Solid State Research Articles

Room‐Temperature Phosphorescence of Cocrystals of Aromatic Bisimides and Triplet Sensitizer Pt(acac)2

AbstractFour sterically shielded aromatic bisimides are synthesized and their ability to form cocrystals with the triplet sensitizer platinum(II) acetylacetonate (Pt(acac)2) is investigated. Single crystals of the individual electron‐deficient bisimides are studied first, two showing bright blue fluorescence with quantum yields of up to 28%, while the other two barely emit at all. After successful cocrystallization of all four aromatic bisimides with the electron‐rich Pt(II) complex, two different stoichiometries, either 1:1 or 1:2, are found in the crystalline solid state, whose absorbance and photoluminescence exhibit distinct bathochromic shifts. While two naphthalene bisimides show strong and long‐lived room‐temperature phosphorescence (RTP) with quantum yield exceeding 50%, the other two aromatic bisimides show only minor photoluminescence at RT, but a bright low‐temperature phosphorescence (LTP) at 80 K. Theoretical calculations reveal the importance of changing the magnetic quantum number ml of the involved d‐orbitals at the platinum center as well as the alignment of the Pt(II) center above an aromatic C─C bond for an efficient intersystem crossing in these hybrid systems.

Unraveling Interdiffusion Phenomena and the Role of Nanoscale Diffusion Barriers in the Copper-Gold System.

Diffusion is one of the most fundamental concepts in materials science, playing a pivotal role in materials synthesis, forming, and degradation. Of particular importance is solid state interdiffusion of metals which defines the usable parameter space for material combinations in the form of alloys. This parameter space can be explored on the macroscopic scale by using diffusion couples. However, this method reaches its limit when going to low temperatures, small scales, and when testing ultrathin diffusion barriers. Therefore, this work transfers the principle of the diffusion couples to small scales by using core-shell nanowires and in situ heating. This allows us to delve into the interdiffusion dynamics of copper and gold, revealing the interplay between diffusion and the disorder-order phase transition. Our in situ TEM experiments in combination with chemical mapping reveal the interdiffusion coefficients of Cu and Au at low temperatures and highlight the impact of ordering processes on the diffusion behavior. The formation of ordered domains within the solid-solution is examined using high-resolution imaging and nanodiffraction including strain mapping. In addition, we examine the effectiveness of ultrathin Al2O3 barrier layers to control interdiffusion of the diffusion couple. Our findings indicate that a 5 nm thick layer serves as an efficient diffusion barrier. This research provides valuable insights into the interdiffusion behavior of Cu and Au on the nanoscale, offering potential applications in the development of miniaturized integrated circuits and nanodevices.

Triethanolamine-modified poloxamer temperature-sensitive hair care gel for intelligent controlled release of sodium thioglycolat

Abstract A triethanolamine-modified poloxamer temperature-sensitive hair care gel was formulated in order to reduce the adverse health effects associated with sodium thioglycolate (TGA(Na)), the active component in hair treatment agents, while maintaining excellent efficacy. It was found that TEA-3 gelled at 32 °C with a triethanolamine concentration of 3 %. This formulation exhibited a reversible phase transition, transitioning to a solid state upon contact with the scalp (>32 °C) and reverting to a liquid state when in contact with hair (<32 °C). The release behavior of TGA(Na) from the gel was assessed by both in vitro release studies and transdermal experiments. In addition, it was observed that the triethanolamine-modified poloxamer gel exhibited improved hair care efficiency compared to conventional hair care agents. These results suggest that the triethanolamine-modified poloxamer gel is a promising alternative to conventional hair care products, offering improved efficacy while minimizing potential adverse health effects.

Space‐ and Time‐resolved Emission Features of Micro‐ and Nano‐sized Perylene‐based Zr Metal‐Organic Frameworks

AbstractWhile many photoresponsive metal‒organic frameworks (MOFs) have been reported to date, finding applications in several technologically relevant fields such as photocatalysis, sensors, and light‐emitting devices, significantly scarcer are the reports addressing the relationship between the MOFs emissive features and their crystalline domain size (i.e., micro‐ and nano‐sized materials). Herein, a valuable contribution is offered to this issue which consists of the use of reticular chemistry to prepare a Zr‐MOF featuring spatially separated tetracarboxylated‐functionalized perylenes as ligand. Single crystal X‐ray analysis of such Zr‐MOF revealed the formation of micro‐ and meso‐porous channels. The perylene‐based Zr‐MOF exhibited notable optoelectronic features, including a relatively small optical bandgap of 1.82 eV and emission features different from that of the constituting perylene ligand in the solid state. Additionally, local probe techniques are used to unveil the emission properties of isolated Zr‐MOF crystals. Space‐ and time‐resolved fluorescence studies revealed a strong dependence of the emissive features of the Zr‐MOF, both in terms of its intensity and lifetime, to the crystalline domain size.

