Field-Induced Slow Magnetic Relaxation in an Octacoordinated Fe(II) Complex with Pseudo-D2d Symmetry: Magnetic, HF-EPR, and Theoretical Investigations.

An octacoordinated Fe(II) complex, [FeII(dpphen)2](BF4)2·1.3H2O (1; dpphen = 2,9-bis(pyrazol-1-yl)-1,10-phenanthroline), with a pseudo-D2d-symmetric metal center has been synthesized. Magnetic, high-frequency/-field electron paramagnetic resonance (HF-EPR), and theoretical investigations reveal that 1 is characterized by uniaxial magnetic anisotropy with a negative axial zero-field splitting (ZFS) (D ≈ -6.0 cm-1) and a very small rhombic ZFS (E ≈ 0.04 cm-1). Under applied dc magnetic fields, complex 1 exhibits slow magnetic relaxation at low temperature. Fitting the relaxation time with the Arrhenius mode combining Orbach and tunneling terms affords a good fit to all the data and yields an effective energy barrier (17.0 cm-1) close to the energy gap between the ground state and the first excited state. The origin of the strong uniaxial magnetic anisotropy for 1 has been clearly understood from theoretical calculations. Our study suggests that high-coordinated compounds featuring a D2d-symmetric metal center are promising candidates for mononuclear single-molecule magnets.

Anisotropic Change in the Magnetic Susceptibility of a Dynamic Single Crystal of a Cobalt(II) Complex.

Atypically anisotropic and large changes in magnetic susceptibility, along with a change in crystalline shape, were observed in a CoII complex at near room temperature. This was achieved by combining oxalate molecules, acting as rotor, and a CoII ion with unquenched orbital angular momentum. A thermally controlled 90° rotation of the oxalate counter anion triggered a symmetry-breaking ferroelastic phase transition, accompanied by contraction-expansion behavior (ca. 4.5 %) along the long axis of a rod-like single crystal. The molecular rotation induced a minute variation in the coordination geometry around the CoII ion, resulting in an abrupt decrease and a remarkable increase in magnetic susceptibility along the direction perpendicular and parallel to the long axis of the crystal, respectively. Theoretical calculations suggested that such an unusual anisotropic change in magnetic susceptibility was due to a substantial reorientation of magnetic anisotropy induced by slight disruption in the ideal D3 coordination environment of the complex cation.

Fluorescent Biomass-Based Platform for Detection of ClO- in Cells and Water-Soluble Systems.

The generation and presence of excessive hypochlorous acid derivative ionic form (ClO-) could cause various diseases, such as arteriosclerosis, DNA damage, and cardiovascular illness. It is a critical need to develop a highly sensitive sensor for reliable detection of ClO- in cells and water-soluble systems. In this work, a hydroxyl group has been introduced into the compound 2-amino-3-(((E)-4-(2-(2-(2-hydroxyethoxy)ethyl)-1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinolin-6-yl)benzylidene)amino)maleonitrile (NDC) to increase its solubility in water, at the same time, the hydrazone unit was designed as a specific recognition group for the "off-on" fluorescence probe of ClO-. The probe NDC presents high selectivity, sensitivity, anti-interference, and low detection limit (67 nM) for ClO-. The recognition mechanism that ClO- breaks the C=N bond and forms the fluorescent compound 4-(2-(2-(2-hydroxyethoxy)ethyl)-1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinolin-6-yl)benzaldehyde (ND-3) has been confirmed by time-of-flight mass spectrometry. The probe NDC presents a good performance in the actual test of water samples and can be designed as the test papers for the quick and convenient detection of ClO- range from 0 to 1 µM. Moreover, the practical application was demonstrated by the successful imaging of endogenous and exogenous ClO- in HeLa cells. Our fluorescent biomass-based platform opens vast possibilities for repeatability, sensitivity, and selectivity detection of ClO- in cells and water-soluble systems.

Gellan gum and pullulan-based films with triple functionalities of antioxidant, antibacterial and freshness indication properties for food packaging.

