR, TG and X-ray crystal structure analysis. The structural analysis shows that complexes 1 and 2 contain diverse and interesting 2D supramolecular networks based on inter-chain interactions. Complex 1 displays a 1D zig-zag chain and a 1D+1D→2D supramolecular network formed by intermolecular CH···π interaction. For 2, each 1D zig-zag chain interacts with neighboring ones via intermolecular CH···π and π···π stacking interactions, leading to the formation of a 2D-stacking network. Furthermore, solid-state UV–Vis absorption spectra of complexes 1 and 2 indicate the existence of MLCT absorption. Complexes 1 and 2 show efficient luminescent emission peaks at 435 and 452 nm assigned to MLCT excited states, and the emission decay lifetimes are 20.82 μs for 1 and 20.72 μs for 2, displaying strong room-temperature solid-state photoluminescence. Moreover, thermogravimetric analysis shows that the heat stability of polymers is 1>2.

Diverse binding of important anions in 1-D tricopper anion coordination polymer (ACP) architectures

With the idea of supramolecular hosts encircling monoanions, a series of urea-containing trinuclear cationic copper complexes were designed, prepared and structurally analyzed. Copper(I) acetylides [Cu3(μ-dppm)3(μ3-η1-CCC6H4-4-NHC(O)NHC6H4-4-R)2]+ (dppm = bis(diphenylphosphino)methane; R = NO2 (1), CF3 (2), Cl (3), H (4), tBu (5), and OCH3 (6)) were prepared with F−, BF4−, or NO3− present as the anion. Eight 1-D anion coordination polymers (ACPs), 1·F, 2·F, 3·BF4, 4·F, 5·F, 5·BF4, 5·NO3 and 6·0.5F·0.5BF4, were clearly determined by X-ray diffraction. Diversity in the polymeric architecture is generated by both the choice of R-group used and anion present. 2·F, 3·BF4, 4·F, and 5·F show linear 1-D structures; 5·BF4 and 5·NO3 feature single-stranded helical structures; 1·F and 6·0.5F·0.5BF4 exhibit meso-helical structures. Solid state UV-vis absorption and luminescence properties are also discussed.

Three isostructural coordination polymers and highly selective fluorescent probe for Ag+ in aqueous media

Three isostructural compounds [M(DPFE)(bpda)(H2O)2]n [M=Co(1), Mn(2), Cd(3)] have been synthesized hydrothermally and structurally characterized, where DPFE=2,7-di(pyridin-4-yl)-9H-fluorene and H2bpda=biphenyl-3,4′-dicarboxylic acid. Compounds 1–3 show a unique 2D structure where exists two sets of chains toward two different directions. The solid-state UV–vis absorption spectra of 1–2 and the fluorescence spectrum of 3 are discussed in detail. In addition, compound 3 exhibits relatively high selective ability to detect Ag+ ion in aqueous media.

Synthesis, structural characterization and photoluminescent properties of copper(I) coordination polymers with extended C–H⋯π and CN⋯π interactions

Two copper(I) coordination polymers, {[Cu2(pmb)(4,4′-bipyridine)(PPh3)2] (BF4)2(CH3CN)2}n (1) and {[Cu2(pmb)(bpe)(PPh3)2](BF4)2(CH3CN)(H2O)}n (2) (pmb=N,N′-bis(pyridin-2-ylmethylene)benzene-1,4-diamine, bpe=1,2-bis(4-pyridyl)ethylene), PPh3=triphenylphosphine), have been prepared and characterized by IR, 1H NMR, 13C NMR, 31P NMR, 19F NMR, 11B NMR, TG and X-ray crystal structure analysis. The structural analysis shows that each 1D zig-zag chain in 1 interacts with neighbouring acetonitrile molecules, interestingly, which results in the formation of CN⋯π interactions around this chain. For 2, 1D helical tube is formed by directly linking horse-shoe shaped collar with a 32-membered split ring, while C–H⋯π interaction results in the stacking of 1D helical tube into a 3D network. In complexes 1 and 2, the solid-state UV–Vis absorption peaks show the existence of MLCT absorption. Furthermore, complexes 1 and 2 indicate efficient luminescent emission peaks near 450nm attributed to MLCT excited states, and the emission decay lifetimes of complexes 1 and 2 are 28.33μs and 29.99μs, showing strong solid-state photoluminescence at room temperature. In addition, TG-DTA reveals that the heat stability of these complexes is 1>2.