Re-examination of the intumescence mechanism of fire retarded PP with APP/pentaerythritol/zeolite-4A using advanced spectroscopic techniques

The mixture of ammonium polyphosphate (APP) and pentaerythritol (PER) is a very efficient flame retardant (FR) intumescent system suitable for polyolefins such as polypropylene (PP). The mechanisms of intumescence of this FR system in this polymer was investigated using different spectroscopic techniques including continuous wave (CW) electron paramagnetic resonance (EPR) spectroscopy and solid state nuclear magnetic resonance (NMR) technique. In this work, the intumescence mechanism of PP/APP/PER formulations with and without 4A is revisited. The intumescent system was in-depth investigated using NMR, CW EPR and pulsed EPR. The CW EPR technique confirmed that free radicals are mainly generated during the intumescence of the system between 250 and 350 °C. Thanks to the pulsed EPR and solid state NMR, it was evidenced that a key structural shift from a predominantly carbonaceous residue to a predominantly phosphorated residue. Besides, it was also evidenced that zeolite 4A totally collapses during extrusion of PP/APP/PER formulations reacting with APP to generate aluminophosphates. Then, silicophosphates are generated between 350 and 400 °C. Both alumino- and silicophosphates contribute to protect aromatic structures in the residue at high temperatures.

Structural, morphological and photoluminescence studies of Ca7Mg2P6O24:RE3+(RE3+= Tb3+, Dy3+) nanophosphor for solid state illumination

The Ca7Mg2P6O24:RE3+ (RE3+= Tb3+, Dy3+) nanophosphor material was synthesized by traditional wet chemical method. The XRD are used to determine phase and crystallinity of the synthesized sample; further FTIR, SEM, TEM, and PL properties were studied. The XRD pattern of prepared sample match well with standard JCPDS card no 00–020–0348, and it exhibits the rhombohedral structure along with space group R3c (161). The phosphate (PO4)3-group absorption band was observed at 990–1100 cm-1 in FTIR. Surface morphology (TEM analysis) reveals particle sizes in the range of 55–110 nm. The luminescence emission spectra of Ca7Mg2P6O24 phosphor activated by Tb3+ were studied at three different excitations: 352 nm, 370 nm, and 379 nm. The spectra show two emission peaks at 470 nm (blue) and 545 nm (green). These are due to the 5D4 → 7F6 and 5D4 → 7F5 transitions of Tb3+ ions. The highest intensity peak is located at 545 nm. The Ca7Mg2P6O24:Tb3+ phosphor's CIE chromaticity coordinates are (0.040, 0.316) at 491 nm and (0.265, 0.724) at 543 nm. These are in the blue and green areas on the edges of the CIE diagram, respectively. The photoluminescence emission spectra of Dy3+-doped Ca7Mg2P6O24 phosphor show two significant emission peaks located at 482 nm and 574 nm. These are caused by the 4F9/2 → 5H15/2 and 4F9/2 → 6H13/2 transitions of Dy3+ ions, which produce blue and yellow light, respectively, with an excitation wavelength of 350 nm. The sharp peak position at 482 nm produces the strongest emission. The effect of concentration quenching in between the Dy3+-Dy3+ions and Tb3+-Tb3+ ions is due to dipole-dipole interaction. The CIE color coordinate is found to be (0.082, 0.156) at 482 nm and (0.471, 0.527) at 574 nm which lies in blue and yellow border of CIE diagram. The lifespan of Tb3+, Dy3+activated Ca7Mg2P6O24 nanophosphor of highest concentration is found to be 1.917 ms and 0.9985 ms respectively. On investigation, the synthesized Tb3+, Dy3+activated Ca7Mg2P6O24 nanophosphor can be potential for solid lightning devices & other display application.

