Light emitting semiconducting quantum dots show great promise as solar cells, optoelectronic devices and multimodal imaging probes. Here we demonstrate successful grafting of a thiol-functionalised GdIII MRI contrast agent onto the surface of core-multishell CdSe/CdS/ZnS quantum dots. The resulting nanoprobe exhibits intense photoluminescence and unprecedentedly large T1 relaxivity of 6800 mM−1 s−1 per nanoparticle due to secure implanting of ca. 620 magnetic centers per quantum dot unit.

AbstractLiquid exfoliated, atomically thin semiconducting transition metal dichalcogenides (TMDs), as inorganic equivalents of graphene, have attracted great interest due to their distinctive physical, optoelectronic, and chemical properties. Functionalization of 2D TMDs brings new prospects for applications in optoelectronics, quantum technologies, catalysis, and medicine. In this report, dual functionalization of 2D semiconducting 2H-MoS2 nanosheets through simultaneous incorporation of magnetic and luminescent properties is demonstrated. A facile method is proposed for tuning the properties of the TDM semiconductors and accessing multimodal platforms, consisting in covalent grafting of lanthanide complexes onto the surface of 2D TMDs. Dual functionalization of liquid-exfoliated MoS2 nanosheets is demonstrated simultaneously with both europium (III) and gadolinium (III) complexes to form a colloidally stable luminescent (with millisecond lifetimes) and paramagnetic MoS2-based nanohybrid material. This work is the first example of transition metal dichalcogenide nanosheets functionalized with preformed lanthanide complexes. These findings open new prospects for covalent functionalization of TMDs with molecular species bearing specific functionalities as a means to tune the optoelectronic properties of the semiconductors, in order to create advanced materials and devices with a wide range of functionalities.

•f-SIMs hold enormous promise for quantum information technologies.•Control of coordination environments produces high-performance SIMs.•Actinides engage in stronger magnetic exchange than lanthanides.•QIP could be feasible using quantum states in f-element SIMs.Over the past fifteen years or so, the study of f-element single-ion magnets (f-SIMs) has gone from being a sub-discipline of molecular magnetism to an established field of research in its own right. The major driving force has been their exceptional promise in applications such as ultra-high-density data storage, spintronics, and quantum information processing (QIP). Recent demonstrations that f-SIMs preserve their intrinsic magnetic properties even when deposited onto substrates have reinforced the interests in the field.Here, we review the current state of the field of lanthanide and actinide f-SIMs; discuss the principal factors affecting the magnetic and quantum properties of such single-ion magnets; review the latest chemical approaches in designing f-SIMs with superior properties; and highlight new trends in single molecule magnetism, including using f-SIMs as potential spin qubits for quantum computers.Download high-res image (121KB)Download full-size image

The reaction of the hydrazone, 2-methoxy-6-(pyridin-2-yl-hydrazonomethyl) phenol (LH) with lanthanide(III) nitrate salts in the presence of excess triethylamine afforded the heptanuclear Ln(III) complexes: [Gd7(L)6(μ3-OH)8(NO3)4(H2O)]·(NO3)3·8CH3CN·H2O (1), [Tb7(L)6(μ3-OH)8(NO3)4]·(NO3)3·9CH3CN·2CH3OH·3H2O (2), [Dy7(L)6(μ3-OH)8(NO3)4(H2O)]·(NO3)3·7CH3CN·3H2O (3), [Ho7(L)6(μ3-OH)8(NO3)4]·(NO3)3·11CH3CN·2CH3OH·2H2O (4) and [Er7(L)6(μ3-OH)8(NO3)4]·(NO3)3·8CH3CN·2CH3OH (5). Single crystal X-ray diffraction studies reveal that these complexes are tri-cationic, possessing three nitrate counter anions. The heptanuclear ensemble is non-planar and consists of six [L]− and eight μ3-OH ligands. These compounds show an interesting structural motif with two incomplete cubes fused to each other through a common Ln(III) ion. Compound 1 exhibits a magnetocaloric effect, with (−ΔSm(T) = 27.7 J kg−1 K−1 at 3 K and under a field change of 0–7 T), while compound 3 shows slow magnetic relaxation at very low temperatures.

The sequential reaction of the multisite coordination ligand 6,6′-{(2-(dimethylamino)ethyl azanediyl)bis(methylene)}bis(2-methoxy-4-methylphenol) (LH2) with LnIII salts (Ln = Gd, Tb, Dy) and Co(ClO4)2·6H2O in the presence of triethylamine and pivalic acid (pivH) in ambient conditions afforded a series of isostructural heterometallic hexanuclear CoII/LnIII complexes with the general formula [CoII2Ln4(μ3-OH)4(L)2(piv)8(μ-OH2)]·wCH3C·xCH2Cl2·yCH3OH·zH2O (1: Ln = Gd, w = 5, x = 2, y = 0, z = 2; 2: Ln = Tb, w = 7, x = 4, y = 2, z = 0; 3: Ln = Dy; w = 4, x = 2, y = 2, z = 0). Compounds 1 and 3 crystallize in the monoclinic system, space group P21/n (Z = 4), while compound 2 crystallizes in P2/n (Z = 2). The hexanuclear core of the complexes comprises of a nonplanar arrangement of lanthanide ions bridged by two μ3-OH ligands. This tetranuclear motif is connected to the CoII ions by two μ3-OH ligands. The overall structure contains four interlinked incomplete cubic subunits (two CoIILnIII2O4 and two LnIII3O4) that are connected to each other by the sharing of two LnIII ions. The lanthanide centers are eight-coordinate (distorted trigonal-dodecahedron) and nine-coordinate (distorted monocapped square-antiprism), while the cobalt centers are six-coordinate (distorted octahedral). Magnetic measurement of the dysprosium analogue shows a slow magnetic relaxation.