The objective of this research was to fabricate pH-responsive and active films based on gellan gum (GG) and pullulan (PL) with extracts of Broussonetia papyrifera fruits (BPFE) and leaves (BPLE) by a casting method. Results indicated that the extracts had good compatibility with GG and PL, which were uniformly distributed throughout the matrix. The incorporation of BPFE and BPLE increased the thickness, UV-vis barrier property, mechanical strength, thermal stability and moisture content of the films, while decreasing the water contact angle. Notably, the films exhibited enhanced antioxidant properties, with maximum radical scavenging rates of 77.45 % using 2,2 Diphenyl-1-picrylhydrazyl and 66.21 % using 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid). The antibacterial capability of the films also increased significantly after adding BPLE and BPFE. The results of XRD and FTIR showed that BPFE was bound to GG and PL by hydrogen bond. The release behavior of BPFE from the films agreed best with the first-level kinetic model. Furthermore, the films displayed obvious color responses to ammonia gas and different pH environments. Simultaneously, the films were applied to monitor the freshness of Pelteobagrus fulvidraco fish. The color parameters of the films demonstrated high correlations with the freshness indexes measured through standard laboratory procedures.

Optimized mesopores enable enhanced capacitance of electrochemical capacitors using ultrahigh surface area carbon derived from waste feathers.

Porous carbons with high specific surface area are critical engineering materials for current electrochemical capacitors (ECs) technology. Controlling the pore size distribution of porous carbons remains a significant challenge as it is a key aspect in many applications. Herein, we synthesized porous carbon as the electrode material of ECs by means of a two-step synthesis procedure using abandoned feathers as carbon precursor and potassium hydroxide as activating agent. The optimal sample (AFHPC-800-1:3) exhibited an ultra-high specific surface area (SBET) of 3474 m2/g and a huge total pore volume (VT) of 1.82 m3 g-1 as well as abundant small mesopores ranging from 2 to 5 nm in size. The ECs based on the AFHPC-800-1:3 electrode exhibited an ultra-high specific capacitance (Csp) of up to 709F g-1 at 0.5 A g-1. More interestingly, a capacitance of 212F g-1 was retained even at 100 A g-1, demonstrating excellent high-rate capacitive performance. Furthermore, the symmetrical capacitor yielded an excellent energy density of 35.1 Wh kg-1 when the specific power density was 625 W kg-1, substantiating the potential of the small mesopores in promoting the overall capacitance and energy density of electrode materials.

Simultaneously realizing enhancement of sensitivity for freshness monitoring and multinomial properties of carrageenan/konjac glucomannan/blueberry anthocyanin-based intelligent film by diatomite.

Here, highly sensitive blueberry anthocyanin (BBA)-induced intelligent indicating films were fabricated by incorporating a novel composite ingredient, diatomite (DA), into a matrix of konjac glucomannan (KGM), carrageenan (CAR) and BBA. We systematically investigated the effects of introducing DA and BBA on the structure, physical properties, colorimetric response, and practical application of the KGM/CAR film. Our findings revealed that the DA particles and BBA were well-distributed in the KGM/CAR matrix through hydrogen bonding interactions. This distribution significantly improved tensile strength, surface hydrophobicity, thermal stability, and barrier properties of the KGM/CAR film. Notably, the KGM/CAR-based intelligent film loaded with 6 % DA exhibited the most optimal properties. Furthermore, DA exhibited a hierarchical porous structure, enabling the KGM/CAR film to detect volatile amines with heightened sensitivity. When applied to monitor shrimp spoilage in transparent plastic packaging, the color of the composite film underwent remarkable changes from bright pink to bluish violet. These color changes correlated well with the total volatile basic nitrogen (TVB-N) and pH changes in the shrimp, as determined by standard laboratory procedures. Our work presents a promising approach to the development of high-performance and intelligent food packaging materials. These materials hold great potential for practical applications in the field of food packaging.

Hydrogen-bond activated ESIPT in naphthalimide-based fluorescent probe for sensing volatile amines.

Amines levels present important indicative value in food safety and human health. Although they are involved in some normal physiological responses of the organism, their overproduction or intake may cause pathological responses. Herein, we report a recyclable visual packaging bag for volatile amines detections based on the naphthylamide derivative N-S and its positive PL characteristics. Specifically, handmade test strips based on compound N-S have been applied to fish freshness labeling, and the cyclic fumigation experiment shows its restorable PL effect and efficiency. The possible PL transfer mechanism of naphthylamide derivative N-S is uncovered by the density functional theory (DFT) calculation and titration mass spectrometer and 1H NMR. This work expands a conjugation in a molecule by hydrogen-bond activated ESIPT (H-ESIPT) and provides a portable detection method for volatile amines detection.