Enhanced functionalities of isovalently substituted 0.67(Bi1-xLaxFe0.97Ga0.03O3)-0.33(BaTiO3) relaxor piezoceramics synthesized via air quenching

The isovalently substituted lead-free binary solid solution, 0.67(Bi1-xLaxFe0.97Ga0.03O3)-0.33(BaTiO3) (BF-BT) (x ≤ 0.07), has been synthesized by solid state ceramic method via air quenching sintering. FTIR and XRD along with Rietveld structure refinement confirmed a pure perovskite phase with a pseudocubic structure (space group Pm3‾m) for developed compositions. SEM revealed a dense microstructure with fine grain size (<1.5 μm) and minimal porosity. XPS analysis reveals predominantly Bi+3 and Fe+3 states, along with oxygen vacancies (VO··). Ferroelectric studies demonstrated a maximum remanent polarization (Pr) of 12.3 μC/cm2 and coercive field EC of 30.95 kV/cm for La3+ concentration of x = 0.03. Overall decrement in Pr can be attributed to dipolar defect-induced random fields reducing the activation barrier for domain nucleation. Leakage current measurement reveals improved resistivity (∼108 Ω cm) up to an applied field of 30 kV/cm. Dielectric measurements unveiled two frequency-dependent anomalies in temperature dependence above room temperature, indicative of diffuse phase transitions. The Vogel-Fulcher model depicted an increasing freezing temperature (from 465 K for x = 0.01–551 K for x = 0.07) and decreasing activation energy (from ∼0.61 eV to 0.07 eV) with increasing La3+ concentration. The estimated diffuseness parameter around ∼2 suggested relaxor behavior. Doping with La resulted in increased dielectric permittivity at 10 kHz (from 4100 to 24066), showcasing the efficacy of site engineering in augmenting the functional properties of BF-BT for high-temperature dielectric and transducer applications.

Influence of the Constant Magnetic Field on the Density of an Aging Alloy of Beryllium Bronze BrB-2

This paper presents the main experimental results of measuring the density of beryllium bronze BrB-2, aged in the constant magnetic field and in its absence, using the hydrostatic weighing method. The temperature and time dependences of the density of beryllium bronze BrB-2 during the decomposition of a supersaturated solid solution in a constant magnetic field of strength 557.2 kA/m were studied, at aging temperatures of 250, 300, 350 and 400°C and aging duration from 0 to 1 hour, and a comparative comparison analysis of their behavior with the corresponding microhardness dependencies was carried out. The correlation was discovered between the temperature and time dependences of the density and microhardness of beryllium bronze BrB-2, so at an aging temperature of 350°C a sharp maximum in the density of the alloy is observed, and similarly, at the same point the absolute maximum microhardness is achieved. In addition, it was found that the application of a constant magnetic field to the aging process under all heat treatment modes always leads to an increase in the density and microhardness of beryllium bronze BrB-2 compared to the density of the alloy aged in its absence. A physical interpretation is given to the observed facts and patterns. In the future, it is planned to find a correlating function between two independent measured characteristics density and microhardness, which is important for solid state physics and materials science from a scientific and practical point of view.

Oleo-extraction of microplastics using flotation plus sol-gel technique to confine small particles in silicon dioxide gel.

Extracting microplastics from natural sources is challenging, especially microplastics with sizes smaller than 100μm. The flotation method is the most common microplastic extraction, but it struggles with fine particles due to the difficulty in collecting floating plastic particles from the liquid during the separation process. This study proposes a new floating media, tetraethyl orthosilicate (TEOS), that could separate microplastics using its hydrophobic-oleophilic properties. Most interestingly, TEOS transformed from a liquid state to a solid state (gel) by hydrolysis and condensation reactions, thus safely capturing the separated microplastic particles after flotation and mitigating particle loss from scooping since its gel acted as a particle holder. The average recovery rates obtained were in the range of 95-100% for polyethylene terephthalate, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polytetrafluoroethylene, and aged tyre rubber. The recovery rates were slightly reduced for finer particles (sizes down to 40μm) at 82-98%. TEOS-based extraction provided a higher recovery rate for non-polar plastics than for polar or hydrophilic plastics. The separated microplastics maintained their characteristics for polymer identification, as proven by spectroscopic and thermal analysis techniques. Therefore, TEOS-based extraction could be a new approach to microplastic extraction, especially for preventing fine particle loss.