The reaction of lanthanide(III) salts with an organodiphosphonic acid under hydrothermal conditions resulted in a P–C bond cleavage affording [{Eu4(PO4)(PO4)0.5×4(PO4)0.25×4(H2O)2}·6H2O]n (1), [{Dy4(PO4)(PO4)0.5×4(PO4)0.25×4(H2O)2}·6H2O]n (2), and [{Gd(PO4)0.5(PO4)0.5(H2O)3}·2H2O]n (3). 1 and 2 are porous 3D coordination polymers whose repeating units possess a dimeric motif. While one lanthanide ion in the dimer is eight-coordinate in a distorted square-antiprismatic geometry, the other is nine-coordinate and present in a distorted monocapped square-antiprismatic geometry. In contrast to 1 and 2, 3 possesses a 2D architecture; the asymmetric unit contains a monomeric GdIII center which is nine-coordinate in a distorted monocapped square-antiprismatic geometry.

The reaction of 2-methoxy-6-(pyridin-2-ylhydrazonomethyl)phenol (LH) with Ln(III) (Ln = Gd, Tb, Dy, Ho) salts in the presence of an excess of triethylamine afforded [Gd4(L)4(μ4-OH)(μ3-OH)2(NO3)4]·(NO3)·4CH3CN·CH3OH·2H2O (1), [Tb4(L)4(μ4-OH)(μ3-OH)2(NO3)4]·(NO3)·4CH3CN·3H2O (2), [Dy4(L)4(μ4-OH)(μ3-OH)2(NO3)4]·(NO3)·6CH3CN·H2O (3), and [Ho4(L)4(μ4-OH)(μ-OH)2(NO3)4]·(NO3)·8CH3CN·3CH3OH·2H2O (4). All four complexes contain a monocationic tetranuclear core with a unique seesaw topology. The tetranuclear assembly is formed through the coordination of four [L]−, one μ4-OH, two μ3-OH, and four chelating nitrate ligands, with a charge-balancing nitrate counteranion. Magnetic studies reveal a weak antiferromagnetic coupling throughout the series. Compound 1 can be modeled well with an isotropic exchange between all centers parametrized by J = −0.09 cm–1. Compound 3 exhibits slow magnetic relaxation at low temperatures.

Three new binuclear helicates, [M2L2]·3DMF (M = Co(II), 1, Zn(II), 3) and [Cu2L2]·DMF·0.4H2O (2), have been assembled using the helicand H2L that results from the 2:1 condensation reaction between o-vanillin and 4,4′-diaminodiphenyl ether. The metal ions within the binuclear helicates are tetracoordinated with a distorted tetrahedral geometry. Direct current magnetic characterization and EPR spectroscopy of the Co(II) derivative point to an easy axis type anisotropy for both Co(II) centers, with a separation of at least 55 K between the two doublets. Dynamic susceptibility measurements evidence slow relaxation of the magnetization in an applied dc field. Since the distance between the cobalt ions is quite large (11.59 Å), this is attributed in a first instance to the intrinsic properties of each Co(II) center (single-ion magnet behavior). However, the temperature dependence of the relaxation rate and the absence of slow dynamics in the Zn(II)-doped sample suggest that neither the simple Orbach mechanism nor Raman or direct processes can account for the relaxation, and collective phenomena have to be invoked for the observed behavior. Finally, due to the rigidization of the two organic ligands upon coordination, the pure zinc derivative exhibits fluorescence emission in solution, which was analyzed in terms of fluorescence quantum yields and lifetimes.

Synthesis and structure of a cyclic tetranuclear Ni2Gd2 complex bridged by amino acidato ligands, with an S = 9 spin ground state, derived from ferromagnetic spin-coupling between SGd = 7/2 and SNi = 1 are reported.

The reaction of the hydrazone, 2-methoxy-6-(pyridin-2-yl-hydrazonomethyl) phenol (LH) with lanthanide(III) nitrate salts in the presence of excess triethylamine afforded the heptanuclear Ln(III) complexes: [Gd7(L)6(μ3-OH)8(NO3)4(H2O)]·(NO3)3·8CH3CN·H2O (1), [Tb7(L)6(μ3-OH)8(NO3)4]·(NO3)3·9CH3CN·2CH3OH·3H2O (2), [Dy7(L)6(μ3-OH)8(NO3)4(H2O)]·(NO3)3·7CH3CN·3H2O (3), [Ho7(L)6(μ3-OH)8(NO3)4]·(NO3)3·11CH3CN·2CH3OH·2H2O (4) and [Er7(L)6(μ3-OH)8(NO3)4]·(NO3)3·8CH3CN·2CH3OH (5). Single crystal X-ray diffraction studies reveal that these complexes are tri-cationic, possessing three nitrate counter anions. The heptanuclear ensemble is non-planar and consists of six [L]− and eight μ3-OH ligands. These compounds show an interesting structural motif with two incomplete cubes fused to each other through a common Ln(III) ion. Compound 1 exhibits a magnetocaloric effect, with (−ΔSm(T) = 27.7 J kg−1 K−1 at 3 K and under a field change of 0–7 T), while compound 3 shows slow magnetic relaxation at very low temperatures.

Synthesis and structure of a cyclic tetranuclear Ni2Gd2 complex bridged by amino acidato ligands, with an S = 9 spin ground state, derived from ferromagnetic spin-coupling between SGd = 7/2 and SNi = 1 are reported.