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With the purpose to develop long chain-conjugated oligopyrrin-like compounds and their metal complexes, and thus achieve tunable near-infrared absorption, a dithienyl-blocked hexapyrrane S2-P6 was synthesized by acid-catalyzed [2+4+2] condensation, followed by oxidation with DDQ to afford dithiaoctapyrrin 1, and its mononuclear metal complexes 1-Cu and 1-Zn were synthesized by treating 1 with Cu(II) and Zn(II) acetates. All the compounds were systematically characterized by NMR/EPR, and HRMS. The crystal structures revealed that 1 adopts a double hook-like conformation. Whereas, both complexes 1-Cu and 1-Zn adopt spiral-hook hybrid conformations, showing smaller interplanar angles between the rings within the spiral part, compared with those in the hook-like counterpart of molecule 1, which is favorable for red-shifting the absorption. As expected, the absorption band edges for complexes 1-Cu and 1-Zn are red-shifted to ca. 1560 nm, compared with that of 1260 nm observed for 1.

Four novel isostructural heterometallic dysprosium–hexacyanometallate frameworks, namely {[Dy4(L)4(H2O)4(CH3OH)4M(CN)6]·Cl·8H2O}n and {[Dy4(L)4(H2O)4(CH3OH)4M(CN)6]·Br·4CH3OH}n (M = Fe for 1 and 3, Co for 2 and 4; H2L = N′-(2-hydroxybenzylidene)picolinohydrazide) have been successfully assembled by a feasible approach employing a superparamagnetic dimeric unit as the building block and hexacyanometallates [M(CN)6]3− as bridges. Within these frameworks, hexacyanometallates serve as 4-way nodes and connect the adjacent dimeric building blocks to form a three-dimensional diamond-like structure with a Schlafli symbol of 6^6. Magnetic measurements indicate the ferromagnetic nature of intradimer Dy3+–Dy3+ interactions, the antiferromagnetic coupling between Dy3+ ions and adjacent [Fe(CN)6]3− units, as well as the dynamic magnetic behaviour under zero dc field with the effective energy barriers of 111(2), 283(8), 108(2), and 280(15) K for 1–4, respectively. Ab initio calculations and in-depth magneto-structural studies demonstrate that the magnetic anisotropy of Dy3+ ions and the intradimer ferromagnetic coupling are positive factors for slowing down the quantum tunnelling of magnetization (QTM), resulting in the highest effective energy barrier and the largest coercive field for 2 among all compounds, while the antiferromagnetic interaction between Dy3+ ions and [Fe(CN)6]3− units can accelerate the QTM and thus shut off the magnetic memory effect of 1 and 3 at low temperature.

Single-molecule magnets (SMMs) are expected to be promising candidates for the applications of high-density information storage materials and quantum information processing. Lanthanide SMMs have attracted considerable interest in recent years due to their excellent performance. It has always been interesting but not straightforward to study the relaxation and blocking mechanisms by embedding 3d ions into 4f SMMs. Here we report a family of air-stable 3d-4f ion-pair compounds, YFe (1), DyCr (2), DyFe (3), DyCo (4), and Dy0.04Y0.96Fe (5), composed of pentagonal bipyramidal (D5h) LnIII cations and transition metallocyanate anions. The ion-pair nature makes the dipole-dipole interactions almost the only component of the magnetic interactions that can be clarified and analytically resolved under proper approximation. Therefore, this family provides an intuitive opportunity to investigate the effects of 3d-4f and 4f-4f magnetic interactions on the behavior of site-resolved 4f SMMs. Dynamic magnetic measurements of 1 under a 4 kOe external field reveal slow magnetic relaxation originating from the isolated [FeIII]LS (S = 1/2) ions. Under zero dc field, compounds 2-5 show similar magnetic relaxation processes coming from the separated pentagonal bipyramidal (D5h) DyIII ions with high Orbach barriers of 592(5), 596(4), 595(3), and 606(4) K, respectively. Comparatively, both compounds 3 and 5 exhibit two distinct relaxation processes, respectively from the [FeIII]LS and DyIII [Ueff = 596(4) K for 3 and 610(7) K for 5] ions, under a 4 kOe dc field. The dipolar interactions between the neighboring TMIII (TM = transition metal, CrIII or [FeIII]LS) and DyIII ions were revealed to have little effect on the thermal relaxation in compounds 2, 3, and 5, or the coexistence of the two separate relaxation processes in compounds 3 and 5 under a 4 kOe dc field, but they significantly affect the quantum tunneling of magnetization and the magnetic hysteresis behavior of 2 and 3 at low temperatures compared to those of 4.

