Inorganics, Volume 6, Issue 2 (June 2018) – 28 articles

Nanostructured dye-sensitized solar cells (DSSCs) are promising photovoltaic devices because of their low cost and transparency. Ruthenium polypyridine complexes have long been considered as lead sensitizers for DSSCs, allowing them to reach up to 11% conversion efficiency. However, ruthenium suffers from serious drawbacks potentially limiting its widespread applicability, mainly related to its potential toxicity and scarcity. This has motivated continuous research efforts to develop valuable alternatives from cheap earth-abundant metals, and among them, iron is particularly attractive. Making iron complexes applicable in DSSCs is highly challenging due to an ultrafast deactivation of the metal–ligand charge-transfer (MLCT) states into metal-centered (MC) states, leading to inefficient injection into TiO₂. In this review, we present our latest developments in the field using Fe(II)-based photosensitizers bearing N-heterocyclic carbene (NHC) ligands, and their use in DSSCs. Special attention is paid to synthesis, photophysical, electrochemical, and computational characterization. Full article

We report the synthesis, structural and magnetic characterization of five mononuclear Dy^III ion complexes using triphenylphosphine oxide as a monodentate ligand. They have formulae [Dy^III(OPPh₃)₃(NO₃)₃] (1), [Dy^III(OPPh₃)₄(NO₃)₂](NO₃) (2), [Dy^III(OPPh₃)₃Cl₃] (3), [Dy^III(OPPh₃)₄Cl₂]Cl (4) and [Dy^III(OPPh₃)₄Cl₂](FeCl₄) (5). These complexes are characterized using single crystal X-ray diffraction, which revealed that each complex has a unique coordination environment around the Dy^III ion, which results in varying dynamic magnetic behavior. Ab initio calculations are performed to rationalize the observed magnetic behavior and to understand the effect that the ligand and coordination geometry around the Dy^III ion has on the single-molecule magnet (SMM) behavior. In recent years, seven coordinate Dy^III complexes possessing pseudo ~D_5h symmetry are found to yield attractive blocking temperatures for the development of new SMM complexes. However, here we show that the strength of the donor ligand plays a critical role in determining the effective energy barrier and is not simply dependent on the geometry and the symmetry around the Dy^III ion. Seven coordinate molecules possessing pseudo D_5h symmetry with strong equatorial ligation and weak axial ligation are found to be inferior, exhibiting no SMM characteristics under zero-field conditions. Thus, this comprehensive study offers insight on improving the blocking temperature of mononuclear SMMs. Full article

The illumination direction and temperature can greatly affect the performance of dye-sensitized solar cells (DSSCs) when practical non-volatile solvents are used with bulky one-electron redox mediators such as cobalt tris(bipyridine). For higher performance, a tandem electrolyte system consisting of cobalt tris(bipyridine) with tris(4-methoxyphenyl)amine was used. Discrepancies in J–V hysteresis were investigated by using photocurrent turn-on transients, open-circuit voltage decay, and electrochemical impedance spectroscopy. The devices perform much better upon illumination form the counter electrode side and exhibit much less hysteresis and more stabilized power output as characterized by maximum power-point tracking (MPP) tracking. Full article

Nickel nitrate diammine, Ni(NH₃)₂(NO₃)₂, can be synthesised from the thermal decomposition of nickel nitrate hexammine, Ni[(NH₃)₆](NO₃)₂. The hexammine decomposes in two distinct major stages; the first releases 4 equivalents of ammonia while the second involves the release of NO_x, N₂, and H₂O to yield NiO. The intermediate diammine compound can be isolated following the first deammoniation step or synthesised as a single phase from the hexammine under vacuum. Powder X-ray diffraction (PXD) experiments have allowed the structure of Ni(NH₃)₂(NO₃)₂ to be solved for the first time. The compound crystallises in orthorhombic space group Pca2₁ (a = 11.0628 (5) Å, b = 6.0454 (3) Å, c = 9.3526 (4) Å; Z = 4) and contains 11 non-hydrogen atoms in the asymmetric unit. Fourier transform infrared (FTIR) spectroscopy demonstrates that the bonding in the ammine is consistent with the structure determined by PXD. Full article