Eu(III) complexes derived from 2-quinolinecarbohydrazide Schiff base ligand, relations between structure and luminescence properties

A series of Eu(III) complexes were obtained following the template condensation of 2-quinolinecarbohydrazide and 2,6-diacetylpyridine, namely: [Eu(H2pbqh)(NO3)3]·MeOH (1), [Eu(Hpqh)(NO3)3]·2MeCN (2), [Eu(H2pbqh)(SCN2)(MeOH)2](SCN) (3) and [Eu2(pbqh)2(NO3)2(H2O)2]·2.5MeOH (4). The structures of complexes and a new H2pbqh ligand (N',N'''-((1E,1′E)-pyridine-2,6-diylbis(ethan-1-yl-1-ylidene))bis(quinoline-2- carbohydrazides)) were elucidated by single-crystal X-ray diffraction. H2pbqh coordinate pentadentate ONNNO and forms mononuclear complexes 1 and 3. The bis-deprotonated ligand pbqh2- act as hexadentate/bridging mode generates the binuclear complex in 4. The partially condensed ligand Hpqh, tetradentate ONNO, was recorded in complex 2. The crystallographic results reveals that the coordinated H2pbqh/Hpqh ligands and Eu3+ cation form a planar structure in these complexes and nitrate anions coordinate chelate, completing the coordination sphere of Eu3+. The solid state photoluminescent emission was investigated highlighting the nitrate complexes 1 and 2 that exhibit red intense luminescence (λmax = 618 nm). Moreover, the computational calculations reveal different pathways of energy transfer from ligand to Eu3+ electronic states explaining the luminescent behavior.

Long Stability of Atomically Precise Red Emissive Copper Nanoclusters within the Gel and Their Use As a Potential Catalyst and Fluorescent Ink.

Herein, an amphiphile-based hydrogel (with 5% DMF) containing natural amino acid residue has been used to prepare and stabilize red-emitting CuNCs for several months. Though different methods have been attempted, amphiphile and 4-mercaptobenzoic acid (4-MBA)-containing hydrogels are pinpointed to be the base medium to stabilize this new Cu-cluster. From a MALDI-TOF MS analysis it was found that it is a Cu8-atom cluster stabilized by three 4-MBA ligands. Copper acetate monohydrate (Cu(CH3COO)2·H2O) has been used as a copper precursor, and l-ascorbic acid has been used as a reducing agent. FEG-TEM analysis shows that the Cu cluster has an average size of 2.83 nm. Interestingly, these clusters can be used as a fluorescent ink with a visibility of the solid state under a UV-lamp with an excitation of 365 nm. This envisaged applying these CuNCs for anticounterfeiting. These Cu-clusters show an excitation of 420 nm with an emission of 620 nm, as is evident from the fluorescence spectroscopic analysis. Based on our knowledge, this is the first example of making and consequently stabilizing Cu-clusters using hydrogel as a template for a few months. Moreover, these CuNCs can also be used as a catalyst for the reduction of nitro derivatives to their amine derivatives in aqueous medium.

Synthesis and Properties of Tris(3‐Pyrrolyl BODIPY) on 1, 3, 5‐Triazine Scaffold

AbstractTris(3‐pyrrolyl BODIPY) on 1,3,5‐triazine scaffold was synthesized over a sequence of steps starting from commercially available cyanuric chloride. The cyanuric chloride was reacted with p‐hydroxy benzaldehyde to afford 1,3,5‐triazine tris(p‐oxybenzaldehyde) which was then reacted with excess pyrrole under acid catalyzed conditions to afford 1,3,5‐triazine‐tris(meso‐p‐oxyphenyl dipyrromethane). Subsequent in situ oxidation of this compound with DDQ to obtain tris(meso‐oxyphenyldipyrromethene) which was then treated with pyrrole followed by the addition of Et3N/BF3 ⋅ OEt2 afforded fluorescent tris(3‐pyrrolyl BODIPY). For comparison, tris(BODIPY) on the triazine scaffold was prepared by oxidizing tris(meso‐oxyphenyldipyrromethane) with DDQ followed by complexation with BF3 ⋅ OEt2. Both compounds were thoroughly characterized and studied by various experimental and theoretical methods. Absorption, steady state fluorescence, time‐resolved fluorescence, and transient‐absorption studies revealed that in tris(3‐pyrrolyl BODIPY), excitonic interactions between two of the three 3‐pyrrolyl BODIPY units resulted in a hypsochromic shift in spectral bands, reducing the quantum yield and singlet state lifetime whereas tris(BODIPY) did not show such excitonic interactions. DFT studies helped in understanding the excitonic interactions in tris(3‐pyrrolyl BODIPY). The tris(3‐pyrrolyl BODIPY) was fluorescent both in solution and solid state. The viscosity studies indicated that the fluorescence of tris(3‐pyrrolyl BODIPY) increases significantly with solvent viscosity, suggesting its potential for measuring cellular viscosity during physiological processes.