A family of cyano-bridged 3d-4f 1D chain compounds, {RE[TM(CN)6(2-PNO)5]}·(H2O)4 {RE = YIII, TM = [FeIII]LS (1); RE = DyIII, TM = CoIII (3); RE = ErIII, TM = [FeIII]LS (4), CoIII (5); 2-PNO = 2-picoline-N-oxide} and {RE[TM(CN)6(2-PNO)5]} {RE = DyIII, TM = [FeIII]LS (2)}, were synthesized and characterized. Single-crystal X-ray diffraction studies reveal that compounds 1 and 3-5 are isostructural, while compound 2 has a similar 1D chain structure with a different chain to chain arrangement. An axially-elongated pentagonal bipyramidal (D5h) coordination geometry is formed with five 2-PNO ligands in the equatorial plane and two [TM(CN)6]3- on the apical sites around the rare earth ions in these compounds. A comparison of the magnetic relaxation behaviour in detail reveals that it is more favorable for the Er (4 and 5) than the Dy analogues (2 and 3) to exhibit SIM properties in this axially-elongated D5h coordination environment. Under zero dc field, ac susceptibility measurements show that the Dy analogues have no magnetic relaxation behaviour, while the Er analogues exhibit frequency dependence despite the strong QTM effect. Under a 1 kOe dc field, the Er analogues generally show 1-2 orders of magnitude longer relaxation time at each selected temperature and a higher relaxation energy barrier than the Dy analogues. And the RECo compounds (3 and 5) show a more suppressed QTM effect than the corresponding REFe (2 and 4) compounds, which may be ascribed to the elimination of the fluctuation field from the neighbouring [FeIII]LS ions. The ab initio calculations indicate the misplacement between the orientation of the main magnetic axis and the structural axis in the Dy analogues, and the relative consistency in the Er analogues, which should be the source of the Er analogues showing better SIM properties than the Dy analogues.

To study the effect of a stable radical on the photophysical properties of a phosphorescent Pt(II) coordination framework and the intramolecular magnetic interaction between radical ligands in the N^N Pt(II) bisacetylide complexes, we prepared a series of N^N Pt(II) bis(acetylide) complexes with oxoverdazyl radical acetylide ligands. The linker between the Pt(II) center and the spin carrier was systematically varied, to probe the effect on the sign and magnitude of the spin exchange interactions between the radical ligands and photophysical properties. The complexes were studied with steady-state and femtosecond/nanosecond transient absorption spectroscopy, continuous-wave electron paramagnetic resonance (EPR) spectroscopy, and density functional theory (DFT) computations. The transient absorption spectral studies show that the doublet excited state of the radicals are short-lived (τ

We investigate a family of dinuclear dysprosium metallocene single-molecule magnets (SMMs) bridged by methyl and halogen groups [Cp'2 Dy(μ-X)]2 (Cp'=cyclopentadienyltrimethylsilane anion; 1: X=CH3- ; 2: X=Cl- ; 3: X=Br- ; 4: X=I- ). For the first time, the magnetic easy axes of dysprosium metallocene SMMs are experimentally determined, confirming that the orientation of them are perpendicular to the equatorial plane which is made up of dysprosium and bridging atoms. The orientation of the magnetic easy axis for 1 deviates from the normal direction (by 10.3°) due to the stronger equatorial interactions between DyIII and methyl groups. Moreover, its magnetic axes show a temperature-dependent shifting, which is caused by the competition between exchange interactions and Zeeman interactions. Studies of fluorescence and specific heat as well as ab initio calculations reveal the significant influences of the bridging ligands on their low-lying exchange-based energy levels and, consequently, low-temperature magnetic properties.

A novel three-dimensional porous dysprosium coordination polymer {[Dy2L2(bpdo)2(H2O)(CH3OH)]·2ClO4·2CH3CN}n (1) has been successfully assembled by combining a superparamagnetic building block of [DyLCl(CH3OH)]2 with the organic ligand 4,4′-bipyridine-N,N′-dioxide (bpdo) (H2L = N′-(2-hydroxybenzylidene)picolinohydrazide). Interestingly, upon the release and/or absorption of different solvent molecules, 1 undergoes reversible single-crystal-to-single-crystal (SCSC) transitions, resulting in the formation of another layer compound of {[DyL(bpdo)(H2O)]·ClO4·2H2O}n (2). This structural transformation involves the breaking and reforming of coordination bonds and leads to significant changes in the relaxation behaviour expected for these coordination polymers, as evidenced by the increase in effective energy barriers from 133 K (1) to 264 K (2) and the slowdown of quantum tunnelling at low temperature. The theoretical calculations indicate that the distinct relaxation behaviours arise mainly from the variation in the coordination geometry around the dysprosium ions. Our work shows that guest molecules can reversibly induce remarkable structural changes in a porous dysprosium coordination polymer and significantly affect its dynamic properties.

Enhancing the exchange interaction between magnetic ions is a long-term target in molecular magnetism. Endohedral metallofullerenes (EMFs) provide a possibility for achieving such a goal by imprisoning multiple magnetic centers inside the confined inner space of a fullerene cage. Here, we report a new member of dimetallic azafullerene Dy2@C79N via crystallographic determination for the first time. Magnetic studies indicate that the strong ferromagnetic coupling between lanthanide ions and unpaired electrons enables Dy2@C79N to be a favorable SMM with large energy barrier of U = 669 K and observable hysteresis loops below 24 K.

New Ln-metal–organic frameworks (Ln-MOFs), {[Ln(2,7-NDS)(IP)(OH)(H2O)2]·mH2O}n [Ln = Sm 1, Eu 2, Gd 3, Tb 4, Dy 5, m = 0.5–0; 2,7-NDS = 2,7-naphthalenedisulfonate, and IP = 1H-imidazo[4,5-f][1,10]-...

For the purpose of further exploring the effect of nonperipherally attached substituents on single-ion magnet (SIMs) performance, tetrasubstituted bis[1,8,15,22-tetrakis(3-pentyloxy)phthalocyaninato]terbium double-deckers, in both the reduced form TbH[Pc(α-OC5H11)4]2 (1) and the neutral form Tb[Pc(α-OC5H11)4]2 (2), were prepared. Single-crystal X-ray diffraction analysis for 2 unambiguously demonstrates the pinwheellike molecular structure with C4 symmetry. Magnetic investigations of the two bis(phthalocyaninato)terbium double-deckers reveal their characteristic SIM nature. 2 exhibits SIM performance superior to that of 1, as revealed by the larger energy barrier of 466 K for the former species and 431 K for the latter species due to the presence of organic radical–f (radical–Tb) interactions. The enhanced SIM performance of 2 in comparison to 1 actually stems from the presence of radical–f interactions and an enhanced ligand field strength. The latter positive factor is indicated by the electrostatic pot...