A tetra-gonal polymorph of bis-[hydro-tris-(pyrazol-1-yl)borato]iron(II).

The title compound, [Fe(C(9)H(10)BN(6))(2)], is a polymorph of a compound reported previously [Oliver et al. (1980 ▶). Inorg. Chem.19, 165-168]. In the previous report, the compound crystallized in the monoclinic space group P2(1)/c (Z = 4), whereas the crystal symmetry of the compound reported here is tetra-gonal (P4(2)/ncm, Z = 4). The mol-ecular structure is comprised of two hydro-tris-(1-pyrazol-yl)borate ligands (Tp(-)) and a central Fe(II) ion, which is coordinated by six pyrazole N atoms from two two Tp(-) ligands, yielding a distorted bipyramidal FeN(6) geometry. The complete molecule exhibits symmetry 2/m.

An efficient hemicyanine dyes-based ratiometric fluorescence probe for sulfur dioxide derivatives in live-cells and seawater.

In life systems, sulfurdioxide (SO2) has very important function in several physiological processes, which can be generated endogenously during the biosynthesis of sulfur-containing amino acids. Herein, a ratiometric fluorescence probe CY carried with the structure of hemicyanine dyes has been developed to track SO2 derivatives through Michael-addition reaction. The solution of CY shows significant changes from yellow to colorless after adding the SO32-/HSO3- in day light within 2 min. Successfully, probe CY can detect SO2 derivatives in living cells and seawater. Furthermore, probe CY also be used to monitor the change of SO2 derivatives in seawater. These results give evidence of the potential application of CY in future biomedical diagnosis and marine environment research.

Covalent modification of black phosphorus with alkoxy groups to improve the solubility and ambient stability.

Black phosphorus (BP), a new 2D material as a layered allotrope of phosphorus, has regained attention due to its outstanding semiconductor characteristics. However, the major hurdles of using few-layer BP for applications are its poor solution processability and low ambient stability. Here, we report a covalent modification of BP nanosheets by a chemical reaction with sodium alkoxide. Fourier transform infrared spectra, Raman spectra, X-ray photoemission spectra and thermogravimetric analyses all confirmed the successful introduction of alkoxy groups on the BP surface with P-O-C bonds, which increased the solubility and ambient stability of BP. The introduced alkoxy groups as soluble side chains on the BP surface not only increase the solubility of BP nanosheets by almost 3 times, but also decrease the degradation ratio of the modified BP by about 2 times because of the encapsulation. In this work we developed a facile synthetic strategy to covalently modify BP by introducing soluble side chains, suggesting an effective way to realize its full potential application in electronics.

A highly sensitive, fast responsive and reversible naphthalimide-based fluorescent probe for hypochlorous acid and ascorbic acid in aqueous solution and living cells.

It is very important to exploit real-time, ultrasensitive and specific visualization detection methods for hypochlorous acid/hypochlorite (HOCl/ClO-) in biological systems as they are the guardians of the human immune system against pathogens invasion. In our work, we designed a novel reversible naphthalimide-based fluorescent probe NAP-OH to recognize HClO/ClO- with a unique selective colorimetric and fluorescent response, a short response time (<8 s) and a high sensitivity (10.3 nM). In addition, NAP-OH exhibits a novel on-off-on fluorescence response to ClO-/ascorbic acid (AA) with good cycle stability. The fluorescence signal is quenched because HClO/ClO- oxidizes the subunit of NAP-OH to the segment 2,2,6,6-tetramethyl-1-oxo-piperidinium in NAP-O, which can be reduced by AA with the recovery of fluorescence. Finally, the confocal fluorescence imaging has been performed, which proves that NAP-OH can satisfactorily monitor intracellular endogenous and exogenous HClO/AA redox cycles.

A novel 1,8-naphthalimide-based Cu2+ ion fluorescent probe and its bioimaging application.