Visible light photocatalytic activity of novel Ni2+, Cu2+ and VO2 complexes derived from vanillin bidentate Schiff base ligand doped on TiO2 nanoparticles

A new bidentate NN-Schiff base ligand of vanillin, (E)-4-(((2-amino-5-nitrophenyl)imino)methyl)-2-methoxyphenol, was synthesized and characterized by different spectroscopic techniques. In addition, mononuclear complexes were synthesized by treating the corresponding metal salts of Ni2+, Cu2+ and VO2 and Schiff base ligand in methanol. The resulting complexes were characterized by FT-IR, UV–Vis and 1H NMR techniques. The hybrids of complex/TiO2 nanoparticles were prepared and their structure and morphology were characterized by FT-IR, XRD, TEM, SEM and solid state UV–Vis absorption. Furthermore, Kubelka–Munk transformations were used to measure the absorption curves and band gap. The photocatalytic activities of the prepared modified semiconductors were tested under visible radiation for the degradation of methylene blue in the aqueous solution. The results indicated that the incorporation of these complexes improved the activation of TiO2 with visible light.

Two isostructural cobalt(II) coordination polymers with both polyrotaxane and polycatenane features assembled with a V-shaped rigid ligand

Two novel cobalt(II) coordination polymers (CPs), [Co(BPFP)2(sca)]n (1), [Co(BPFP)2(sda)]n (2), [BPFP=2,8-di(pyridin-4-yl)dibenzo[b,d]furan, H2sca=succinic acid, H2sda=thiophene-2,5-dicarboxylic acid], have been synthesized hydrothermally based on a V-shaped rigid ligand BPFP. Their structures were fully characterized by elemental analysis, FT-IR spectroscopy and X-ray single-crystal diffraction methods. Compound 1 is a 2-fold parallel interpenetrating network consist of two identical sets of 2D layer motifs and shows both polyrotaxane and polycatenane characters. Compound 2 has the same structural feature as compound 1, except that the sca2− anions are replaced by the sda2− anions. The Powder X-ray diffraction (PXRD) analyses and thermogravimetric analyses were carried out to confirm the phase purity and the thermal stabilities of the compounds 1 and 2. In addition, the solid-state UV–vis absorption spectra were also investigated.

When long bis(pyrazolates) meet late transition metals: structure, stability and adsorption of metal–organic frameworks featuring large parallel channels

A family of bis(pyrazolato)-based metal-organic frameworks (MOFs) was isolated by reacting 1,4-bis(1H-pyrazol-4-ylethynyl)benzene (H2BPEB) with a number of transition metal ions. Special attention was dedicated to their structural features, their thermal and chemical stability, as well as their spectroscopic and adsorption properties. The rod-like ligands, connecting Zn(II), Ni(II) and Fe(III) nodes, fabricate 3-D networks containing 1-D pervious channels. The combination of thermal analysis and variable-temperature XRPD demonstrated the remarkable thermal robustness of the three materials, which are stable in air up to at least 410 °C, and showed their structural response to increasing temperature. Specific experiments permitted us to test the chemical stability of the three species toward water as well as moderately acidic and basic solutions, the Ni(II) derivative being stable and hydrophobic in all the conditions assayed. The electronic transitions of both the ligand and the MOFs were investigated by solid-state UV-Vis absorption as well as by steady-state and time-resolved fluorescence analysis, which showed that the high fluorescence of the linker is perturbed in the three MOFs, suggesting high sensitivity to environmental changes. N2 adsorption measurements at 77 K allowed to estimate promising Langmuir specific surface areas, peaking at 2378 m2 g−1 in the case of the Ni(II) derivative. The best CO2 and CH4 uptake performances were achieved with the Fe(III)-based MOF. Indeed, adsorption experiments with CO2 revealed that a considerable amount, up to 40% wt, is adsorbed by the Fe(III) derivative under the mild conditions of 298 K and 10 bar.