
Talal MallahUniversity of Paris-Saclay · Institut de Chimie Moléculaire et des Matériaux d'Orsay (ICMMO)
Talal Mallah
PhD Chemistry
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268
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Introduction
Talal Mallah currently works at the Institut de Chimie Moléculaire et des Matériaux d'Orsay (ICMMO), Université Paris-Saclay. Talal does research in Inorganic Chemistry. One current project is 'Spin-Crossover Molecules on surfaces'
Publications
Publications (268)
We examine the pressure dependence of the spin-crossover transition in [Fe(pap-5NO2)2] that occurs near room temperature. We employ a combination of high-pressure calorimetry and powder X-ray diffraction measurements, conducted both under variable-pressure and variable temperature conditions. Both methods indicate that the spin-crossover transition...
A trinuclear Co(II)-containing complex was assembled using the non-innocent hexahydroxytriphenylene bridging ligand. Cyclovoltammetry and spectroelectrochemistry studies revealed that the central ligand sustained four reversible redox events, leading to different species with diverse optical behavior. Complementary analysis of the molecular structu...
A trinuclear Co(II)-containing complex was assembled using the non-innocent hexahydroxytriphenylene bridging ligand. Cyclovoltammetry and spectro-electrochemistry studies revealed that the central ligand can sustain five reversible redox events leading to different spices with diverse optical behavior. Complementary analysis of the molecular struct...
Controlling quantum spins using electric rather than magnetic fields promises significant architectural advantages for developing quantum technologies. In this context, spins in molecular nanomagnets offer tunability of spin-electric couplings (SEC) by rational chemical design. Here we demonstrate systematic control of SECs in a family of Mn(II)-co...
We synthesized a sublimable molecular spin crossover Fe(II) complex based on the Schiff base tridentate ligand qsal-NEt2 (5-diethylamino-2-((quinolin-8-ylimino)methyl)phenol). The compound undergoes a transition in temperature with a thermally induced excited...
Photoinduced spin transition is one of the fastest processes occurring in transition-metal-based molecules and materials, reaching down to tens of femtoseconds (1 fs = 10⁻¹⁵ s). The underlying dynamics have been well characterized for mononuclear Fe(ii) spin-crossover (SCO) complexes, where it was shown that the spin transition can induce coherent...
A complete theoretical analysis using first the simple Hückel model followed by more sophisticated multi‐reference calculations on a trinuclear Ni(II) complex (Tp#Ni3HHTP), bearing the non‐innocent bridging ligand HHTP³⁻, is carried out. The three semiquinone moieties of HHTP³⁻ couple antiferromagnetically and lead to a single unpaired electron loc...
Photoinduced spin transition is one of the fastest processes occurring in transition-metal-based molecules and materials, reaching down to tens of femtoseconds (1 fs = 1015 s). The underlying dynamics have been well characterized for mononuclear Fe(II) spin-crossover (SCO) complexes, where it was shown that the spin transition can induce coherent a...
We report a study of the electron transport (ET) properties at the nanoscale (conductive-AFM noted C-AFM thereafter) of individual Prussian Blue Analog (PBA) cubic nanocrystals (NCs) of CsCo III Fe II , with size...
A single layer of a dyad made of a cobalt(II) bis‐terpyridine complex functionalized with a Boron‐dipyrromethene (BODIPY) fluorophore on transparent Indium Tin Oxide (ITO) electrode is prepared. A modulation of the photoluminescence intensity of the fluorophore upon the application of an electric stimulus on the ITO electrode that supports 10 picom...
Spin-crossover molecules present the unique property of having two spin states that can be controlled by light excitation at low temperature. Here, we report on the photoexcitation of [FeII((3, 5-(CH3)2Pz)3BH)2] (Pz = pyrazolyl) ultrathin films, with thicknesses ranging from 0.9 to 5.3 monolayers, adsorbed on Cu(111) substrate. Using X-ray absorpti...
In this paper, we discuss in the framework of a mechanoelastic model the electronic and mechanical behavior of a single layer of spin crossover molecules self-organized on a substrate. We consider the molecules situated in a face-centered-cubic structure interacting in between and with sites in the substrate by the way of connecting springs with gi...
This chapter is devoted to theoretical calculations aimed at determining the electronic structure of binuclear complexes, including isotropic and anisotropic interactions in both the strong and in the weak-exchange coupling limits. The theory of effective Hamiltonians is used to extract magnetic anisotropy terms in various regimes and in particular...