A new 1,8-naphthalimide-based Schiff base compound, named as (Z)-2-butyl-6-(((2-hydroxyphenyl)imino)methyl)-1H-benzo[de]isoquinoline-1,3(2H)-dione (BHBD), has been simply synthesized with high yields. BHBD can be employed as a "turn-on" fluorescent probe for Cu2+ ion with high sensitivity, high selectivity and relatively low detection limit (0.48 × 10-6 M). The fluorescence emission of BHBD is very weak in H2O/THF (v/v: 7/3) mixture, which is significantly enhanced after addition of Cu2+ ion. The proposed mechanism is verified by 1H NMR, Job's plot and TOF-MS experiments. Anti-interference experiment, cytotoxicity assay and pH influence results indicated that BHBD meets the requirements of bioimaging. Therefore, BHBD has been successfully applied in detecting Cu2+ ion in HeLa cells.

Hydrogen-bond directed cyanide-bridged molecular magnets derived from polycyanidemetalates and Schiff base manganese(III) compounds: synthesis, structures, and magnetic properties.

A series of six new cyanide-bridged heterometallic complexes including two tetranuclear T-like Fe(III)Mn(III)(3) compounds, {[Mn(L(1))(H(2)O)](3)[Fe(CN)(5)(1-CH(3)im)]}ClO(4) x 1.5 H(2)O (1) and {[Mn(L(2))(H(2)O)](3)[Fe(CN)(5)(1-CH(3)im)]}ClO(4) x 3 H(2)O (2); two heptanuclear cage-shaped M(III)Mn(III)(6) (M = Fe, Cr) compounds, {[Mn(L(2))(H(2)O)](6)[Fe(CN)(6)]}[Fe(CN)(6)] x 6 CH(3)OH (3) and {[Mn(L(2))(H(2)O)](6)[Cr(CN)(6)]}[Cr(CN)(6)] x 6 CH(3)OH (4); and two two-dimensional M-Mn(III) networks, {[H(3)O][Mn(L(1))](2)[Fe(CN)(6)]} x 2 DMF (5) and {K[Mn(L(1))](2)[Cr(CN)(6)]} x 1.5 CH(3)CN x CH(3)OH (6) (L(1) = N,N-ethylene-bis(3-methoxysalicylideneiminate, L(2) = N,N-ethylene-bis(3-ethoxysalicylideneiminate) have been successfully assembled from three polycyanidemetalates containing five or six cyanide groups and two manganese(III) building blocks containing bicompartmental Schiff base ligands. The cyanide-bridged polynuclear complexes are self-complementary through a coordinated aqua ligand from one complex and the free O(4) compartment from the neighboring complex, giving supramolecular one-dimensional ladders and three-dimensional networks for 1 and 2 and for 3 and 4, respectively. Investigation over magnetic susceptibilities of the six complexes reveals the overall ferromagnetic interactions for complexes 1, 2, 3, and 5 and antiferromagnetic interaction for 4 and 6. Compounds 1-4 show some characteristics of metamagnet behavior at low temperatures due to the relatively strong intermolecular hydrogen-bonding interaction. The two complexes with two-dimensional structure exhibit three-dimensional antiferromagnetic ordering with typical metamagnetic behavior below 8.4 K for 5 and 11.5 K for 6, respectively. The present result appears to add new members to the very few examples of polynuclear clusters exhibiting 3D magnetic ordering relying on intermolecular interactions, to the best of our knowledge, which will be helpful for providing valuable information for the understanding and application of intermolecular hydrogen-bonding interactions in the molecular magnetic materials.

Synthesis, crystal structures, and luminescent properties of phenoxo-bridged heterometallic trinuclear propeller- and sandwich-like Schiff-base complexes.

