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The CASSCF, DFT and MR-CI methods are used to investigate the photodissociation of aqueous formic acid. The polarizable continuum model is used to show that solvent effects are a combination of the hydrogen-bonding interaction from explicit [H.sub.2]O molecules and the effects from the bulk surrounding [H.sub.2]O molecules.

Single-molecule magnets (SMMs) with a large spin reversal barrier have been recognized to exhibit slow magnetic relaxation that can lead to a magnetic hysteresis loop. Synthesis of highly stable SMMs with both large energy barriers and significantly slow relaxation times is challenging. Here, we report two highly stable and neutral Dy(III) classical coordination compounds with pentagonal bipyramidal local geometry that exhibit SMM behavior. Weak intermolecular interactions in the undiluted single crystals are first observed for mononuclear lanthanide SMMs by micro-SQUID measurements. The investigation of magnetic relaxation reveals the thermally activated quantum tunneling of magnetization through the third excited Kramers doublet, owing to the increased axial magnetic anisotropy and weaker transverse magnetic anisotropy. As a result, pronounced magnetic hysteresis loops up to 14 K are observed, and the effective energy barrier (Ueff = 1025 K) for relaxation of magnetization reached a breakthrough among the SMMs. [ABSTRACT FROM AUTHOR]

A stable DyIII-dispersed compound with single-molecule magnet behavior, Dy0.06Y0.94(OH)CO3, was isolated by a general strategy targeted at the doping of paramagnetic Dy3+ into a diamagnetic 3D inorganic network of Y(OH)CO3. The single-ion origin of slow magnetic relaxation was gradually released as variations of the dysprosium/yttrium ratio and finally gave a relatively large spin-reversal barrier around 200 K and high hysteresis temperature of 8 K. This study opens up new opportunities to investigate the slow magnetic relaxation and magnetostructural correlation by choosing a suitable inorganic architecture with strong axial anisotropy. [ABSTRACT FROM AUTHOR]

Single-molecule magnets (SMMs) that can be trapped in one of the bistable magnetic states separated by an energy barrier are among the most promising candidates for high-density information storage, quantum processing, and spintronics. To date, a considerable series of achievements have been made. However, the presence of fast quantum tunnelling of magnetization (QTM) in most SMMs, especially in single-ion magnets (SIMs), provides a rapid relaxation route and often sets up a limit for the relaxation time. Here, we pursue the pentagonal bipyramidal symmetry to suppress the QTM and present pentagonal bipyramidal Dy(III) SIMs [Dy(Cy3PO)2(H2O)5]Cl3·(Cy3PO)·H2O·EtOH (1) and [Dy(Cy3PO)2(H2O)5]Br3·2(Cy3PO)·2H2O·2EtOH (2), (Cy3PO = tricyclohexyl phosphine oxide). Magnetic characterizations reveal their fascinating SMM properties with high energy barriers as 472(7) K for 1 and 543(2) K for 2, along with a record magnetic hysteresis temperature up to 20 K for 2. These results, combined with the ab initio calculations, offer an illuminating insight into the vast possibility and potential of what the symmetry rules can achieve in molecular magnetism. [ABSTRACT FROM AUTHOR]

Two new oxalate-bridged Gd(III) coordination polymers, namely, (choline)[Gd(C2O4)(H2O)3Cl]Cl·H2O (1) and [Gd(C2O4)(H2O)3Cl] (2), were first obtained ionothermally by using a deep eutectic solvent (DES). The magnetic studies and heat capacity measurements reveal that the two-dimensional Gd(III)-based coordination polymer of 2 has the higher magnetic density and exhibits a larger cryogenic magnetocaloric effect (MCE) (ΔSm = 48 J kg-1 K-1 for ΔH = 7 T at 2.2 K). [ABSTRACT FROM AUTHOR]

For self-assembled nanocrystals in three-dimensional(3D) superlattices,called supracrystals, the crystalline structure of the metal nanocrystals(either single domain or polycrystalline) or nanocrystallinity islikely to induce significant changes in the physical properties. Previousstudies demonstrated that spontaneous nanocrystallinity segregationtakes place in colloidal solution upon self-assembling of 5 nm dodecanethiol-passivatedAu nanocrystals. This segregation allows the exclusive selection ofsingle domain and polycrystalline nanoparticles and consequently producingsupracrystals with these building blocks. Here, we investigate theinfluence of nanocrystallinity on different properties of nanocrystalswith either single domain or polycrystalline structure. In particular,the influence of nanocrystallinity on the localized surface plasmonresonance of individual nanocrystals dispersed in the same dielectricmedia is reported. Moreover, the frequencies of the radial breathingmode of single domain and polycrystalline nanoparticles are measured.Finally, the orientational ordering of single domain nanocrystalsmarkedly changes the supracrystal elastic moduli compared to supracrystalsof polycrystalline nanocrystals. [ABSTRACT FROM AUTHOR]