Seven dimeric metallacrowns (MC) based on Ln[12‐MCM(III)N(shi)‐4], where LnIII=Dy, Ho, Yb, or Y, MIII=Mn or Ga, and shi³⁻ is salicylhydroximate, have been synthesized and characterized by single‐crystal X‐ray diffraction, and for the dysprosium‐manganese dimers, the magnetic properties have been measured. In each dimer two Ln[12‐MCM(III)N(shi)‐4] u...
In this paper we study the out-of-equilibrium dynamics associated with photoinduced charge-transfer (CT) in cyanide-bridged Co-Fe Prussian blue analogue nanocrystals. In these coordination networks, the structural trapping of the photoinduced CT polaron involves local electronic and structural reorganizations. Femtosecond X-ray and optical absorpti...
Two new photo-switchable terphenylthiazole molecules are synthesized and self-assembled as monolayers on Au and on ferromagnetic Co electrodes. The electron transport properties probed by conductive atomic force microscopy in ultra-high vacuum reveal a larger conductance of the light-induced closed (c) form than for the open (o) form. We report an...
Two new photo-switchable terphenylthiazoles molecules are synthesized and self-assembled as monolayers on Au and on ferromagnetic Co electrodes. The electron transport properties probed by conductive atomic force microscopy in ultra-high vacuum reveal a conductance of the light-induced closed (c) form larger than for the open (o) form. We report an...
The collective magnetic behavior of photoswitchable 11 nm cyanide-bridged nanoparticles based of the Prussian blue analogue CsCoFe were investigated when embedded in two different matrices with different concentrations. The effect of the intensity of light irradiation was studied in the less concentrated sample. Magnetization studies and alternatin...
Changing the anion in a crystal lattice induces distinct structural distortions in the [CoS4]²⁺ core for a family of complexes with the general molecular formula [Co(L1)4]X2, where L1 = thiourea (NH2CSNH2) and X = I (1), Br (2), and [Co(L1)4](SiF6) (3). The magnetic anisotropy (D) for 1-3 was quantitatively determined with a magnitude of -153(2), -...
The tris pyrazolyl borate ligand imposes a rigid scaffold around Fe( ii ) ensuring a robust magnetic anisotropy when the molecules assembled as monolayers suffer from the dissymmetric environment of the substrate/vacuum interface.
The measurement of the magnetic anisotropy of [Fe{(3,5-(CH3)2Pz)3BH}2], where Pz = pyrazole, in its high spin S =2 state by X-ray Magnetic Circular Dichroism (XMCD) spectroscopy when assembled as an...
We report the existence of a sizeable quantum tunnelling splitting between the two lowest electronic spin levels of mononuclear Ni complexes. The level anti-crossing, or magnetic clock transition, associated with this gap has been directly monitored by heat capacity experiments. The comparison of these results with those obtained for a Co derivativ...
Front cover of the article :
"Electrical Readout of Light-Induced Spin Transition in Thin Film Spin Crossover/Graphene Heterostructure"
Nikita Konstantinov et al.
Journal of Materials Chemistry C, 2021, 9, 2712 - 2720
Weblink to the article : http://xlink.rsc.org/?DOI=D0TC05202G
We report the existence of a sizeable quantum tunnelling splitting between the two lowest electronic spin levels of mononuclear Ni complexes. The level anti-crossing, or magnetic "clock transition", associated with this gap has been directly monitored by heat capacity experiments. The comparison of these results with those obtained for a Co derivat...
Bistable spin-crossover molecules are particularly interesting to the development of innovative electronic and spintronic devices as they present two spin states that can be controlled by external stimuli. In this purpose, being able to switch at will the spin state of a single molecule in a dense molecular array is a key milestone. However, the el...
Magneto-opto-electronic properties are shown for a hybrid device constructed from a spin crossover (SCO) thin film of the Fe[HB(3,5-(Me)2Pz)3]2 molecular material evaporated over a graphene sensing layer. The principle of electrical detection of the light-induced spin transition in SCO/graphene heterostructures is demonstrated. The switchable spin...
We have developed a general protocol for the preparation of hybrid nanostructures formed by nanoparticles (NPs) of molecule-based magnets based on Prussian Blue Analogues (PBAs) decorated with plasmonic Au NPs...
Photoinduced charge-transfer is an important process in nature and technology and is responsible for the emergence of exotic functionalities, such as magnetic order for cyanide-bridged bimetallic coordination networks. Despite its broad interest and intensive developments in chemistry and material sciences, the atomic-scale description of the initi...
Two Gd III Fe III 4 metallacrown complexes are presented and analyzed for their magnetic properties. One of these species is newly identified and exhibits a bent ring geometry as opposed to the more...
The magnetic anisotropy parameters of a hexacoordinate trigonally elongated Ni(II) complex with symmetry close to D3d are measured using field-dependent magnetization and High-Field and High-Frequency EPR spectroscopy (D = + 2.95 cm−1, |E/D| = 0.08 from EPR). Wave function based theoretical calculations reproduce fairly well the EPR experimental da...
