pH-Independent Selective Formation of VO2+ Motif Incorporating a Family of Hydrazone Ligands: Synthesis, Structure, and Luminescence-Based Sensing Studies toward Selective Metal Ions

Two new dioxidovanadium(V) compounds with the general formula [VVO2(L)] (L = hydrazone ligand) were synthesized using three different methods (acidic, neutral, and basic media) with either VIVOSO4. 5H2O, [VIVO(acac)2], or NH4VVO3 as the starting material and hydrazone ligands. In both cases, five coordinated V5+ ions adopted distorted square pyramidal geometry through the coordination of two oxido ligands and one hydrazone ligand. In compound 1, the presence of free hydroxyl groups stabilized the molecular species through intramolecular O-H•••N type hydrogen bond interactions. In compound 2, the free amino groups are involved in both intramolecular N-H•••N type and intermolecular N-H•••O type hydrogen bond interactions. Compound 1 showed highly selective luminescence turn-on behavior, along with a 33-nm blue shift in the presence of Al3+ ions in an aqueous medium. The experimental limit of detection (LOD) was found to be 66 nM. Whereas compound 2 showed luminescence quenching behavior in the presence of Fe3+, Al3+, and Cr3+ ions. The LODs were observed to be 312, 408, and 280 nM for Fe3+, Al3+, and Cr3+ ions, respectively. The luminescence response mechanisms of both compounds in the presence of metal ions have been correlated with molecular-level interactions.

Clustering-triggered emission mechanism of carboxymethyl β-cyclodextrin aqueous solution and efficient recognition of Fe3+ in mixed ions

Most nonconventional luminogens enjoy good water solubility and biocompatibility, showing unique application prospects in fields like biological imaging. Although clustering-triggered emission (CTE) mechanisms have been proposed to explain such emissions, the have not been thoroughly elucidated, which limits their development and application. Here, the photoluminescence properties of carboxymethyl β-cyclodextrin (CM-β-CD) aqueous solution are utilized to further investigate the effects of changes in concentration, in order to elucidate the emission mechanism through cryo-transmission electron microscopy (cryo-TEM), small-angle X-ray scattering (SAXS), molecular interaction analysis, and theoretical calculation. The results showed that the size distribution, morphology, and distance between water aggregates were successfully correlated with the cluster emission centers. The emission mechanism of nonconventional luminogen solutions was more clearly and intuitively elucidated, which has a promoting effect on the emission and application of this field. It is interesting that temperature-dependent emission spectra show the blue-shift phenomenon of PL with increasing excitation wavelengths. Moreover, due to its strong static quenching effect for Fe3+, CM-β-CD can efficiently detect Fe3+ in mixed-ion aqueous solutions. It provides a strategy to clarify the CTE mechanism of nonconventional luminogen solutions more clearly and its application of mixed-ion detection.

Recent advances in the development of green furan ring-containing polymeric materials based on renewable plant biomass

Fossil resources are rapidly depleting, forcing researchers in various fields of chemistry and materials science to switch to the use of renewable sources and the development of corresponding technologies. In this regard, the field of sustainable materials science is experiencing an extraordinary surge of interest in recent times due to the significant advances made in the development of new polymers with desired and controllable properties. This review summarizes important scientific reports in recent times dedicated to the synthesis, construction and computational studies of novel sustainable polymeric materials containing unchanged (pseudo)aromatic furan cores in their structure. Linear polymers for thermoplastics, branched polymers for thermosets and other crosslinked materials are emerging materials to highlight. Various polymer blends and composites based on sustainable polyfurans are also considered as pathways to achieve high-value-added products.

Selective Luminescence Turn-On-Based Sensing of Phosphate in the Presence of Other Interfering Anions Using a Heterobimetallic (3d-4d) MOF with an Acidic Pocket