The combination of magnetic interaction with high magnetic anisotropy provides a promising way for modulating/fine-tuning molecular magnetic behaviors. Here, we show the building block approach for the synthesis of a family of dilanthanide single-molecule magnets (SMMs) bridged with a cyanometallate starting from a monolanthanide SMM. Contingent on the central para-/diamagnetic [M(CN) 6 ] 3- (M = Fe, Co) integrated between two highly anisotropic pentagonal-bipyramid Dy(III) subunits, the remanence of magnetization is OFF/ON below 15 K and they respectively display a record reversal barrier of 659 K among d-f SMMs and 975 K among cyano-bridged SMMs.

The inadequate rheological properties limit the film blowing process of biodegradable polylactic acid (PLA), thus hindering its potential application in environmentally friendly packaging films and mulch films. Herein, biodegradable polyethylene glycol (PEG) and d-lactide were used to synthesize three kinds of poly-d-lactic acid (PDLA)- b -PEG- b -PDLA (DPD) triblock copolymers, and their effects on stereocomplex (sc) structure formation and rheological properties of the composites were studied. The results showed that the poly l-lactic acid (PLLA)/DPD4k sample introduced the highest sc content, storage modulus, and complex viscosity value compared with PLLA/DPD2k and PLLA/DPD10k at the same loading condition, indicating that the PEG4k chains can better accelerate the formation of a sc network between DPD4k and the PLLA matrix. The introduction of 10 wt % DPD4k also resulted in about 38 times longer relaxation time and a strain-hardening behavior during the steady biaxial extension of PLLA. At last, the continuous film blowing process was successfully conducted in the PLLA/DPD4k composites, which acquired a stable blow-up ratio of 3.07. On the basis of the above results, the soft chain-grafted PDLA copolymer may provide a novel method for film blowing of biodegradable PLA., Competing Interests: The authors declare no competing financial interest.

The abuse of traditional antibiotics has caused a series of health problems including antimicrobial resistance, which threatens human health. Therefore, searching for broad sources of antimicrobial agents and developing multidimensional strategies to combat bacterial infections are urgent. Here, we reported two natural self-assembling modes between berberine (BBR) and flavonoid glycosides: nanoparticles (NPs) and nanofibers (NFs), which were both mainly governed by electrostatic and hydrophobic interactions. These two nanostructures exhibited different antibacterial properties from BBR. NPs showed significantly enhanced bacteriostatic activity, whereas NFs displayed a much weaker effect than BBR. The distinguishing properties can be attributed to the different spatial configurations and self-assembly processes of NPs and NFs. Flavonoid glycosides and BBR first formed a one-dimensional complex unit and subsequently self-assembled into three-dimensional nanostructures. With the hydrophilic glucuronic acid toward the outside, NPs exhibited stronger affinity to bacteria, thereby inducing the collapse of the bacteria population and the decrease in biofilm. In addition, in vitro hemolysis tests, cytotoxicity tests, and in vivo zebrafish toxicity evaluation showed that the obtained self-assemblies had good biocompatibility. This supramolecular self-assembly strategy can be applied to construct other nanoscale antibacterial drugs and thus provides weapons for the development of self-delivering drugs in bacterial infection treatment.

Two structurally intriguing dysprosium(III)-substituted polyoxometalates, [Dy 6 (ampH) 4 (H 2 O) 23 (ampH 2 )(PW 11 O 39 ) 2 ] (1) and [Dy 9 (CO 3 ) 3 (ampH) 2 (H 2 O) 12 (PW 10 O 37 ) 6 ] 35- (2), are assembled by the same precursor under different pH conditions. The structure of 1 contains an octahedral {Dy 6 (ampH) 4 } core, and a unique windmill-type {Dy 9 (CO 3 ) 3 (ampH) 2 } for 2. Single-molecule magnet behavior is observed for 2 with a thermally activated energy barrier of 56 K and no appreciable quantum tunneling of magnetization under zero field.