A series of phenoxo-bridged heterometallic Schiff-base trinuclear complexes Zn-M-Zn [M = Cd(II), Pb(II), Nd(III), Eu(III), Gd(III), Tb(III), and Dy(III)] have been synthesized by a rational structural design based on two symmetrical Schiff-base ligands N,N'-bis(3-methoxysalicylidene)propylene-1,3-diamine (H(2)L(a)) and N,N'-bis(3-methoxysalicylidene)benzene-1,2-diamine (H(2)L(b)). Single X-ray diffraction analysis reveals a similar molecular structure among the eight propeller-like and seven sandwich-type phenoxo-bridged Zn-M-Zn complexes. In the compounds Cd[Zn(L(a))Cl](2) (1), {Cd[Zn(L(b))Cl](2)}.H(2)O (2), {Pb[Zn(L(b))Cl](2)}.2H(2)O (4), {Nd[Zn(L(a))Cl](2)(H(2)O)}.0.5ZnCl(4) .2H(2)O (5), and{M(III)[Zn(L(a))Cl](2)(H(2)O)}.0.5ZnCl(4).2MeOH [M = Eu(7), Gd (9), Tb (11), and Dy (13)], two [Zn(L)Cl](-) units coordinate to the central metal ion as a tetradentate ligand using its four oxygen atoms, forming a two-blade propeller-like left-handed and right-handed chiral Zn-M-Zn configuration despite the racemic nature of the whole complexes. Compounds {Pb[Zn(L(a))Cl](2)}.MeOH (3), {Nd[Zn(L(b))Cl](2)(DMF)(OAc)}.CH(3)CN (6), {Eu[Zn(L(b))Cl](2)(DMF)(OAc)}.CH(3)CN (8), {Gd[Zn(L(b))Cl](2)(DMF)(2)}.Cl.2H(2)O (10), {Tb[Zn(L(b))Cl](2)(DMF)(2)}.Cl.2H(2)O (12), {Dy[Zn(L(b))Cl](2)(DMF)(2)}.Cl.2H(2)O (14), and {Pb[Zn(L(b))Cl](2)}.2H(2)O (15) exhibit a relatively rare sandwich-type structure with a central metal ion clamped by two [Zn(L)Cl](-) units. Photophysical studies indicate that all of the complexes exhibit luminescence both in solution and in solid sate, and there exists an energy transfer from the [Zn(L)Cl](-) unit to the central rare earth ions of Nd(III) (5 and 6), Tb(III) (11), and Dy(III) (for 13). In particular, systematic and comparative investigation of the photophysical properties of these trinuclear complexes reveals that the luminescence properties could easily be tuned by changing the central metal or the Schiff-base ligand.

Rational design and assembly of a new series of cyanide-bridged Fe(III)-Mn(II) one-dimensional single chain complexes: synthesis, crystal structures, and magnetic properties.

Two mononuclear seven-coordinated macrocycle manganese(II) compounds and three dicyanide-containing precursors have been employed as building blocks to assemble cyanide-bridged heterobimetallic complexes, resulting in five new cyanide-bridged single chain complexes {[Mn(L(1))][Fe(bpb)(CN)(2)]}ClO(4) x 0.5 H(2)O (2), {[Mn(L(2))][Fe(bpb)(CN)(2)]}ClO(4) x 0.5 H(2)O (3), {[Mn(L(1))][Fe(bpClb)(CN)(2)]}ClO(4) x H(2)O (4), {[Mn(L(2))][Fe(bpClb)(CN)(2)]}ClO(4) x 0.5 H(2)O (5), and {[Mn(L(1))][Fe(bpdBrb)(CN)(2)]}ClO(4) x H(2)O (6). Single X-ray diffraction analysis reveals their one-dimensional (1D) single cyanide-bridged cationic polymeric chain structure consisting of alternating units of [Mn(L)](2+) (L = L(1) or L(2)) and [Fe(L')(CN)(2)](-) (L' = bpb(2-), bpClb(2-) or bpdBrb(2-)) with free ClO(4)(-) as balanced anion. Similar to the mononuclear macrocyclic manganese(II) precursor {[Mn(L(2))(H(2)O)Cl]ClO(4)}.CH(3)OH (1), the coordination geometry of manganese(II) ion in all the 1D complexes is a slightly distorted pentagonal-bipyrimidal with two cyanide nitrogen atoms at the trans positions and N(5) or N(3)O(2) coordinating mode at the equatorial plane from ligand L(1) or L(2). Investigation of the magnetic properties of these five 1D single chain cyanide-bridged Fe(III)-Mn(II) complexes reveals the antiferromagnetic magnetic coupling between neighboring Fe(III) and Mn(II) ions through the bridging cyanide group. A best-fit to the magnetic susceptibilities of these complexes based on the 1D alternating chain model leads to the magnetic coupling constants J(1) = -1.16(2) and J(2) = -0.10(3) cm(-1) for 2, J(1) = -3.10(1) and J(2) = -0.25(1) cm(-1) for 3, J(1) = -1.10(1) and J(2) = -0.139(8) cm(-1) for 4, J(1) = -1.99(6) and J(2) = -0.57(1) cm(-1) for 5, and J(1) = -1.23(1) and J(2) = -0.13(5) cm(-1) for 6, respectively. This work will provide valuable information for the rational design and synthesis of low-dimensional, in particular, single chain, cyanide-bridged magnetic complexes.