A luminescent metal-organic framework with the molecular formula [YMn_1.5(C₇N₁H₃O₅)₃(H₂O)₆]·11H₂O, 1 {where C₇N₁H₃O₅ = chelidamate}, was synthesized by a hydrothermal method by employing chelidamic acid as an organic ligand and Y(III) and Mn(II) as metal ions. A two-dimensional heterobimetallic structure with phenolic hydroxyl-functionalized pockets was revealed by single-crystal X-ray diffraction analysis of compound 1. PXRD, TGA, IR, BET analysis, and UV-vis spectroscopy were used for the thorough characterization of compound 1. Upon excitation at 280 nm, compound 1 shows bright blue emission, which was utilized for the selective and sensitive turn-on detection of the PO₄^3- ion. Based on Bronsted-Lowry acid-base interactions, the photoluminescence of compound 1 was enhanced in the presence of very low concentrations of the aforementioned anion. The mechanism behind the detection of the phosphate ion has been explored in detail. It was seen that the PO₄^3- anion entered the hydroxyl-functionalized pockets of compound 1 and stabilized the aromatic portion of compound 1 via molecular-level interactions through acid-base interactions. These molecular-level interactions are responsible for the enhancement of the photoluminescence intensity of compound 1 after the incorporation of phosphate ions by reducing the nonradiative transitions. These phenomena were also confirmed by time-correlated single photon counting (TCSPC) measurement, which shows that the excited-state lifetime increased with the increase in addition of phosphate anions. The calculated limit of detection (LOD) of 1 was 19.55 ppb for phosphate (PO₄^3-), which was significantly lesser than the recommended level for the PO₄^3-anion toward the human body. The luminescence enhancement coefficient, K_SV, value was also much higher than those of other reported metal-organic frameworks.

Fresh hetero-metallic compound as luminescent sensor for detection of CS2 and inhibitory activity on children diabetes

The combination of the dicarboxylate ligand of 2-aminoterephthalic acid (H₂L), Cd(NO₃)₂·4H₂O, and KNO₃ under hydrothermal condition formed a fresh hetero-metallic coordination polymer, namely, [CdK₂(L)₂(H₂O)₄]_n (1). The compound exhibited a high luminescence intensity at normal environment as well as high sensitivity and selectivity in the measurement of CS₂. The effect of the fresh compound on childhood diabetes was investigated. A blood glucose monitor was utilized to assess the blood glucose level of the body after the addition of the compound. Moreover, the relative expression level of the insulin recipient on hepatocytes was assessed by real time RT-PCR.

Stabilization of CO2 as Zwitterionic Carbamate within a Coordination Polymer (CP): Synthesis, Structure and Anions Sensing Behaviour of Tb-CP composite

A new gadolinium (III) based coordination polymer (CP), [Gd(3,5-pydc)1.5(CO2)0.5(H2O)4].3H2O (where 3,5-pydc =3,5-pyridinedicarboxylate) , 1, has been successfully synthesized using slow diffusion method at room temperature. Single crystal X-ray diffraction study...

A 2-fold interpenetrated zinc–organic framework with Lewis basic triazole sites: luminescence sensing of Fe3+ and Cr2O72−, and warm white-light emission by encapsulated Ln3+ ions

A 2-fold interpenetrated Zn-MOF with Lewis basic triazole sites shows selective luminescence sensing of Fe3+ and Cr2O72− and tunable white-light emission by encapsulated Ln3+ ions.

Coordination networks for the recognition of oxo-anions

Crystalline coordination networks with an infinite extended framework, also known as coordination polymers (CPs) or metal-organic frameworks (MOFs), have attracted significant attention owing to their tremendous performance in an extensive range of applications. The unique structural features and high stability of coordination networks are responsible for their utilization and potential in diverse fields especially in the area of sensing using luminescent CPs/MOFs. The recognition of toxic oxo-anions present in water is a crucial and first step towards environmental remediation, mainly in the case of water pollution. Accordingly, the utilization of luminescent coordination networks has received significant interest, particularly for the recognition of various toxic oxo-anions, which are considered a threat to aquatic life and the environment. In this frontier article, we summarize recent reports on luminescent CPs/MOFs, their utilization for the sensing of oxo-anions and the chemistry of the interaction of oxo-anions with CPs/MOFs, which is responsible for tuning their optical signals.