A chiral Co(II)-based coordination polymer, [Co 3 (pimda) 2 (H 2 O) 5 ] (1, H 3 pimda = 2-propyl-1H-imidazole-4,5-dicarboxylic acid) with 3D hyperkagomé topology is reported. Upon heating/cooling, the water molecules which are coordinated to a pair of crystallographically symmetric Co(II) ions are removed/recovered discretely in two steps, giving [Co 3 (pimda) 2 (H 2 O) 4 ] (2) and [Co 3 (pimda) 2 (H 2 O) 3 ] (3), which is evidenced by the reversible single-crystal-to-single-crystal (SCSC) structural transformations. As the coordination geometry of the two Co(II) ions changes from octahedron to trigonal bipyramid, obvious color change from pink for 1 to dark violet for 2 and 3 is observed. Further magnetic measurements demonstrate the presence of a solvatomagnetic effect from paramagnets for 1 and 2 to weak ferromagnet for 3. Moreover, as revealed by the variable-temperature crystallographic measurements, the first and second dehydration temperatures could be controlled from 298 K (25 °C) and 383 K (110 °C) sealed in a capillary (high humidity) to 255 K (-18 °C) and 307 K (34 °C) in dry N 2 (low humidity), indicating the strong humidity sensitivity of the structural dynamics.

Magneto-structural correlation studies of mononuclear intermediate S = 3/2 Fe(III) complexes, (PMe 3 ) 2 FeCl 3 (1) and (PMe 2 Ph) 2 FeCl 3 (2), demonstrate the influence of local symmetry on magnetic anisotropy. Symmetric compound 1 is characterized by a zero-field splitting (ZFS) parameter of D = -50(2) cm -1 , leading to the observation of slow magnetic relaxation with an energy barrier of 81 cm -1 along with magnetic hysteresis up to 4 K, whereas symmetrically perturbed compound 2 displays a much reduced ZFS parameter of D = -17(1) cm -1 and energy barrier of U eff = 46 cm -1 .

The dimeric molecule [Dy 2 (acac) 6 (MeOH) 2 (bpe)]·bpe·2MeOH (1, acac = acetylacetonate, bpe = 1,2-bis(4-pyridyl)ethylene) undergoes a solid-state ligand substitution reaction upon heating, leading to the one-dimensional chain [Dy(acac) 3 (bpe)] n (2). This structural transformation takes advantage of the potential coordination of the guest bpe molecules present in 1. In both complexes the Dy(III) ions adopt similar octacoordinated D 4d geometries. However, the different arrangement of the negatively charged and neutral ligands alters the direction of magnetic anisotropy axis and the energy states, thus resulting in largely distinct magnetization dynamics, as revealed by the CASSCF/RASSI calculations.

A bifunctional dysprosium(III) dimer, [Dy 2 (HTPEIP OMe ) 2 (OAc) 4 (NO 3 ) 2 ] (1), comprising an AIE-active (AIE = aggregation-induced emission) ligand of 2-methoxy-6-[[[4-(1,2,2-triphenylvinyl)phenyl]imino]methyl]phenol (HTPEIP OMe ), was successfully synthesized. It not only behaves as a single-molecule magnet (SMM) with an energy barrier of 168(15) K at zero field but also exhibits piezochromism during the pressing-fuming cycle with switchable color, photoluminescence, and magnetic response.

The first spin-crossover cluster helicate [{Fe(II)(μ-bpt)3}2Fe(II)3(μ3-O)][Fe(II)2(μ-Cl)(μ-bpt)(NCS)4(H2O)]·2H2O·C2H5OH [Hbpt = 3,5-bis(pyridin-2-yl)-1,2,4-triazole] was reported, in which one spin-crossover unit and one low-spin triple-stranded [Fe(II)(bpt)3](-) unit wrapped a rare planar [Fe(II)3(μ3-O)](4+) core to form a bis(triple-helical) cation with trigonal-bipyramidal topology. The origin of different magnetic behaviors of two [Fe(II)(bpt)3](-) units could be ascribed to their different intermolecular interactions.