{2,2'-[(5-Bromo-pyridine-2,3-di-yl)bis-(nitrilo-methyl-idyne)]diphenolato}chlorido(N,N-dimethyl-formamide)iron(III).

In the title complex, [Fe(C(19)H(12)BrClN(3)O(2))(C(3)H(7)NO)], the Fe(III) atom is coordinated by an N,N,O,O-tetra-dentate Schiff base ligand and trans coordinated by a chloride anion and the O atom of an N,N-dimethyl-formamide mol-ecule. The resulting geometry is distorted octa-hedral within a ClN(2)O(3) donor set.

4,5-Diamino-benzene-1,2-dicarbonitrile.

The mol-ecular skeleton of the title mol-ecule, C(8)H(6)N(4), is essentially planar [maximum deviation from the mean plane of 0.037 (2) Å]. All N atoms are involved in the formation of inter-molecular N-H⋯N hydrogen bonds. The crystal packing exhibits also dipole-dipole inter-actions between the cyano groups of neighbouring mol-ecules [C⋯C 3.473 (2) Å].

An o-hydroxyl aldehyde structure based naphthalimide derivative: Reversible photochromic properties and its application in ClO- detection in living cells.

A bifunctional organic compound 2-butyl-6-hydroxy-1,3-dioxo-2,3-dihydro-1H-benzo[de] isoquinoline-5-carbaldehyde (BHC) with photochromic properties in solid state and probe detection for ClO- in complete water solution was synthesized and fully characterized. A 'white-yellow-white' reversible photochromic behavior could be observed when alternating UV/vis light irradiation on the solid BHC powder. Good fatigue resistance and adjustable bleaching rate were shown when heating conditions changes. In addition, BHC displayed a high selectivity and low detection limit (1.16 × 10-8 M) for ClO-. The photoluminescent fluorescence "on-off" recognition result can be easily identified and BHC has been tested for safely imaging living cells and detecting hypochlorite anion in vitro and vivo. A better water solubility of BHC effectively reduces damage caused by organic solvent in cell imaging progress.

Bis(diethyl-enetriamine-κN,N',N'')nickel(II) bis-(1,2-dicyanoethene-1,2-dithiolato-κS,S')nickel(II).

The title compound, [Ni(C(4)H(13)N(3))(2)][Ni(C(4)N(2)S(2))(2)], has been synthesized by the reaction of Ni(ClO(4))(2)·6H(2)O, diethyl-enetriamine (deta) and Na(2)[Ni(mnt)(2)] [mnt = maleonitrile-dithiol-ate(2-)] in methanol. The structure is composed of a [Ni(deta)(2)](2+) cation and a [Ni(mnt)(2)](2-) anion. The coordination geometry of the Ni(II) ion in the cation is slightly distorted octa-hedral, defined by six N atoms from two deta ligands, while the Ni(II) ion in the anion is four-coordinated by four S atoms from two mnt ligands in a slightly distorted square-planar geometry. The cations and anions are connected by N-H⋯N hydrogen bonds.

A series of 4,5,9,10-tetrahydropyrene-based tetraarylethenes: synthesis, structures and solid-state emission behavior.

By controlling the number of 4,5,9,10-tetrahydropyrene segments around the tetraarylethene core, a series of 4,5,9,10-tetrahydropyrene-based tetraarylethenes were synthesized and structurally characterized. An aggregation-induced emission (AIE) study indicated that all the compounds are AIE active: they are weak emitters in good solvents but highly emissive in the condensed phase, and hence are potential solid-state emitters. Their optical properties, electrochemical properties and theoretical calculations were investigated, and the results prove that the π-conjugation degree of these compounds increases with the increasing number of 4,5,9,10-tetrahydropyrene units. However, the fluorescence quantum yield in the solid state doesn't increase with increasing π-conjugation. We studied the reason for this by analyzing the crystal structures of some compounds, and proposed that the close degree of molecular packing in the solid state may be responsible for it. Loose packing of tetraarylethenes in the solid state can restrict the rotation of the aromatic rings but cannot constrain other non-radiative pathways efficiently, such as vibration, which leads to the unpredictable emission of the compounds.