Molecular engineering of high energy barrier U_eff in single-molecule magnets (SMMs) of general composition Mo^III_kV^II_m based on orbitally-degenerate pentagonal-bipyramidal [Mo_III(CN)₇]⁴⁻ complexes with unquenched orbital momentum and high-spin V(II) complexes is discussed. In these SMMs, the barrier originates exclusively from anisotropic Ising-type exchange interactions −J_xy(S_i^xS_j^x + S_i^yS_j^y) − J_zS_i^zS_j^z in the apical cyano-bridged pairs Mo^III–CN–V^II, which produce a double-well energy profile with a doubly degenerate ground spin state ±M_S. It is shown that the spin-reversal barrier U_eff is controlled by anisotropic exchange parameters J_z, J_xy, and the number n of apical Mo^III–CN–V^II groups in a SMM cluster, U_eff ~ 0.5|J_z − J_xy|n; it can reach a value of many hundreds of wavenumbers (up to 741 cm⁻¹). This finding provides a very efficient straightforward strategy for further scaling U_eff to high values (>1000 cm⁻¹) by means of enhancing exchange parameters J_z, J_xy, and increasing the number of [Mo^III(CN)₇]⁴⁻ complexes in a SMM molecule. Full article

Surface-bound heteroleptic copper(I) dyes [Cu(L_anchor)(L_ancillary)]⁺ are assembled using the “surfaces-as-ligands, surfaces as complexes” (SALSAC) approach by three different procedures. The anchoring and ancillary ligands chosen are ((6,6′-dimethyl-[2,2′-bipyridine]-4,4′-diyl)-bis(4,1-phenylene))bis(phosphonic acid) (3) and 4,4′-bis(4-iodophenyl)-6,6′-diphenyl-2,2′-bipyridine (4), respectively. In the first SALSAC procedure, the FTO/TiO₂ electrode is functionalized with 3 in the first dye bath, and then undergoes ligand exchange with the homoleptic complex [Cu(4)₂][PF₆] to give surface-bound [Cu(3)(4)]⁺. In the second method, the FTO/TiO₂ electrode functionalized with 3 is immersed in a solution containing a 1:1 mixture of [Cu(MeCN)₄][PF₆] and 4 to give surface-anchored [Cu(3)(4)]⁺. In the third procedure, the anchor 3, copper(I) ion and ancillary ligand 4 are introduced in a sequential manner. The performances of the DSSCs show a dependence on the dye assembly procedure. The sequential method leads to the best-performing DSSCs with the highest values of J_SC (7.85 and 7.73 mA cm⁻² for fully masked cells) and overall efficiencies (η = 2.81 and 2.71%, representing 41.1 and 39.6% relative to an N719 reference DSSC). Use of the 1:1 mixture of [Cu(MeCN)₄][PF₆] and 4 yields DSSCs with higher V_OC values but lower J_SC values compared to those assembled using the sequential approach; values of η are 2.27 and 2.29% versus 6.84% for the N719 reference DSSC. The ligand exchange procedure leads to DSSCs that perform relatively poorly. The investigation demonstrates the versatile and powerful nature of SALSAC in preparing dyes for copper-based DSSCs, allowing the photoconversion efficiency of dye to be optimized for a given dye. The SALSAC strategy provides alternative hierarchical strategies where the isolation of the homoleptic [Cu(L_ancillary)₂]⁺ is difficult or time-consuming; stepwise strategies are more atom-economic than ligand exchange involving the homoleptic [Cu(L_ancillary)₂]⁺. Full article

Herein, we describe the preparation, characterization and photophysical properties of neutral lanthanide complexes containing a redox-active ligand 1-(2-pyridylazo)-2-phenanthrol (papl). The complexes likely share similar structural features and bear the formulation Ln(papl)₃ (Ln(III) = Gd, Dy, Tb), which is supported by electrospray ionization mass spectrometry, CHN analysis, FT-IR and UV–Vis spectroscopy. The synthesis and structural properties of a related complex, Ho(qapl)₃ (where qapl = 10-(8-quinolylazo)-9-phenanthrol), is also reported. The complexes feature ligand-centered redox activity, similar to other reported transition metal complexes with papl. Variable temperature magnetic susceptibility measurements (DC and AC) suggest typical free-ion magnetism without any slow-relaxation dynamics. The photophysical properties of the ligand and complexes were investigated and the results of emission spectroscopy indicate ligand-centered processes. Full article