Single-molecule magnets (SMMs) with a large spin reversal barrier have been recognized to exhibit slow magnetic relaxation that can lead to a magnetic hysteresis loop. Synthesis of highly stable SMMs with both large energy barriers and significantly slow relaxation times is challenging. Here, we report two highly stable and neutral Dy(III) classical coordination compounds with pentagonal bipyramidal local geometry that exhibit SMM behavior. Weak intermolecular interactions in the undiluted single crystals are first observed for mononuclear lanthanide SMMs by micro-SQUID measurements. The investigation of magnetic relaxation reveals the thermally activated quantum tunneling of magnetization through the third excited Kramers doublet, owing to the increased axial magnetic anisotropy and weaker transverse magnetic anisotropy. As a result, pronounced magnetic hysteresis loops up to 14 K are observed, and the effective energy barrier (Ueff = 1025 K) for relaxation of magnetization reached a breakthrough among the SMMs.

A stable Dy(III)-dispersed compound with single-molecule magnet behavior, Dy(0.06)Y(0.94)(OH)CO3, was isolated by a general strategy targeted at the doping of paramagnetic Dy(3+) into a diamagnetic 3D inorganic network of Y(OH)CO3. The single-ion origin of slow magnetic relaxation was gradually released as variations of the dysprosium/yttrium ratio and finally gave a relatively large spin-reversal barrier around 200 K and high hysteresis temperature of 8 K. This study opens up new opportunities to investigate the slow magnetic relaxation and magnetostructural correlation by choosing a suitable inorganic architecture with strong axial anisotropy.

Single-molecule magnets (SMMs) that can be trapped in one of the bistable magnetic states separated by an energy barrier are among the most promising candidates for high-density information storage, quantum processing, and spintronics. To date, a considerable series of achievements have been made. However, the presence of fast quantum tunnelling of magnetization (QTM) in most SMMs, especially in single-ion magnets (SIMs), provides a rapid relaxation route and often sets up a limit for the relaxation time. Here, we pursue the pentagonal bipyramidal symmetry to suppress the QTM and present pentagonal bipyramidal Dy(III) SIMs [Dy(Cy3PO)2(H2O)5]Cl3·(Cy3PO)·H2O·EtOH (1) and [Dy(Cy3PO)2(H2O)5]Br3·2(Cy3PO)·2H2O·2EtOH (2), (Cy3PO = tricyclohexyl phosphine oxide). Magnetic characterizations reveal their fascinating SMM properties with high energy barriers as 472(7) K for 1 and 543(2) K for 2, along with a record magnetic hysteresis temperature up to 20 K for 2. These results, combined with the ab initio calculations, offer an illuminating insight into the vast possibility and potential of what the symmetry rules can achieve in molecular magnetism.

Three new two-dimensional (2D) Hofmann-type coordination polymers with general formula [Fe(3-NH2py)2M(CN)4] (3-NH2py = 3-aminopyridine, M = Ni (1), Pd (2), Pt (3)) have been synthesized. Magnetic susceptibility measurements show that they exhibited cooperative spin crossover (SCO) with remarkable hysteretic behaviors. Their hysteresis widths are 25, 37, and 30 K for 1-3, respectively. The single-crystal structure of 1 suggest that the pseudo-octahedral Fe sites are equatorially bridged by [M(CN)4](2-) to form 2D grids and axially coordinated by 3-NH2py ligands. The intermolecular interactions between layers (the offset face-to-face π···π interactions, hydrogen bonds, and weak N(amino)···Ni(II) contacts) together with the covalent bonds bridged by [M(CN)4](2-) units are responsible to the significant cooperativity.

Thanks to the MeCN hydrolysis in situ reaction, a [2 × 2] square grid Dy(III)4 cluster based on a polypyridyl triazolate ligand, [Dy4(OH)2(bpt)4(NO3)4(OAc)2] (1), was separated successfully and characterized through single-crystal X-ray diffraction and SQUID magnetometry. The frequency-dependent signals in the out-of-phase component of the susceptibility associated with slow relaxation of the magnetization confirmed that complex 1 displays single-molecule magnet (SMM) behavior. Two distinct slow magnetic relaxation processes, with effective energy barriers Ueff1 = 93 cm(-1) for fast relaxation and Ueff2 = 143 cm(-1) for slow relaxation observed under a zero direct-current field, are mainly attributed to the origin of single-ion behavior, which can be further acknowledged by the magnetic investigation of a dysprosium-doped yttrium cluster. Besides, it should be noted that complex 1 represents so far the highest energy barrier among the pure Dy(III)4 SMMs.