We report electron transport measurements through nano-scale devices consisting of 1 to 3 Prussian blue analog (PBA) nanocrystals connected between two electrodes. We compare two types of cubic nanocrystals, CsCoIIIFeII (15 nm) and CsNiIICrIII (6 nm), deposited on highly oriented pyrolytic graphite and contacted by conducting-AFM. The measured curr...
We report electron transport measurements through nano-scale devices consisting of 1 to 3 Prussian blue analog (PBA) nanocrystals connected between two electrodes. We compare two types of cubic nanocrystals, CsCoFe (15 nm) and CsNiCr (6 nm), deposited on highly oriented pyrolytic graphite and contacted by conducting-AFM. The measured currents show...
Photoswitchable 11 nm nanocrystals with the coordination network Cs{Co[Fe(CN)6]} were obtained using a template-free method. The nanocrystals were recovered from the colloidal solutions as solid materials surrounded by cetyltrimethylammonium (CTA) cations or embedded in the organic polymer polyvinylpyrrolidone (PVP). Complementary magnetic, spectro...
Light‐induced spin‐state switching is one of the most attractive properties of spin‐crossover materials. In bulk, low‐spin (LS) to high‐spin (HS) conversion via the light‐induced excited spin‐state trapping (LIESST) effect may be achieved with a visible light, while the HS‐to‐LS one (reverse‐LIESST) requires an excitation in the near‐infrared range...
Substrate‐induced switching: A FeII spin‐crossover molecule at the interface with metals switches from a high‐spin to low‐spin state with visible light. This result is the complete opposite of what is known for the bulk materials. Therefore, for spin‐crossover compounds, the interface matters.
Abstract
Light‐induced spin‐state switching is one of...
We report the preparation and the full characterization of a novel mononuclear trigonal bipyramidal Co II complex [Co(NS 3 iPr )Br](BPh 4 ) ( 1 ) with the tetradentate sulphur containing ligand NS 3 iPr (N(CH 2 CH 2 SCH(CH 3 ) 2 ) 3 ). The comparison of its magnetic behaviour with those of two previously reported compounds [Co(NS 3 iPr )Cl](BPh 4 )...
Collective spin excitations in magnetically ordered materials are exploited for advanced applications in magnonics and spintronics. In these contexts, conditions for minimizing dissipative effects are sought in order to obtain long living excitations that can be coherently manipulated. Organic and coordination materials may offer alternative option...
Two series of lanthanide complexes have been chosen to analyze trends in the magnetic properties and crystal field parameters (CFPs) along the two series: The highly symmetric LnZn16(picHA)16 series (Ln=Tb, Dy, Ho, Er, Yb; picHA=picolinohydroxamic acid) and the [Ln(dpa)3](C3H5N2)3⋅3H2O series (Ln=Ce–Yb; dpa=2,6‐dipicolinic acid) with approximate th...
Prussian Blue Nanoparticles and Nanocomposites
Synthesis, Devices, and Applications
A trinuclear triphenylene trisemiquinone complex containing paramagnetic NiII is obtained under ambient condition from the reaction of the deprotonated tricatecholate hexahydroxytriphenylene (H6HHTP) with NiII capped with a trispyrazolyl borate tridentate ligand. The magnetic and EPR data are consistent with a delocalization of the electronic spin...
Luminescence from Isolated Tb-based Metallacrown Molecular Complexes on h-BN - Volume 25 Supplement - Steffi Y. Woo, Talal Mallah, Vincent Pecoraro, Mathieu Kociak, Odile Stéphan, Alberto Zobelli
Spin-crossover molecules are very appealing for use in multifunctional spintronic devices because of their ability to switch between high-spin and low-spin states with external stimuli such as voltage and light. In actual devices, the molecules are deposited on a substrate, which can modify their properties. However, surprisingly little is known ab...
Four mononuclear cobalt(II) complexes with pseudo tetrahedral geometry were isolated with different counteranions; their structure solution reveals the molecular formula as [Co(L1)4]X2 [where L1 = thiourea (NH2CSNH2) and X = NO3 (1), Br (2), and I (3)] and [Co(L1)4](SiF6) (4). The detailed analysis of direct-current (dc) magnetic data reveals a zer...
Recent advances in structural control during the synthesis of SWCNTs have in common the use
of bimetallic nanoparticles as catalysts, despite the fact that their exact role is not fully understood.
We, therefore, analyze the effect of the catalyst’s chemical composition on the structure of
the resulting SWCNTs by comparing three bimetallic catalyst...