Two dysprosium complexes bearing unsupported Dy–Ge/Sn metal–metal bonds are reported here, wherein the Dy–Ge and Dy–Sn bonds both contain relatively large covalency. The complexes exhibit slow relaxation of magnetization at zero field with energy barriers of 485 and 620 K, respectively, and the blocking temperature of 6 K.

A novel superparamagnetic dysprosium chain complex, namely, [Dy(L)Cl(CH3OH)]n (1) (H2L = N′-(5-bromo-2-hydroxybenzylidene)pyrazine-N-oxide-carbohydrazide), has been successfully synthesized by the extension of dinuclear units through chloride bridges. Magnetic and theoretical studies indicate that dipolar magnetic interactions induced by the chloride bridges are helpful for the magnetic relaxation process to pass through the second-excited state of dysprosium ions, resulting in the higher energy barrier for 1.

While assembling superparamagnetic units in a controlled manner is crucial for future applications of molecular nanomagnets, optimizing their magnetic properties while achieving directional assembly of these units still remains a formidable challenge. Herein, we demonstrate how the assembly of two dysprosium chain complexes, namely, [Dy2(L)2Cl2(CH3OH)3]n·nCH3OH (1) and [Dy(L)Cl(DMF)]n (2) (H2L = N‘-(5-bromo-2-hydroxybenzylidene)pyrazine-N-oxide-carbohydrazide), can be successfully manipulated using an appropriate bridging ligand design. Both complexes contain similar dimeric units bridged by two alkoxido oxygens from an L2− ligand, but extended by its pyrazine-N-oxide group exhibiting two distinct coordination modes, namely, single and double pyrazine-N-oxide bridges, respectively. Magnetic studies reveal that both complexes display typical slow magnetic relaxation under zero direct-current field; however, the anisotropy barrier and the coercive field at 2 K for complex 2 are twice as much as that of 1. A further theoretical study indicates that switching the coordination mode from a single pyrazine-N-oxide bridge to double bridges can enhance both the magnetic anisotropy of dysprosium ions and magnetic coupling within the dimeric cores. The synergistic effect between the magnetic anisotropy of dysprosium ions and magnetic interactions among them directly contributes to the overall better performance of complex 2.

Enhancing the exchange interaction between magnetic ions is a long-term target in molecular magnetism. Endohedral metallofullerenes (EMFs) provide a possibility for achieving such a goal by imprisoning multiple magnetic centers inside the confined inner space of a fullerene cage. Here, we report a new member of dimetallic azafullerene Dy2@C79N via crystallographic determination for the first time. Magnetic studies indicate that the strong ferromagnetic coupling between lanthanide ions and unpaired electrons enables Dy2@C79N to be a favorable SMM with large energy barrier of U = 669 K and observable hysteresis loops below 24 K.

A class of cyano-bridged 3d-4f zig-zag chain compounds, {RE[TM(CN)6] (PNO)2(H2O)4}·(H2O) {RE = YIII, TM = [FeIII]LS (1); RE = DyIII, TM = [FeIII]LS (2), CoIII (3)}, have been synthesized and characterized by single-crystal X-ray diffraction. The rare earth ions in these compounds are situated in a slightly distorted triangular dodecahedral (D2d) coordination environment. The magnetic properties of compounds 1-3 have been comparatively studied in detail. Under a zero dc field, the temperature dependence of ac susceptibility measurements for YFe (1) indicates the absence of magnetic relaxation stemming from the single anisotropic [FeIII]LS ion. The dysprosium analogue DyFe (2) shows only magnetic relaxation behavior with a prominent QTM effect, while DyCo (3) exhibits SIM properties not completely covered by QTM, with an extracted energy barrier of 73 K under a zero dc field. The ab initio calculations indicate that both compounds 2 and 3 are SMMs with well-behaved magnetic relaxation properties primarily from the individual DyIII ion. Therefore, the different magnetic behaviors exhibited by compound 2 compared to 3 may be ascribed to the stronger QTM effect caused by the extra weak interaction of [FeIII]LS ions in 2 as a fluctuating transverse field around the DyIII ion. The QTM effect for both 2 and 3 is suppressed under an applied dc field with an effective energy barrier of 134 and 150 K, respectively. Compared with compound 2, the higher extracted Ueff/kB and χ''(T) peak temperature for 3 should be further attributed to its slightly higher single-ion axiality as calculated and the elimination of the transverse field from the [FeIII]LS ion.

