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Two mononuclear trigonal prismatic Co(II) complexes [Co(tppm*)][BPh4]2 (1) and [Co(hpy)][BPh4]2·3CH2Cl2 (2) (tppm* = 6,6′,6″-(methoxymethanetriyl)tris(2-(1H-pyrazol-1-yl)pyridine; hpy = tris(2,2′-b...

Summary Trifluoromethylation has been used for nonfullerene acceptors, resulting in an ultra-narrow band-gap molecule named BTIC-CF3-γ. Compared to its fluorinated and chlorinated analogs, BTIC-CF3-γ possesses the most red-shifted absorptions. The single-crystal structure of BTIC-CF3-γ reveals that the cooperated π-π interactions from H aggregations of central fused cores and J aggregations of end groups lead to a three-dimensional (3D) interpenetrating network, which provides more electron-hopping junctions between different acceptor molecules. After blending with PBDB-TF, a champion power conversion efficiency (PCE) of 15.59% is realized, which is the highest value in reported ultra-narrow band-gap acceptors. Notably, a PCE of 16.50% is also achieved in BTIC-CF3-γ-based ternary devices due to their red-shifted absorptions. Overall, our results provide a visualized understanding of molecule packings of this family of acceptors and also demonstrate that trifluoromethylation is a useful strategy to design highly efficient ultra-low band-gap acceptors for the next nonfullerene solar devices.

Three cyanide-bridged {Fe2Fe} complexes of formula {[(TpR)Fe(CN)3]2[Fe(bnbpen)]}·S (TpR = Tp for 1·S, Tp3−Me for 2·S, and Tp* for 3·S, respectively; bnbpen = N,N′-bis-(2-naphthylmethyl)-N,N′-bis(2-picolyl)-ethylenediamine) have been prepared and characterized here. Single-crystal X-ray diffraction analysis revealed that all compounds feature right angled trinuclear structures with two [(TpR)Fe(CN)3]− units at the ends and one [Fe(bnbpen)]2+ at the centre. Besides the rich hydrogen bonds, remarkable π–π interactions are evidenced in all compounds between the intermolecular naphthyl and pyrazolyl rings. As a result, compounds 1·S and 2·S exhibit irreversible two-step and one-step spin-transitions, respectively, during the process of removing solvents, with T1/2 at 314 K and 376 K for 1·S and 350 K for 2·S, while compound 3·S shows a reversible one-step spin transition at relatively lower temperatures with T1/2 = 250 K, and what's more, an irreversible small magnetic change accompanied by the loss of lattice solvents was observed. The solvent-free compounds show SCO properties at lower temperatures than the corresponding solvated ones; however, the solvent-free compound 1 maintains an unexpected high-spin state and does not follow the trend that their transition temperatures decrease with the enhancement of the electron donor properties of the TpR ligands (Tp* < Tp3−Me < Tp), likely due to the more compact π–π stacking mode in comparison with those for compounds 2·S and 3·S.

To elevate the performance of polymer solar cells (PSC) processed by non-halogenated solvents, a dissymmetric fused-ring acceptor BTIC-2Cl-γCF3 with chlorine and trifluoromethyl end groups has been designed and synthesized. X-ray crystallographic data suggests that BTIC-2Cl-γCF3 has a 3D network packing structure as a result of H- and J-aggregations between adjacent molecules, which will strengthen its charge transport as an acceptor material. When PBDB-TF was used as a donor, the toluene-processed binary device realized a high power conversion efficiency (PCE) of 16.31 %, which improved to 17.12 % when PC71ThBM was added as the third component. Its efficiency of over 17 % is currently the highest among polymer solar cells processed by non-halogenated solvents. Compared to its symmetric counterparts BTIC-4Cl and BTIC-CF3 -γ, the dissymmetric BTIC-2Cl-γCF3 integrates their merits, and has optimized the molecular aggregations with excellent storage and photo-stability, and also extending the maximum absorption peak in film to 852 nm. The devices exhibit good transparency indicating a potential utilization in semi-transparent building integrated photovoltaics (ST-BIPV).

Treatment of CoCl2·6H2O and tris(pyrazolyl-1-yl)borate tricyanoiron(III) anions at 55 °C afforded a series of new Fe-Co polynuclear clusters: {Co2Cl2(DMF)4[(Tp4-Me)Fe(CN)3]2} (1; Tp4-Me = hydridotr...

A new octacyanotungstate(V) based single chain magnet {[(Tpm)Co(DMF)W(CN)8]2[Co(DMF)4]·2DMF}n (1, Tpm = 1,1,1-trispyrazoylmethane), with an effective barrier of 39.7(3) cm−1 is reported. The Ising-like magnetic anisotropy of the chain originates from the nearly parallel local orientations of the Co(II) ions with the source of the uniaxial magnetic anisotropy being a trigonal distortion of the octahedral environment with the fac-tridentate capping Tpm ligand.