Selective anions mediated fluorescence "turn-on", aggregation induced emission (AIE) and lysozyme targeting properties of pyrene-naphthalene sulphonyl conjugate

We have designed and synthesized a novel pyrene-naphthalene sulphonyl conjugate, 1-((1Z)-(4-((Z)-4-(pyrene-1-yl)methyleneamino)phenylsulfonyl)phenylimino)methyl)naphthalene-2-ol (PSN) through a facile two-step reactions. It was characterized by various spectral techniques. Fluorescence spectral studies showed that compound PSN featured fluorescence enhancement upon increasing the water content in THF. This can be attributed to the phenomena of aggregated induced emission (AIE), which is confirmed by SEM and AFM studies, due to the restriction of CHN isomerization of PSN. The anion sensing of PSN was examined with various anions. Among these anions, H₂PO₄^- and F^- ions were selectively sensing with a low detection limit of 3.52 × 10^-7 M and 7.23 × 10^-7 M, respectively, and an obvious color change from yellow to orange was observed by the naked eye. The mechanism of sensing involved the formation of hydrogen bonding interaction between O-H group of PSN and H₂PO₄^-/ F^- ions. The binding of PSN with LYZ was also examined by docking studies, which shows that H-bonding and hydrophobic interactions play crucial roles for the interaction of LYZ toward PSN.

pH response of a hydroxyl-functionalized luminescent metal–organic framework based phosphor

The ligand sensitized Tb³⁺ centered emission of Tb-doped Y-based hydroxyl functionalized MOFs has been utilized for pH sensing in the visible range.

A new 2D lanthanum based microporous MOF for efficient synthesis of cyclic carbonates through CO2 fixation

We report a new microporous La-MOF La-5-SIP-MOF through solvothermal reaction and it showed high catalytic activity for the synthesis of cyclic carbonates from epoxides via the CO₂ fixation reaction at room temperature.

Photophysical studies of a room temperature phosphorescent Cd(ii) based MOF and its application towards ratiometric detection of Hg2+ ions in water

A cadmium based MOF showed room temperature phosphorescence and interacted very selectively with Hg²⁺ ions. The phosphorescence emission at 520 nm gradually disappeared while low intensity fluorescence at 383 nm gradually increased.

Crystal structures and the ferroelectric properties of homochiral metal-organic frameworks constructed from a single chiral ligand

MOFs have proven to be promising candidates for designing ferroelectric materials. Herein, two new homochiral MOFs, Co-MOF-1 and Co-MOF-2, have been synthesized using the chiral ligand, HL (HL = phenyl-((pyridin-4-ylmethyl)-amino)-acetic acid), and Co(NO₃)₂·6H₂O. Co-MOF-1 was obtained via a two-step synthetic route involving a hydrogel to Zn-MOF conversion and a dissolution-recrystallization process. Co-MOF-2 was directly synthesized by a coordination reaction between chiral ligand, HL, and Co(NO₃)₂·6H₂O under hydrothermal conditions. We investigate the correlation between the ferroelectric properties of the samples and their crystal structures. The ferroelectric properties of Co-MOF-1 and Co-MOF-2 are drastically different. Indeed, Co-MOF-2 shows an obvious hysteretic behavior, while a clear electric hysteresis loop was not observed for Co-MOF-1. These significant disparities may be attributed to the different molecular dipole moments in Co-MOF-1 and Co-MOF-2. The different octahedral coordination units in the molecular structures of the Co-MOFs may alter the dipole moments of the molecules, resulting in the absence of a hysteresis loop for Co-MOF-1.

Selective fluorescence sensing properties of a novel two-fold interpenetrating coordination polymer

One novel 3D interpenetrated Zn(ii) CP acts as multi-functional chemosensors in detection of acetone, Fe³⁺, Cu²⁺, Cr₂O₇²⁻, CrO₄²⁻ and nitrofurantoin (NFT).

Multi-responsive chemosensing and photocatalytic properties of three luminescent coordination polymers derived from a bifunctional 1,1′-di(4-carbonylphenyl)-2,2′-biimidazoline ligand

Three 3D Zn^II/Cd^II CPs were synthesized to act as multiresponsive luminescent sensors for Fe³⁺, Cr₂O₇²⁻ and NZF antibiotic. The photocatalytic studies indicate that the CPs 1–3 have good photocatalytic capability in degradation of MB.

A multifunctional photochromic metal–organic framework with Lewis acid sites for selective amine and anion sensing

A bipyridinium-based MOF was prepared, which exhibits reversible photochromic properties, good luminescence sensing ability for Cr₂O₇²⁻, and can be considered an excellent colorimetric sensor for the selective detection of amine vapors.