The non-peripherally substituted 1,4,8,11,15,18,22,25-octa(butoxy)-phthalocyanine-involved unsymmetrical heteroleptic bis(phthalocyaninato) terbium double-decker, Tb(Pc){H[Pc(α-OC4 H9 )8 ]} (Pc=unsubstituted phthalocyanine) (1), was revealed to exhibit typical single ion magnet (SIM) behavior with effective energy barrier, 180 K (125 cm-1 ), and blocking temperature, 2 K, due to the severe deviation of the terbium coordination polyhedron from square-antiprismatic geometry. Fabrication of this double-decker compound into the novel tetrakis(phthalocyaninato) terbium pseudo-quadruple-decker Na2 {Tb(Pc)[Pc(α-OC4 H9 )8 ]}2 (2) single molecule magnet (SMM) not only optimizes the coordination polyhedron of terbium ion towards the square-antiprismatic geometry and intensifies the coordination field strength, but more importantly significantly enhances the molecular magnetic anisotropy in the unsymmetrical bis(phthalocyaninato) double-decker unit, along with the change of the counter cation from H+ of 1 to Na+ of 2, leading to an significantly enhanced magnetic behavior with spin-reversal energy barrier, 528 K (367 cm-1 ), and blocking temperature, 25 K. The present result is surely helpful towards developing novel tetrapyrrole lanthanide SMMs through rational design and self-assembly from bis(tetrapyrrole) lanthanide single ion magnet (SIM) building block.

For the purpose of engineering magnetic anisotropy, chiral binaphthyl substituents with slight electron-withdrawing ability and dibutylamino substituents with intense electron-donating nature are incoporated onto the periphery of each phthalocyanine ligand in the bis(phthalocyaninato) terbium double-decker compound, resulting in the chiral heteroleptic bis(phthalocyaninato) terbium complex (R)/(S)-[Pc(OBNP)4]Tb{Pc[N(C4H9)2]8} (R/S-1) {Pc(OBNP)4 = {tetrakis(dinaphtho[1,2-e:1′,2′-g]-1,4-dioxocine)[2,3-b;2′,3′-k;2′′,3′′-t;2′′′,3′′′-c′]phthalocyanine}; Pc[N(C4H9)2]8 = [2,3,9,10,16,17,23,24-octakis(dibutylamino)phthalocyanine]}. Magnetic studies reveal the typical single-ion magnet (SIM) nature of this chiral bis(phthalocyaninato) terbium double-decker with spin reversal energy barrier of 638 K. A butterfly-shaped magnetic hysteresis loop was observed at even 25 K for R-1 under the sweep rate of 500 Oe s−1. The performance of this SIM is well rationalized on the basis of theoretical analysis of the electrostatic potential according to calculations using the density functional theory method.

A new three-dimensional porous lanthanide coordination polymer {[Dy(L)(μ2-bpdo)0.5(μ4-bpdo)0.5(CH3OH)]·ClO4·3CH3OH}n (2) featuring slow magnetic relaxation has been successfully assembled by reacting a superparamagnetic chain complex{[Dy(HL)(H2O)2(CH3OH)2]·2Cl·CH3OH}n (1) with an organic bridging ligand, namely, 4,4′-bipyridine-N,N′-dioxide (bpdo) (H2L = N′-(2-hydroxybenzylidene)-picolinohydrazide). Compared with 1, complex 2 has a higher magnetic anisotropy barrier, which arises from the variation of the ligand field around dysprosium ions and/or the existence of magnetic coupling between them induced by the bpdo ligand, leading to a thermal magnetic relaxation process through the second-excited doublet. Interestingly, complex 2 can undergo a reversible single-crystal-to-single-crystal conversion accompanying the desorption and adsorption of methanol molecules. The de-solvated phase, {[Dy(L)(μ2-bpdo)0.5(μ4-bpdo)0.5(CH3OH)]·ClO4}n (3), exhibits a slow magnetic relaxation process through the first-excited doublet, presenting the first example of reversible adjustment on the magnetic relaxation pathway regulated by guest molecules. This exciting finding offers a new perspective for enhancing the magnetic relaxation barrier.

A new centrosymmetric tetranuclear aggregate [Dy4(L)2(OAc)8(CH3OH)2] (1) was assembled using a unique symmetrical Schiff base ligand 1,5-bis(salicylidene)-carbohydrazide (H2L). Magnetic studies reveal ferromagnetic interactions between dysprosium ions and two obvious relaxation processes under zero dc field with effective energy barriers Ueff of 38 K and 223 K, the highest among the reported tetranuclear dysprosium molecular nanomagnets. To obtain further evidence on the origination of the slow magnetic relaxation, a diamagnetic yttrium analogue [Y4(L)2(OAc)8(CH3OH)2] (2) and a diluted sample [(Dy0.06Y0.94)4(L)2(OAc)8(CH3OH)2] (3) were synthesized. Further magnetic studies on the diluted sample combined with theoretical calculations indicate that the two-step magnetic relaxation processes in complex 1 originate from the single-ion magnetic behaviors of dysprosium ions with different coordination environments.

Chiral binaphthyl substituents were incorporated onto the phthalocyanine periphery in both homoleptic and heteroleptic bis(phthalocyaninato) terbium single-ion magnets, which exhibit blocking temperatures as high as 15 K and 28 K, respectively, providing an alternative method towards enhancing the magnetic behavior.

An approximately equatorial three-coordinated dysprosium(iii) complex DyL2[N(SiMe3)2] (L = bis(2-(2,5-dimethyl-1H-pyrrol-1-yl)ethyl)amine) with an additional neutral auxiliary pyrrole ligand was synthesised and structurally characterized. The magnetic property measurement shows that it is an equatorial charge distributed field-induced single-molecule magnet. Ab initio calculations reveal that the neutral pyrrole ligand plays an important role in stabilizing the ground doublet and thus enhancing the magnetic anisotropy.