This paper reports the synthesis of Fe-titanate nanotubes by means of the conventional ion-exchange method with iron nitrate solutions. As the iron-rich nanotubes were found to contain the catalyst precursor intrinsically dispersed in their structures, the unprecedented possibility of using this kind of materials for building carbon nanostructures, firmly attached at the surface of the forming TiO₂ nanoparticles, was verified. The catalytic decomposition of ethylene, used as a carbon source, was performed at a relatively high temperature (750 °C) when the nanotubes undergo an irreversible phase transformation to form anatase and rutile nanoparticles. Due to the different amounts of Fe ions in the nanotubes, distinct types of carbon/TiO₂ hybrid interfaces were formed, ranging from amorphous (lower Fe³⁺ concentration) to the more crystalline graphitic domains (higher Fe³⁺ concentrations), as documented by the microstructure of the treated samples. The present approach is of potential interest for (photo)catalytic and energy conversion/transport applications. Full article

Reactivity studies of silyliumylidenes remain scarce with only a handful of publications to date. Herein we report the activation of S–H bonds in hydrogen sulfide by mTer-silyliumylidene ion A (mTer = 2,6-Mes₂-C₆H₃, Mes = 2,4,6-Me₃-C₆H₂) to yield an NHC-stabilized thiosilaaldehyde B. The results of NBO and QTAIM analyses suggest a zwitterionic formulation of the product B as the most appropriate. Detailed mechanistic investigations are performed at the M06-L/6-311+G(d,p)(SMD: acetonitrile/benzene)//M06-L/6-311+G(d,p) level of density functional theory. Several pathways for the formation of thiosilaaldehyde B are examined. The energetically preferred route commences with a stepwise addition of H₂S to the nucleophilic silicon center. Subsequent NHC dissociation and proton abstraction yields the thiosilaaldehyde in a strongly exergonic reaction. Intermediacy of a chlorosilylene or a thiosilylene is kinetically precluded. With an overall activation barrier of 15 kcal/mol, the resulting mechanistic picture is fully in line with the experimental observation of an instantaneous reaction at sub-zero temperatures. Full article

In dye-sensitized solar cells (DSCs), the redox mediator is responsible for the regeneration of the oxidized dye and for the hole transport towards the cathode. Here, we introduce new copper complexes with tetradentate 6,6′-bis(4-(S)-isopropyl-2-oxazolinyl)-2,2′-bipyridine ligands, Cu(oxabpy), as redox mediators. Copper coordination complexes with a square-planar geometry show low reorganization energies and thus introduce smaller losses in photovoltage. Slow recombination kinetics of excited electrons between the TiO₂ and Cu^II(oxabpy) species lead to an exceptionally long electron lifetime, a high Fermi level in the TiO₂, and a high photovoltage of 920 mV with photocurrents of 10 mA∙cm⁻² and 6.2% power conversion efficiency. Meanwhile, a large driving force remains for the dye regeneration of the Y123 dye with high efficiencies. The square-planar Cu(oxabpy) complexes yield viscous gel-like solutions. The unique charge transport characteristics are attributed to a superposition of diffusion and electronic conduction. An enhancement in charge transport performance of 70% despite the higher viscosity is observed upon comparison of Cu(oxabpy) to the previously reported Cu(tmby)₂ redox electrolyte. Full article

In this review, we discuss the main directions in which ruthenium complexes for dye-sensitized solar cells (DSCs) were developed. We critically discuss the implemented design principles. This review might be helpful at this moment when a breakthrough is needed for DSC technology to prove its market value. Full article

Tetranuclear complexes [M₄(L^R)₄] with M = Ni(II) or Zn(II), with a [2 × 2] grid-type structure, were assembled in good yields and purity from the easily accessible but unprecedented pyrazine-bridged bis(thiosemicarbazone) protoligands (ligand precursors) H₂L^R (1,4-pyrazine-2,5-bis(R-carbaldehyde-thiosemicarbazone); R = Me, Et, ⁱPr, or Ph). The complexes were characterised in solution by NMR, MS, IR, and UV-Vis absorption spectroscopy and (spectro)electrochemical methods. HR-MS spectra unequivocally reveal that the tetranuclear species are very stable in solution and any measurements represent these species. Only at higher temperatures (fragmentation in solution: MS and in the solid: TG-DTA) or upon the addition of protons (acidic UV-Vis titrations) can the tetrameric entities be decomposed. Single crystal XRD measurement remained preliminary. Rapid loss of co-crystallised solvent molecules within the [2 × 2] grid-type structures resulted in crystals of very poor quality, but the results were qualitatively in line with spectroscopy, electrochemistry, and quantum chemical (DFT) calculations. IR and NMR spectroscopy point clearly to a thiolate coordination of dianionic (deprotonated) ligands. The electrochemistry reveals four electronically coupled and reversible one-electron reductions centred largely at the pyrazine bridges. EPR and UV-Vis spectroelectrochemical measurements in combination with DFT calculation support the assignment. Full article