Vibrational squeezing via spin inversion pulses

Magnetic resonance force microscopy (MRFM) describes a range of approaches to detect nuclear spins with mechanical sensors. MRFM has the potential to enable magnetic resonance imaging with near-atomic spatial resolution, opening up exciting possibilities in solid state and biological research. In many cases, the spin-mechanics coupling in MRFM is engineered with the help of periodic radio frequency pulses. In this paper, we report that such pulses can result in unwanted parametric amplification of the mechanical vibrations, causing misinterpretation of the measured signal. We show how the parametric effect can be canceled by auxiliary radio frequency pulses or by appropriate post-correction after careful calibration. Future MRFM measurements may even make use of the parametric amplification to reduce the impact of amplifier noise.

Cationic or Neutral: Dependence of Photophysical Properties of Bis-Alkynylphosphonium Pt(II) Complexes on Ancillary Ligand.

A series of D-π-A alkynylphosphonium salts with different linker between donor and acceptor groups was used to synthesize two series of trans-bis-alkynylphosphonium Pt(II) complexes with different ancillary ligands (triphenylphosphine, P series, and cyanide, CN series). The nature of the ancillary ligand manages the overall charge and emission properties of the complexes obtained. In addition, the variation of the linker in alkynylphosphonium ligands allows fine-tuning the luminescence wavelength. Dicationic series P is unstable in solution under UV excitation, whereas in the solid state, these complexes are the first example of phosphorescent trans-phosphine-bis-alkynyl Pt(II) compounds. Neutral series CN demonstrates bright emission in solution, including dual emission for 2CN complex with biphenyl linker in alkynylphosphonium ligand. However, in the solid state for the CN series drastic decrease in the emission quantum yield compared to the P series was observed. DFT calculations reveal the complicated emission nature for the both P and CN series with various contributions of 3ILCT, 3LLCT and 3MLCT states. However, in the naphthyl-containing derivatives 3P and 3CN, the dominating 3LC character with some admixture of CT states is postulated.

Metal Oxalates as a CO2 Solid State Reservoir: The Carbon Capture Reaction

Metal Oxalates as a CO2 Solid State Reservoir: The Carbon Capture Reaction

Thermal experiment study on the self-luminous properties of metallic iron during solid–liquid phase transition

According to the thermal experiment study of the self-luminescence spectrum of industrially pure iron (DT8) at a heating and cooling rate of 5 °C/min, at the moment of 0 (800 °C), DT8 had no significant self-luminescence characteristics in the wavelength range of 200–1100 nm. At the same time, the first-order differentiation of the spectral intensity versus time was equal to zero at the beginning and end moments of the solid-liquid phase transition. When the solid-liquid melt temperatures are equal (i.e. 1531 °C), there are two sharp peaks at wavelengths of 589.1 nm and 766.7 nm of the self-luminous spectrum in the pure liquid state compared to the self-luminous spectrum in the pure solid state. The intensity of the spectrum decreases significantly as the metallic iron changes from the pure solid phase to the pure liquid phase, with a reduction rate greater than 20%. The appearance of the fitted peaks at 589.1 nm and 769 nm was found by XPS fitting analysis to be a significant feature of the difference in the auto-luminescence spectra of pure solid phase and pure liquid phase metallic iron at a constant melt pool temperature. After the transformation of pure solid phase into pure liquid phase, the decay rate of the self-luminous spectrum in the long-wave direction at wavelengths greater than 762 nm is greater than that in the short-wave direction at wavelengths less than 625 nm.

A tale of two old drugs tetracycline and salicylic acid with new perspectives—Coordination chemistry of their Co(II) and Ni(II) complexes, redox activity of Cu(II) complex, and molecular interactions