Bulky and strong electron-donating dibutylamino groups were incorporated onto the peripheral positions of one of the two phthalocyanine ligands in the bis(phthalocyaninato) terbium complex, resulting in the isolation of heteroleptic double-decker (Pc)Tb{Pc[N(C4H9)2]8} {Pc = phthalocyaninate; Pc[N(C4H9)2]8 = 2,3,9,10,16,17,23,24-octakis(dibutylamino)phthalocyaninate} with the nature of an unsymmetrical molecular structure, a square-antiprismatic coordination geometry, an intensified coordination field strength, and the presence of organic radical-f interaction. As a total result of all these factors, this sandwich-type tetrapyrrole lanthanide single-ion magnet (SIM) exhibits an overall enhanced magnetic performance including a high blocking temperature (TB) of 30 K and large effective spin-reversal energy barrier of Ueff = 939 K, rendering it the best sandwich-type tetrapyrrole lanthanide SIM reported thus far.

Linear tetrapyrrole is the core structure of light-sensitive native cofactors such as phycocyanobilin, phytochromobilin and bile pigments, which attracts increasing attention in biomimetic chemistry, photochemistry and coordination chemistry. To decipher the relationship between structures and functions, in this work, we firstly reported the synthesis, isolation and characterization of three bilindione isomers (ZZZ, syn, syn, syn 1, EZE, syn, syn, anti 2 and EZE, anti, syn, anti 3) bearing meso-pentafluorophenyl groups. The structures were confirmed by X-ray diffraction and 2-D NMR spectroscopes. More importantly, the interconversion between three isomers under heating and light irradiation was investigated, and isomer 3 was found to be transformed to 1 and 2 more easily, which is in line with the results of DFT calculation. This work provides important insights for understanding the relationship between structures and functions and would be important to further construct metal complexes based on linear tetrapyrrole ligands, which are complementary to well-studied the cyclic analogs such as porphyrin and corroles.

“Configurational isomerism” is an important approach found in naturally occurring chlorophylls to modulate light harvesting function without significant structural changes; however, this feature has been seldom applied in design of antenna ligands for lanthanide (Ln) sensitization. In this work, we introduced a bioinspired approach by orientation of β-dilactone moieties on porphyrinates, namely cis-/trans-porphodilactones, to modulate the energy transfer process from the lowest triplet excited state of the ligand (T1) to the emitting level of ytterbium(III) (2F5/2, Yb*). Interestingly, near-infrared (NIR) emission of Yb(III) could be switched “on” by the cis-porphodilactone ligand, while the trans-isomer renders Yb(III) emission “off” and the ratio of quantum yields is ∼8. Analysis of the structure–photophysical properties relationship suggests that the significant emission difference is correlated to the energy gaps between T1 and Yb* (1152 cm–1 in the cis- vs −25 cm–1 in the trans-isomer). More interest...

Strong electron-donating dialkylamino groups were incoporated onto the phthalocyanine ligand in bis(phthalocyaninato) rare earth complexes for the first time to investigate their effects on the spectroscopic properties, electrochemistry, and electronic structure. The bis[2,3,9,10,16,17,23,24-octakis(dibutylamino)phthalocyaninate] rare earth complexes M{Pc[N(C4H9)2]8}2 {Pc[N(C4H9)2]8 = 2,3,9,10,16,17,23,24-octakis(dibutylamino)phthalocyanine, M = Y, Tb} (1, 2) were isolated from the condensation reaction of the corresponding metal free ligand in a refluxing mixture of n-octanol/1,2,4-trichrolobenzene (TCB) (1 : 5) in the presence of M(acac)3·nH2O (M = Y, Tb) in relatively good yields, with their sandwich double-decker nature revealed on the basis of their mass, 1H NMR, electronic absorption, IR, and EPR spectroscopic results in addition to elemental analysis. Their electrochemistry was investigated by cyclic voltammetry (CV). In particular, magnetic studies reveal the typical slow relaxation of the terbium double-decker, indicating its typical single-ion magnet (SIM) nature with a blocking temperature of 25 K and a spin reversal energy barrier of 752 ± 8 K, representing the sole example of sandwich-type tetrapyrrole lanthanide-based SMMs reported thus far with a blocking temperature over 20 K. Theoretical calculations disclose the effect of the bulky and strong electron-donating peripheral dialkylamino groups, which create a square-antiprismatic coordination geometry and intensified coordination field strength for the central terbium ion, resulting in the excellent magnetic performance of this terbium double-decker SIM.

Two novel dysprosium complexes, namely, [Dy2L2(NO3)2(DMF)2]·2DMF (1) and [Dy4L4(OAc)4(DMF)2] (2), have been successfully synthesized by reacting a new pyridine-N-oxide-containing organic ligand N′-(8-hydroxyquinoline-2-carboxaldehyde)pyridine-N-oxide-carbohydrazide (H2L) with different dysprosium salts. The single-crystal X-ray diffraction study revealed that they show either one-dimensional (1D) or tetranuclear structure that is governed by the coordination anion used during the reaction. Within the 1D structure of 1, the nine-coordinated Dy3+ ions are bridged by two phenol oxygen atoms from the 8-hydroxyquinoline group to form Dy2 dimers and these dimers are further connected by pyridine-N-oxide groups. While in 2, the two octa-coordinated Dy3+ ions are bonded together by both phenol oxygen and acetate bridges to produce the Dy2 units and two adjacent Dy2 units are further linked by pyridine-N-oxide groups, resulting in a tetranuclear structure. Magnetic studies indicate that the anisotropic Dy3+ ions in 1 and 2 are ferromagnetically and anti-ferromagnetically coupled, respectively. The alternating current (ac) susceptibility measurements revealed slow magnetic relaxation with effective energy barriers of Ueff = 18.0 K under zero dc field in complex 1. However, under zero dc field, the ac data for 2 show negligible out-of-phase signals, excluding the existence of slow magnetic relaxation. Theoretical studies indicate that the different magnetic relaxation behaviors of both complexes were attributed to the different coordination environments around Dy3+ ions and the distinct magnetic coupling between them.