We report the synthesis of a gallium complex incorporating redox-active pyridyl nitroxide ligands. The (pyNO⁻)₂GaCl complex was prepared in 85% yield via a salt metathesis route and was characterized by ¹H and ¹³C NMR spectroscopies, X-ray diffraction, and theory. UV–Vis absorption spectroscopy and electrochemistry were used to access the optical and electrochemical properties of the complex, respectively. Our discussion focuses primarily on a comparison of the gallium complex to the corresponding aluminum derivative and shows that although the complexes are very similar, small differences in the electronic structure of the complexes can be correlated to the identity of the metal. Full article

Ferromagnetic cluster spin wave theory (FCSWT) provides an exact and concise description of the low-energy excitations from the ferromagnetic ground state in finite magnetic systems, such as bounded magnetic molecules. In particular, this theory is applicable to the description of experimental inelastic neutron scattering (INS) spectra at low temperatures. We provide a detailed conceptual overview of the FCSWT. Additionally, we introduce a pictorial representation of calculated wavefunctions, similar to the usual depiction of vibrational normal modes in molecules. We argue that this representation leads to a better intuitive understanding of the excitations, their symmetry properties, and has links to the energy and wavevector dependence of intensity in the neutron scattering experiments. We apply FCSWT and illustrate the results on a series of examples with available low-temperature INS data, ranging from the Mn₁₀ supertetrahedron, the Mn₇ disk to the Mn₆ single molecule magnet. Full article

o-Quinones are both well-studied and promising redox-active chelating ligands. There are plenty of interesting effects to be found on o-quinone-derived metallocomplexes, such as photo-thermo mechanical effect in solid phase and in solution, luminescence, SMM properties and so on. A combination o-quinone function with an additional coordination site or redox active fragment in the same molecule might sufficiently extend an assembling as well as functional capability of such ligand in complexes. In this paper, the authors focus on o-quinones decorated with additional non-dioxolene chelating coordination site or with electron donor redox active annelated fragments. Full article

Treatment of N,N′-diisopropylcarbodiimide with sodium cyclopentadienide (NaCp) in a molar ratio of 1:1 in THF solution resulted in formation of the unexpected dinuclear sodium half-sandwich complex [NaC₅H₃{C(NHⁱPr)(=NⁱPr)}₂-1,2]₂ (1) as colorless crystals in low yield. The newly formed ligand, which belongs to the group of 6-aminofulvene-2-aldiminate ligands, coordinates to sodium in an η⁵-coordination mode via the cyclopentadienyl ring. Dimerization occurs through additional chelating κN,N′-coordination of the amidine substituents. The NMR data of 1 indicated a slow dimer/monomer equilibrium in solution. A serendipitously isolated hydrolysis product, {µ-(ⁱPrNH)₂C=O}₂[NaC₅H₃{C(NHⁱPr)(=NⁱPr)}₂-1,2]₂ (2), contains the new 6-aminofulvene-2-aldiminate ligand in the N,N′-chelating coordination mode with the cyclopentadiene ring being uncoordinated. In this case, dimerization occurs through the presence of two bridging neutral N,N′-diisopropylurea ligands. Both compounds have been structurally characterized by single-crystal X-ray diffraction. Full article

Lithium fluoride is an important material for ultraviolet optical systems, possessing among the largest optical bandgaps of dielectric materials. We report on the development of an atomic layer deposition (ALD) process for lithium fluoride that is capable of depositing thin films in a self-limiting manner, with an approximate deposition rate of approximately 0.15 Å per ALD cycle at a substrate temperature of 150 °C. Films are characterized by spectroscopic ellipsometry, atomic force microscopy, X-ray photoelectron spectroscopy, and far ultraviolet reflectometry. For substrate temperatures of 150 °C and greater, films showed significant microroughness with a correlated reduction in effective refractive index. This behavior was mitigated by a reduction in substrate temperature to as low as 100 °C. Films deposited on silicon substrates were subjected to long-term storage testing to evaluate the environmental sensitivity of the deposited layers. Protected aluminum mirrors were also fabricated with ALD LiF overcoats, yielding a reflectance of 84% at a wavelength of 125 nm. The performance relative to state-of-the-art LiF thin films deposited by physical vapor deposition methods is discussed, along with the prospects for future optimization. Full article