Recent advances in structural control during the synthesis of SWCNTs have in common the use of bimetallic nanoparticles as catalysts, despite the fact that their exact role is not fully understood. We therefore analyze the effect of the catalyst' s chemical composition on the structure of the resulting SWCNTs by comparing three bimetallic catalysts...
Spin crossover compounds are multifunctional switching materials that change their spin state and many other physical properties, such as colour, magnetic susceptibility, electric conductivity, dielectric constant and mechanical properties, upon external stimuli. Spin crossover materials have been proposed for a variety of technological application...
In this Article, we have investigated the influence of substituents on a ligand in determining both the magnitude and sign of D in a family of cobalt(II) complexes with the molecular formula [Co(L1)2X2], where L1 = tetramethylthiourea and X = Cl, Br, and I (1−3, respectively), compared with their parent complexes ([Co(L)2X2] [L = thiourea and X = C...
We report a bimetallic holmium(III) complex showing a S-shaped magnetic hysteresis at low temperature. The complex is investigated by x-ray crystallography, magnetometry, single crystal microsquid measurements, and first-principles calculations. A model Hamiltonian including electronic and nuclear magnetic moments is used to fit all experimental da...
Understanding the properties of spin-crossover molecules in direct contact with metals is crucial for their future integration in electronic and spintronic devices. Here, by x-ray absorption spectroscopy, we investigate the properties of FeII((3,5}-(CH3)2Pz)3BH)2 molecules in the form of monolayer islands on a metallic substrate, namely Au(111). We...
We present a thorough tight-binding analysis of the band structure of a wide variety of lattices belonging to the class of honeycomb and Kagome systems including several mixed forms combining both lattices. The band structure of these systems are made of a combination of dispersive and flat bands. The dispersive bands possess Dirac cones (linear di...
We investigate the size-dependent bistability of a FeII[HB(3,5-(Me)2Pz)3]2 spin-transition compound in the form of thin films, the thickness of which varies from 130 to 8500 nm. From combined structural, magnetic and optical measurements, we demonstrate that the materials prepared by sublimation consist in crystalline grains of the triclinic phase...
The preparation of a tetranuclear Ni(II) complex, made of two binuclear species bridged by a nitrate anion, using a macrocyclic cryptand like ligand is reported. The metal ions within the binuclear species are hexacoordinate with different distorted environments. One nickel site, Ni1, has as a compressed octahedral geometry, while the other nickel...
The preparation of a binuclear Ni(II) complex with a pentacoordinate environment using a cryptand organic ligand and the imidazolate bridge is reported. The coordination sphere is close to trigonal bipyramidal (tbp) for one Ni(II) and to square pyramidal (spy) for the other. The use of the imidazolate bridge that undergoes π-π stacking with two ben...
We study the transient electron transfer process in CsCoFe and RbMnFe Prussian Blue Analogues (PBA), by time-resolved X-ray Absorption Near Edge Structure (XANES) and by time-resolved optical spectroscopy. We performed time-resolved studies on CsCoFe nanocrystals dispersed in solution. The XANES results obtained at room temperature clearly evidence...
Catalyst engineering is a key point for selective growth of single-walled carbon nanotubes (SWCNT) with chemical vapor deposition (CVD). Here, we develop a new general synthesis method able to produce a wide range of homogenous bimetallic catalyst nanoparticles with controlled stoichiometry and sizes. The basics of this catalyst synthesis is to use...
The preparations of related mononuclear and binuclear Co(II) complexes with a quasi-identical local C3v symmetry using a cryptand organic ligand are reported. The mononuclear complex behaves as a single molecule magnet (SMM). A relatively weak antiferromagnetic exchange coupling (J) of the same order of magnitude as the local magnetic anisotropy (D...
This review is dedicated to the synthesis, properties and potential applications of Prussian blue analogs and other cyanide-bridged coordination polymers that have been recently investigated at the nanoscale. A wide range of nanostructures including core-shells, hollow particles and other architectures were designed with the objective of creating n...
Prussian blue analogues (PBA) ferromagnetic nanoparticles CsIxNiII[CrIII(CN)6 ]z·3(H2O) embedded in CTA+ (cetyltrimethylammonium) matrix have been investigated by magnetometry and magnetic small-angle neutron scattering (SANS). Choosing particle sizes (diameter D = 4.8 and 8.6 nm) well below the single-domain radius and comparable volume fraction o...
This paper describes the correlation between Ising-type magnetic anisotropy and structure in trigonal bipyramidal Co(II) complexes. Three sulfur-containing trigonal bipyramidal Co(II) complexes were synthesized and characterized. It was shown that we can engineer the magnitude of the Ising anisotropy using ligand field theory arguments in conjuncti...