Several novel flavonoids nitrogen mustard derivatives were synthesized and evaluated for antiproliferative activity against seven human cancer cell lines (HeLa, A549, HepG2, MCF7, SH-SY5Y, PC-3, DU145) by the MTT assay in vitro. The resulting IC50 showed that most compounds exhibited better inhibitory activity against seven cell lines. IC50 values of some compounds were lower than well-known melphalan. In particular, compound 8b was the most promising compound which inhibited HeLa cells with IC50 value of 1.43 μM. It showed excellent antitumor activity against these seven cell lines. Besides, it could arrest cell cycle of HeLa in G2/M phase and induce cell apoptosis. The loss of mitochondrial membrane potential may be an apoptotic mediating factor.

New Ln-metal-organic frameworks (Ln-MOFs), {[Ln(2,7-NDS)(IP)(OH)(H

Two dysprosium complexes bearing unsupported Dy-Ge/Sn metal-metal bonds are reported here, wherein the Dy-Ge and Dy-Sn bonds both contain relatively large covalency. The complexes exhibit slow relaxation of magnetization at zero field with energy barriers of 485 and 620 K, respectively, and the blocking temperature of 6 K.

The spin state transition from low spin to high spin upon substrate addition is one of the key steps in cytochrome P450 catalysis. External perturbations such as pH and hydrogen bonding can also trigger the spin state transition of hemes through deprotonated histidine (e.g. Cytochrome c). In this work, we report the isolated 2-methylimidazole Cobalt(II) [Co(TPP)(2-MeHIm)] and [Co(TTP)(2-MeHIm)], and the corresponding 2-methylimidazolate derivatives where the N−H proton of axial 2-MeHIm is removed. Interestingly, various spectroscopies including EPR and XAFS determine a high-spin state (S = 3/2) for the imidazolate derivatives, in contrast to the low-spin state (S = 1/2) of all known imidazole analogs. DFT assisted stereoelectronic investigations are applied to understand the metal-ligand interactions, which suggest that the dramatically displaced metal center allowing a promotion eg(dπ) → b1g(\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$d_{x^2 - y^2}$$\end{document}dx2-y2) is crucial for the occurrence of the spin state transition., Studying the electronic structures and spin transitions of synthetic heme analogs is crucial to advancing our understanding of heme enzyme mechanisms. Here the authors show that a Co(II) porphyrin complex undergoes an unexpected spin state transition upon deprotonation of its axial imidazole ligand.

A novel two-dimensional dysprosium(III) complex, [Dy(L)(CH3COO)]·0.5DMF·H2O·2CH3OH (1), has been successfully synthesized from a new pyridine-N-oxide (PNO)-containing ligand, namely, N'-(2-hydroxy-3-methoxybenzylidene)pyridine-N-oxidecarbohydrazide (H2L). Single-crystal X-ray diffraction studies reveal that complex 1 is composed of a dinuclear dysprosium subunit, which is further extended by the PNO part of the ligand to form a two-dimensional layer. Magnetic studies indicate that complex 1 shows well-defined temperature- and frequency-dependent signals under a zero direct-current (dc) field, typical of slow magnetic relaxation with an effective energy barrier Ueff of 33.6 K under a zero dc field. Interestingly, powder X-ray diffraction and thermogravimetric analysis reveal that compound 1 undergoes a reversible phase transition that is induced by the desorption and absorption of methanol and water molecules. Moreover, the desolvated sample [Dy(L)(CH3COO)]·0.5DMF (1a) also exhibits slow magnetic relaxation but with a higher anisotropic barrier of 42.0 K, indicating the tuning effect of solvent molecules on slow magnetic relaxation.

Synthesis of two trans-dihydroxy platinum(IV) porphyrins (TPP, tetraphenylporphyrin and F[Formula: see text]TPP, tetrakispentafluorophenylporphyrin) by dimethyl dioxirane (DMD) oxidation of their Pt[Formula: see text] porphyrin precursors have been described. The oxidation state of Pt cation in such complexes was assessed by X-ray photoelectron spectroscopy and shown to be [Formula: see text]4. More importantly, proton was found to promote the formation and stabilization of the trans-dihydroxy platinum(IV) porphyrins, as revealed by UV-vis spectroscopic results and single crystal structures. In addition, these trans-dihydroxy Pt[Formula: see text] porphyrins were much easier to be reduced than their Pt(II) counterparts and capable to transfer oxygen atom to triphenylphosphine and thioanisol, which is important for further application of Pt(IV) complexes in catalytic reactions.

Two novel luminescent three-dimensional coordination polymers [Eu2(tpphz)(oba)3]·nH2O (n = 5.5 for 1, n = 3.5 for 2; H2oba = 4,4′-dicarboxydiphenyl ether) have been hydrothermally synthesized by in situ generation of tetrapyrido[3,2-a:2′,3′-c:3′′,2′′-h:2′′′,3′′′-j]phenazine (tpphz) ligand from 2-(4-pyridine)-imidazo-[4,5-f]1,10-phenanthroline precursor. Both complexes are rare examples of eight-connected self-penetrating networks. The porous nature of the structures is further supported by gas adsorption measurements.