Two solvent-free two-dimensional (2D) coordination polymers, (2)∞[Fe(ptim)2] (1) and (2)∞[Fe(ptpy)2] (2) (Hptim = 2-(5-(4-(1H-imidazol-1-yl)phenyl)-4H-1,2,4-triazol-3-yl)pyridine; Hptpy = 2-(5-(4-(pyridin-3-yl)phenyl)-4H-1,2,4-triazol-3-yl)pyridine), have been successfully prepared by solvothermal reactions. Their iron atoms are bridged by the corresponding multidentate anionic ligands into dense neutral structures. The magnetic data reveal that complexes 1 and 2 are rare examples exhibiting reversible one-step high-temperature spin crossover behaviors with spin transition temperatures of 419 and 416 K, respectively. Moreover, these structures also display remarkable thermal stability up to 714 K (for 1) and 690 K (for 2), which are confirmed by thermogravimetric and variable-temperature powder X-ray diffraction analyses.

Two new oxalate-bridged Gd(III) coordination polymers, namely, (choline)[Gd(C2O4)(H2O)3Cl]Cl·H2O (1) and [Gd(C2O4)(H2O)3Cl] (2), were first obtained ionothermally by using a deep eutectic solvent (DES). The magnetic studies and heat capacity measurements reveal that the two-dimensional Gd(III)-based coordination polymer of 2 has the higher magnetic density and exhibits a larger cryogenic magnetocaloric effect (MCE) (ΔS(m) = 48 J kg(-1) K(-1) for ΔH = 7 T at 2.2 K).

Three one-dimensional (1D) hetereobimetallic coordination polymers [Fe(II)(L)2(AgCN)2]·Solv (L = bpt(-), 1; L = Mebpt(-), Solv = 1.75EtOH, 2; L = bpzt(-), 3) with in situ generated AgCN species were synthesized by solvothermal reactions of Fe(II) salt, K[Ag(CN)2], and the corresponding ligands [bptH = 3,5-bis(pyridin-2-yl)-1,2,4-triazole, MebptH = 3-(3-methyl-2-pyridyl)-5-(2-pyridyl)-1,2,4-triazole, and bpztH = 3,5-bis(pyrazin-2-yl)-1,2,4-triazole]. They were further characterized by X-ray crystallography, magnetic and photomagnetic measurements, and differential scanning calorimetry. Single-crystal X-ray analyses show that they are isostructural with 1D zigzag chain structures with rhombus {Fe2Ag2} units, in which the substituted bpt(-) ligand connects the Fe(II) ion and AgCN species in a cis bridging mode. Then the zigzag chains are packed into three-dimensional supramolecular structures by π···π interactions. Most importantly, weak Ag···N interactions (2.750 Å at 150 K) between the π-stacked neighboring chains present in complex 3. Magnetic susceptibility measurements exhibit that complex 1 displays characteristic paramagnetic behavior in the temperature range investigated. Complex 2 undergoes a gradual spin-crossover (SCO) with critical temperatures T(1/2)↓ = 232 K and T(1/2)↑ = 235 K, whereas 3 exhibits an abrupt SCO with critical temperatures T(1/2)↓ = 286 K and T(1/2)↑ = 292 K. The magnetostructural relationships suggest that the magnetic behaviors can be modulated from paramagnetic behavior to abrupt and hysteretic SCO near room temperature through adjustment of the electronic substituent effect and intermolecular interactions.

Porous and nonporous 3D heterobimetallic coordination polymers based on the 1,4-di(pyridin-4-yl)benzene ligand (dpb), [Fe(dpb){Ag(CN)2}{Ag2(CN)3}]·nSolv (1·nSolv; nSolv = DMF·EtOH, 2DMF·MeCN) and [Fe(dpb)2{Ag(CN)2}2] (2), have been synthesized by diffusion technique, respectively. Single-crystal X-ray analysis shows that 1·nSolv consists of a 3D self-penetrating network with in-situ-generated [Ag2(CN)3](-) species and displays one of the largest volume values of porosity (299 Å(3) per iron atom) after desolvation for the Hoffman-like porous SCO coordination polymers to date. In contrast, nonporous compound 2 is composed of two independent interpenetrated 3D nets with in-situ-generated [Ag(dpb)(CN)2](-) species. Their significant distinctions of structural architectures lead to dramatically different magnetic properties: 1·nSolv displays two-step guest-effected SCO with hysteresis, whereas 2 presents characteristic paramagnetic behavior.