The reaction between the 2,2′-benzene-1,4-diylbis(6-hydroxy-4,7-di-tert-butyl-1,3-benzodithiol-2-ylium-5-olate biradical triad (L) and the metallo-precursor [Dy(hfac)₃]·2H₂O leads to the formation of a one-dimensional coordination polymer with the formula {[Dy(hfac)₃(L)]·2C₆H₁₄}_n (1). The X-ray structure reveals that the polymeric structure is formed by the bridging of the Dy(hfac)₃ units with the multi-redox triad L. Single-crystal X-ray diffraction and UltraViolet-visible absorption spectroscopy confirm that the triad L in 1 is bound as a direduced, diprotonated form of o-quinone-extended tetrathiafulvalene-o-quinone (Q-exTTF-Q). Alternate Current (AC) measurements highlight a field-induced single-molecule magnet (SMM) behavior with an energy barrier of 20 K, and thus 1 can be described as a one-dimensional assembly of mononuclear SMMs bridged by the L triad. Full article

A redox-active M₂L₂ metalla-macrocycle is depicted, of which construction has been achieved through coordination driven self-assembly from an electron-rich 9-(1,3-dithiol-2-ylidene)fluorene bis-pyridyl ligand and a cis-blocked square planar palladium complex (Pd(dppf)OTf₂, dppf = 1,1′-Bis(diphenylphosphino)ferrocene). The resulting metalla-macrocycle has been fully characterized in solution, as well as in the solid state (X-ray crystal structure). Its electronic properties show that both constitutive ligands can be oxidized independently through a one-electron process. Full article

A series of metal (Hg, Pt, Ru) bis(alkynyl-tetrathiafulvalene) complexes have been investigated to study the electronic interplay between the metal and the tetrathiafulvalene (TTF), as well as between the two peripheral TTF electrophores along the organometallic bridge. Cyclic voltammetry experiments, together with spectro-electrochemical investigations, have shown the electronic effect of the metal center through the linker on redox properties of the TTF, as well as the influence of the length of the conjugated organic linker. These data show that the degree of coupling can be modulated from no coupling with mercury to appreciable electronic coupling between different electrophores with ruthenium. Full article

In this review we cover some aspects of metal–salophen and metal–salen complex chemistry related to their supramolecular attitude. We examined under the lens of the non-covalent interactions their potential to behave as building blocks for auto-assembled architectures, supramolecular receptors and catalysts, although this last point has been only briefly mentioned. Full article

Sillén–Aurivillius perovskite Bi₄NbO₈X (X = Cl, Br) is a promising photocatalyst for water splitting under visible light, as well as a potential ferroelectric material. In this work, we investigate the crystal growth conditions by mainly varying soak temperature, soak time and cooling rate. Under the optimal conditions, we successfully obtained yellow platelet single crystals with an in-plane distance of several hundred microns. As opposed to conventional crystal growth, a moderate cooling is essential to suppress an evaporation of the Bi–O–Cl species from a melt zone. The single crystals of Bi₄NbO₈Br were also grown using a similar condition. We suggest that the knowledge obtained in this study can be generally applied to other Sillén–Aurivillius phases and related oxyhalides. Full article

A systematic investigation of four heteroleptic bis(diimine) copper(I) dyes in n-type Dye-Sensitized Solar Cells (DSSCs) is presented. The dyes are assembled using a stepwise, on-surface assembly. The dyes contain a phosphonic acid-functionalized 2,2′-bipyridine (bpy) anchoring domain (5) and ancillary bpy ligands that bear peripheral phenyl (1), 4-methoxyphenyl (2), 3,5-dimethoxyphenyl (3), or 3,4,5-trimethoxyphenyl (4) substituents. In masked DSSCs, the best overall photoconversion efficiency was obtained with the dye [Cu(5)(4)]⁺ (1.96% versus 5.79% for N719). Values of J_SC for both [Cu(5)(2)]⁺ (in which the 4-MeO group is electron releasing) and [Cu(5)(4)]⁺ (which combines electron-releasing and electron-withdrawing effects of the 4- and 3,5-substituents) and are enhanced with respect to [Cu(5)(1)]⁺. DSSCs with [Cu(5)(3)]⁺ show the lowest J_SC. Solid-state absorption spectra and external quantum efficiency spectra reveal that [Cu(5)(4)]⁺ benefits from an extended spectral range at higher energies. Values of V_OC are in the order [Cu(5)(4)]⁺ > [Cu(5)(1)]⁺ > [Cu(5)(2)]⁺ > [Cu(5)(3)]⁺. Density functional theory calculations suggest that methoxyphenyl character in MOs within the HOMO manifold in [Cu(5)(2)]⁺ and [Cu(5)(4)]⁺ may contribute to the enhanced performances of these dyes with respect to [Cu(5)(1)]⁺. Full article