In this work, five novel lanthanide(III) coordination polymers derived from 2-phenylpyrimidine-4-carboxylic acid (Hppmc), namely, [Ln(ppmc)3(H2O)2]·2H2O [Ln = Eu (1), Tb (2)] and [Ln(ppmc)3(H2O)2] [Ln = Eu (3), Gd (4), Tb (5)] were successfully synthesized by a facile solution method and characterized by single-crystal X-ray diffraction, power X-ray diffraction (PXRD), infrared (IR) spectroscopy, elemental analysis, and thermogravimetric analysis (TGA). It was found that subtly different reaction conditions result in disparate structural characteristics. For example, by combining Hppmc with lanthanide(III) ions at room temperature, compounds 1 and 2 featuring a carboxylate-bridging chain structure, in which the carboxylates adopt both chelating and bridging modes, are isolated. However, the reaction at 35 °C generates three isostructural compounds 3–5 with a distinct chain structure, in which the lanthanide ions are connected by carboxylates via syn–syn and syn–anti modes. Photoluminescent studies of the Eu3+ and Tb3+ complexes reveal that the Hppmc ligand is a better sensitizer for Tb3+ ion than for Eu3+ ion. The investigation of the relationship between the crystal structures and the photoluminescence properties indicate that the coordination environments of lanthanide ions and the arrangement of the ligands are the dominating factors that affect the luminescence behaviors of the solid samples.

A new 1D Dy3+ complex based on β-diketone, namely, [Dy(L)3(H2O)]·0.5CH3OH·0.5H2O (1) (HL = 1-phenyl-3-(4′-pyridyl-N-oxide)-propane-1,3-dione) has been designed and synthesized by the combination of β-diketone and pyridine-N-oxide group. The magnetic study indicates the compound's slow magnetic relaxation originating from the single-ion behavior of Dy3+ with strong anisotropy, which is further supported by theoretical calculations.

A chain complex [Dy(L)(NO3)2CH3OH]n (1) and a dinuclear compound [Dy2(L)2(NO3)4(CH3OH)2]·2CH3OH (2) were synthesized by the assembly of a novel pyridine-N-oxide-containing ligand with dysprosium nitrate under different reaction temperatures, where two coordinating nitrates are located in para or ortho position with respect to each other around dysprosium ions. Magnetic studies indicate that the chain complex with two para-coordinating nitrates shows fast quantum tunnelling of the magnetization under zero direct-current field, while the dinuclear complex with two ortho-coordinating nitrates exhibits a thermal-activated process with an effective energy barrier of 51 K. Theoretical and magneto-structural correlation studies indicate that position change of coordinating nitrates can significantly modulate the crystal field around dysprosium ion and further lead to their different relaxation behaviors.

Two new chiral six-coordinate lanthanide complexes (1 for Dy and 2 for Tb) have been synthesized using the achiral flexible ligand H2L (2,2'-[1,2-ethanediylbis[(methylimino)methylene]]bis[4,5-dimethylphenol]). Both complexes crystallize in the chiral P1 group space, and the enantiomers [Zn(L)Cl]3Dy·MeOH·0.5H2O (Λ-1), [Zn(L)Cl]3Dy·1.5H2O (Δ-1), [Zn(L)Cl]3Tb·1.5H2O (Λ-2) and [Zn(L)Cl]3Tb·H2O (Δ-2) are isolated in the reaction. Three [Zn(L)Cl]- anions coordinate to the central lanthanide ion using two phenoxo oxygen atoms of L2-, and the lanthanide ion has the coordination geometry of D3. Complex 1 exhibits a field-induced slow magnetization relaxation, which is typical of a single-ion magnet (SIM). Ab initio calculations on complex 1 and studies on magneto-structural correlationship of six-coordinate Dy(iii) SIMs indicate that the small energy barrier of complex 1 might be related to the absence of a unique anisotropic axis for the regular octahedral coordination configuration of Dy(iii) and the high quantum tunneling gap between the ground states (mJ = ±15/2). Complex 2 displays green photofluorescence and triboluminescence.

In the original version of this Article, the four structural depictions of orbital distributions were inadvertently omitted from Figure 5. This has now been corrected in both the HTML and PDF versions of the Article.

By combining a halogen bonding donor of 1,4-diiodotetrafluorobenzene (1,4-DITFB) or 1,2-diiodotetrafluorobenzene (1,2-DITFB) with 4-benzoyloxy-2,2,6,6-tetramethyl-piperidine-1-oxy free radical (BTEMPO, 1), two novel cocrystals, BTEMPO·1,4-DITFB (2) and BTEMPO·2(1,2-DITFB) (3), featuring a one-dimensional (1D) zigzag chain and a cyclic tetrameric structure, respectively, were constructed via halogen bonding. Furthermore, by tuning the halogen bonding between BTEMPO and halogen bonding donors, the packing modes of organic free radicals in both 2 and 3 are successfully modulated to result in side-by-side 1D mode in 2 and head-to-head dimer manner in 3. Magnetic studies reveal that in all compounds the organic radicals are antiferromagnetically coupled; however, the magnetic coupling in 2 and 3 is stronger than that in 1, indicating the modulating effect of halogen bonding on magnetic properties that are further confirmed by quantum chemistry calculations.