Extensive use of the broad-spectrum tetracycline antibiotics (TCs) has resulted their wide spread in the environment and drive new microecological balances, including the infamous antibiotic resistance. TCs require metal ions for their antibiotic activity and resistance via interactions with ribosome and tetracycline repressor TetR, respectively, at specific metal-binding sites. Moreover, the Lewis-acidic metal center(s) in metallo-TCs can interact with Lewis-basic moieties of many bioactive secondary metabolites, which in turn may alter their associated chemical equilibria and biological activities. Thus, it is ultimately important to reveal detailed coordination chemistry of metallo-TC complexes. Herein, we report (a) conclusive specific Co2+, Ni2+, and Cu2+-binding of TC revealed by paramagnetic 1H NMR, showing different conformations of the coordination and different metal-binding sites in solution and solid state, (b) significant metal-mediated activity of Cu-TC toward catechol oxidation with different mechanisms by air and H2O2 (i.e., mono- and di-nuclear pathways, respectively), (c) interactions of metallo-TCs with bioactive salicylic acid and its precursor benzoic acid, and (d) noticeable change of TC antibiotic activity by metal and salicylic acid. The results imply that TCs may play broad and versatile roles in maintaining certain equilibria in microecological environments in addition to their well-established antibiotic activity. We hope the results may foster further exploration of previously unknown metal-mediated activities of metallo-TC complexes and other metalloantibiotics.

Preparation and Characterization of Novel α-Naphthol Luminophors for Optoelectronic Devices.

Luminophors of α-Naphthol doped with varying concentrations of anthracene and perylene were prepared by conventional solid state reaction method to explore its fluorescence characteristics. The fluorescence spectra of bicomponent and tricomponent luminophors reveals the fluorescence excitation energy transfer (FRET) process. The prepared bi and tri component luminophors were excited at 290nm which corresponds to host excitation wavelength. The weak violet fluorescence of host, α-Naphthol, gets quenched and give anthracene like emission in bicomponent luminophor systems. Further doping with second host, perylene, in anthracene containing α-Naphthol luminophors, red shifted emission was observed at 605nm. The structural parameters, thermal stability and electrical properties of doped luminophors were studied by using X-ray diffraction, TGA-DSC and Cyclic Voltammetry respectively. The particle size of the prepared luminophors was confirmed by scanning electron microscopy (SEM).

Molecular recognition of halogen-bond of Diiodine with an Ambidentate ligand: Fluorometry as lead strategy for analysis in solution

Chemical connectivity of halogen bond (XB) of the diiodine with an ambidentate ligand of the N1-aryl-2-(trifluoromethyl)benzo[b][1,8]naphthyridin-4(1H)-one in solution and in solid state was presented. The organic ligand was characterized by featuring four basic moieties with different hardness (N-heteroarene, ketonic oxygen, methoxy oxygen and π-arene). The study in solution was performed through a simple steady state fluorescence measurements taking advantage on the use of a donor-acceptor (D-A) fluorophore having two key characteristics (i) presence of basic groups along the d-A chain and, (ii) a fluorescence dependent on an intramolecular charge-transfer (ICT) mechanism. It allowed us to distinguish unequivocally the binding preference of the ambidentate ligand toward the diiodine from the recognition of specific dye-fluorescence responses (ICT-quenching, ICT-enhancement, etc.). Fluorometric studies allowed us to elucidate that the diiodine interacts dominantly through the borderline function (N-heteroarene) of ligand under a wide range of diiodine concentration and discretely through the harder ketonic oxygen. UV–Vis spectroscopic confirmed the binding of the diiodine through N-arene moiety, giving typical association constants of 20–40 M-1 for the tested ambidentate ligands. Additionally, the fluorometry allowed us to verify the reversibility of the XB in solution through synchronized radioactivity- and absorption-fluorescence experiments based on nuclear and chemical decomposition of the diiodine, respectively, where the total recovery of the ICT-fluorescence, which was quenched under diiodine binding, confirmed the reversibility of the XB. Further studies in solid state (Raman spectroscopy) confirmed the binding preference of the diiodine toward the borderline N-arene. Experimental evidences of XB were supported and interpreted from DFT-calculations.

The crystal structures of Imine-Enamine ‘tautomerism’ in solid state and “turn on” sensing for Zn2+: spectroscopy, DFT and cell imaging studies

The crystallographically established ligand 2-((E)-(benzyl imino)methyl)-4-bromophenol (HL) (existing keto at 296 K and enol at 120 K in the solid state), which is in equilibrium of interconversion (ΔE) = 4.39Kcal) with its tautomer, showed weak emission in the excited state, due to the fact of PET but in the presence of Zn2+, PET was blocked and chelation-enhanced fluorescence (CHEF) was set up. It exhibits 'turn on' sensor with the coordination of Zn2+. Among various metal ions, the synthesised probe HL selectively detected Zn2+ and LOD was about to ∼ 1.63 µM. The Zn(II) coordinated complex and the relative stabilities of the tautomers of HL were thoroughly calculated by spectroscopic and computational studies. Furthermore, cell imaging was also performed to validate the sensing property as well as cyto-toxicity of the probe.