The development of a sustainable economy based on the use of renewable resources and the reduction of greenhouse gases emissions is an important mandate in modern societies to minimize the global warming. The CO₂-reforming of methane through a conversion of CO₂ and CH₄ to syngas is a suitable process for this purpose and there is growing interest in the development of new catalysts for this process’ application at an industrial scale. This study is the first to investigate methane dry reforming activity of nickel supported on CeO₂ and CeO₂–ZrO₂ solid solutions doped with neodymium. The supports were synthesized using a surfactant-assisted co-precipitation method and characterized through several analytical techniques to understand the role of synthesis parameters in the distribution of the dopant as well as in the properties of the supports. Co-doping with Zr and Nd resulted in an enhancement of dry reforming activity of ceria due to a higher dispersion of Ni and changes in the strength of basic sites. It was also shown that the addition of Nd helped to mitigate coking issues by increasing the mobility of surface oxygen in ceria and ceria–zirconia oxides and, accordingly, the rate of oxidation of carbonaceous deposits. Full article

The preparation of NaLnF₄ complexes, LnF₃ (Ln = La, Ce, Y) rare earth binary fluorides, CaF₂ and SrF₂ alkali earth fluorides, as well as mixtures of these compounds from their nitrates dissolved in molten NaNO₃ has been studied in order to select the ideal solvent for fluoride synthesis by spontaneous crystallization from flux. Sodium fluoride (NaF) was used as a fluorinating agent. The results of our experiments have confirmed that NaNO₃ melt is one of the most promising media for precipitating said inorganic fluoride materials within a broad temperature range (300–500 °С). Also, in contrast with precipitation/co-precipitation from aqueous solutions, our syntheses have resulted in obtaining equilibrium phases only. Full article

Molecular orientation of dyes must be one of the important factors for designing dye-sensitized solar cells (DSSC). As model systems, we have prepared new hybrid materials composed of azobenzene (AZ) and chiral Schiff base Cu(II) complexes (pn(S)Cu and pn(R)Cu) in polymethyl methacrylate (PMMA) cast films. In addition to experimental results, in order to understand their behavior due to anisotropic alignment of them by linearly polarized UV light irradiation, the so-called Weigert effect, we treated theoretically and discussed based on computational chemistry and mathematical treatments (MD simulation and Bayesian statistics). Full article

Three isostructural cyano-bridged 3d–4f linear heterotrinuclear compounds, (H_2.5O)₄{Ln[TM(CN)₅(CNH_0.5)]₂(HMPA)₄} (Ln = Y^III, TM = [Fe^III]_LS (1); Ln = Dy^III, TM = [Fe^III]_LS (2); Ln = Dy^III, TM = Co^III (3)), have been synthesized and characterized by single-crystal X-ray diffraction. Due to the steric effect of the HMPA ligands, the central lanthanide ions in these compounds possess a low coordination number, six-coordinate, exhibiting a coordination geometry of an axially elongated octahedron with a perfect D_4h symmetry. Four HMPA ligands situate in the equatorial plane around the central lanthanide ions, and two [TM(CN)₅(CNH_0.5)]^2.5− entities occupy the apical positions to form a cyano-bridged 3d–4f linear heterotrinuclear structure. The static magnetic analysis of the three compounds indicated a paramagnetic behavior of compounds 1 and 3, and possible small magnetic interactions between the intramolecular Dy^III and [Fe^III]_LS ions in compound 2. Under zero dc field, the ac magnetic measurements on 2 and 3 revealed the in-phase component (χ′) of the ac susceptibility without frequency dependence and silent out-of-phase component (χ″), which was attributed to the QTM effect induced by the coordination geometry of an axially elongated octahedron for the Dy^III ion. Even under a 1 kOe applied dc field, the χ″ components of 2 were revealed frequency dependence without peaks above 2 K. And under a 2 kOe and 3 kOe dc field, the χ″ components of 3 exhibited weak frequency dependence below 4 K with the absence of well-shaped peaks, which confirmed the poor single-ion magnetic relaxation behavior of the six-coordinate Dy^III ion excluding any influence from the neighboring [Fe^III]_LS ions as that in the analogue 2. Full article