A dinuclear complex [DyLClCH3OH)]2 (1) and a one-dimensional compound [DyL(HCOO)(CH3OH)]n (2) have been synthesized using an organic ligand of N′-(2-hydroxybenzylidene)picolinohydrazide (H2L). Complex 1 exhibits a symmetric dinuclear structure, in which the Dy3+ centers reside in a pentagonal-bipyramidal coordination environment. In 2, the dinuclear units of 1 are strung into chains by formate anions, in which Dy3+ ions are situated in an octa-coordinated, hula-hoop-like coordination geometry. Magnetic studies reveal that ferromagnetic coupling is found between Dy3+ ions in both compounds. Complexes 1 and 2 exhibit slow magnetic relaxation under zero dc field with effective energy barriers of 88.4 and 175.8 K, respectively. Magnetic study combined with ab initio calculations indicates that the better performance of 2 is related to the unique molecular geometry and relatively stronger Dy3+–Dy3+ magnetic interaction within and/or between the dimer units.

A tricoordinated gold(I) chloride complex, tBuXantphosAuCl, supported by a sterically bulky 9,9-dimethyl-4,5-bis(di-tert-butylphosphino)xanthene ligand (tBuXantphos) was synthesized. This complex features a remarkably longer Au-Cl bond length [2.632(1) Å] than bicoordinated linear gold complexes (2.27-2.30 Å) and tricoordinated XantphosAuCl [2.462(1) Å]. Single-crystal X-ray diffraction analysis of a cocrystal of tBuXantphosAuCl and pentafluoronitrobenzene (PFNB) and UV-vis spectroscopic titration experiments revealed the existence of an anion-π interaction between the Cl anion ligand and PFNB. Stoichiometric reaction between PFNB and tBuXantphosAuOtBu, after replacement of Cl by a more nucleophilic tBuO anion ligand, showed higher reactivity and para selectivity in the transformation of C-F to C-OtBu bond, distinctively different from that when only KOtBu was used (ortho selectivity) under the identical condition. Mechanistic studies including density functional theory calculations suggested a gold-mediated nucleophilic ligand attack of the C-F bond pathway via an SNAr process. On the basis of these results, using trimethylsilyl derivatives TMS-X (X = OMe, SEt, NEt2) as the nucleophilic ligand source and the fluorine acceptor, catalytic transformation of the C-F bond of aromatic substrates to the C-X (X = O, S, N) bond was achieved with tBuXantphosAuCl as the catalyst (up to 20 turnover numbers).

Molecular spintronics, which combines spintronics and molecular electronics, is an emerging field of research. Low-dimensional molecular magnets such as single molecule magnets (SMMs) and single chain magnets (SCMs) can potentially be used as spin carriers in spintronic devices, and hence have attracted considerable interest. By using different bridging ligands, a number of L.-M. Zheng (*) • M. Ren School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, People’s Republic of China e-mail: lmzheng@nju.edu.cn J. Tang State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, People’s Republic of China e-mail: tang@ciac.ac.cn H.-L. Sun Department of Chemistry, Beijing Normal University, Beijing, People’s Republic of China # Springer Science+Business Media Dordrecht 2016 Y. Xu et al. (eds.), Handbook of Spintronics, DOI 10.1007/978-94-007-6892-5_26 617 compounds showing SMM or SCM behaviors have been reported. This review article covers the following aspects: (1) SMMs based on the oxo-bridged transition metal clusters with the main focus on the Mn-O and Fe-O clusters; (2) SMMs based on single metal (lanthanide, actinide, transition metal) ions as well as polynuclear lanthanide clusters; (3) single chain magnets; and (4) recent development of spintronics based on SMMs such as molecular spin transistors and spin valves.

Two novel complexes of CoL1(SCN)2(H2O)2 4H2O (1) and CoL2(SCN)2(H2O)2 2H2O (2) (L1 = bis(4-pyridinecarboxamide)-1,2-ethane-N,N′-dioxide and L2 = bis(4-pyridinecarboxamide-1,6-hexane)-N,N′-dioxide) constructed by pre-designed ligands of bis(4-pyridinecarboxamide)alkanes-N,N′-dioxide have been synthesized and structurally characterized. Both compounds contain similar 1D chains bridged by the ligands. However, the chains in 1 and 2 are connected by different interchain hydrogen bonds to form different 2D layers, which depend on the flexibility and length of the ligands. Furthermore, the thermal stability of 1 and 2 were studied by using thermogravimetric analysis and temperature dependent powder X-ray diffraction method.

By the reaction of Zn(OAc)(2)·2H(2)O with Ozagrel, (E)-3-(4-((1H-imidazol-1-yl)methyl)phenyl)acrylic acid (Himpaa), a novel coordination polymer [Zn(impaa)(2)](n)(1) was synthesized and was characterized by IR, elemental analysis, single-crystal X-ray diffraction analysis, photoluminescence spectroscopy, and thermogravimetric and differential thermal analysis. The four-coordinate Zn(II) ions are linked into 1D double-helical chain by the deprotonated impaa(-), which is extended into a 3D supramolecular structure through intermolecular C-H···O hydrogen bonds.

Two isostructural compounds [M(hpmc)(phen)(H 2 O)] [M = Mn (1), Co (2); H 2 hpmc = 6-hydroxypyrimidine-4-carboxylic acid, phen = 1,10-phenanthroline] were synthesized by the in-situ hydrothermal reactions of 6-chloropyrimidine-4-carboxylic acid (Clpmc) with Mn II and Co II ions, in which the metal centers are bridged by pyrimidine ring to form 1D chain. Magnetic studies indicate pyrimidine can transmit antiferromagnetic coupling and the Co II complex shows spin-canting behavior below 3.5 K.