A linear trinuclear ferrous complex [FeII3(pymp)4(MeOH)2][BPh4]2·2MeOH (1) (Hpymp = 2-[(pyridine-2-ylimine)-methyl]phenol) was isolated and characterized both structurally and magnetically. A magnetic study revealed the ferromagnetic coupling (J = +3.54 cm-1) within the [FeII3] units and uniaxial magnetic anisotropy (D = -1.21 cm-1) of the molecule. Slow relaxation of the magnetization at below 5 K and an effective energy barrier of 26.0(2) cm-1 under a 1200 Oe applied dc field were evidenced. Moreover, clear magnetic hysteresis loops were observed at below 2.5 K, which further corroborated the single-molecule magnet behavior of 1.

Hydrothermal reactions of copper(II) and cobalt(II) salts with 1-tetrazole-phenyl-4-methylphosphonic acid yielded the coordination polymers [Cu(H 2 O)(HO 3 PCH 2 C 6 H 4 CN 4 )]·H 2 O ( 1 ·H 2 O) and [Co(H 2 O) 2 (HO 3 PCH 2 C 6 H 4 CN 4 H) 2 ]·2H 2 O ( 2 ·2H 2 O). Compound 1 ·H 2 O is two dimensional and is constructed from chains of trans -corner sharing, ‘4+2’ axially distorted {CuO 4 N 2 } octahedra. These chains are linked through the organic tethers of the ligands in the doubly deprotonated form{HO 3 PCH 2 C 6 H 4 CN 4 } 2− to propagate in two-dimensions. In contrast, compound 2 ·2H 2 O is one-dimensional and features {CoO 4 N 2 } octahedra linked through pairs of ligands in the singly deprotonated form {HO 3 PCH 2 C 6 H 4 CN 4 H} −1 , i.e. with the tetrazole terminus in the neutral form. The magnetic properties of compound 1 ·H 2 O reflect the structure where the Cu(II) ions are bridged by syn-syn phosphate and tetrazolate Cu-N-N-Cu bridges, with the former linkage likely to transfer ferromagnetic coupling whereas the latter leads to antiferromagnetic coupling. The two competing pathways lead to negligible overall coupling.

The preparation, structures, and spectroscopic properties of several molecular complexes and a one dimensional chain are described. A one-dimensional {trans-CrII(DMF)2(OTs)2}n (1) chain and mononuclear complexes of trans-[MII(OTs)2(DMF)4] (MII = Fe, 2; Co, 3) and [NiII(DMF)6][OTs]2 (4) stoichiometry are readily obtained from DMF/Et2O solutions containing the parent anhydrous tosylate salts. A hydrated analogue, trans-[FeII(OTs)2(OH2)2(DMF)2] (5), is obtained in minor quantities from solutions containing 2. Electronic spectra indicate all of the complexes adopt octahedral geometries in dimethylformamide solution. Room temperature susceptibility data indicates that high spin electronic configurations are preferred for 1 (S = 2), 2 (S = 2), and 3 (S = 3/2) while 4 adopts an S = 1 spin ground state. The solubility properties of the salts are also described.

The design of coordination sites around lanthanide ions has a strong impact on the sensitization of their luminescent signal. An imidodiphosphonate anionic binding site is attractive as it can be functionalized with "remote" sensitizer units, such as phenoxy moieties, namely, HtpOp, accompanied by an increased distance of the lanthanide from the ligand high-energy stretching vibrations which quench the luminescence signal, hence providing flexible shielding of the lanthanide. We report the formation and isolation of Ln(tpOp)3 complexes where Ln = Er, Gd, Tb, Dy, Eu, and Yb and the Y(tpOp)3 diamagnetic analogue. The complexes are formed from reaction of KtpOp and the corresponding LnCl3·6H2O salt either by titration and in situ formation or by mixing and isolation. All complexes are seven-coordinated by three tpOp ligand plus one ethanol molecule, except for Yb(tpOp)3 which has no solvent coordinated. Phosphorus NMR shows characteristic shifts to support the coordination of the lanthanide complexes. The complexes display visible and near-infrared luminescence with long lifetimes even for the near-infrared complexes which range from 3.3 μs for Nd(tpOp)3 to 20 μs for Yb(tpOp)3. The ligand shows more efficient sensitization than the imidodiphosphinate analogues for all lanthanide complexes with a notable quantum yield of the Tb(tpOp)3 complex at 45%. We attribute this to the properties of the remote sensitizer unit and its positioning further away from the lanthanide, eliminating quenching of high energy C-H vibrations from the ligand shell. Calculations of the ligand shielding support the photophysical properties of the complexes. These results suggest that these binding sites are promising in the further development of the lanthanide complexes in optoelectronic devices for telecommunications and new light emitting materials.

Three mononuclear metal complexes [MII(L-N3O2)(MeCN)2][BPh4]2 (M = Fe, 1; Co, 2; Ni, 3) were isolated and structurally characterized. Magnetic studies revealed uniaxial magnetic anisotropy for 1 (D = −17.1 cm−1) and 3 (D = −14.3 cm−1) and easy-plane magnetic anisotropy for 2 (D = +36.9 cm−1). Slow magnetic relaxation was observed for complexes 1 and 2 under an applied magnetic field, both of which are dominated by a Raman process.

A new tripodal hexadentate ligand of tris[6-(1 H-pyrazol-1-yl)pyridin-2-yl]methanol (tppm) was synthesized and explored for constructing the trigonal-prismatic cobalt(II) complex [Co(tppm)][ClO4]2·2CH3CN·H2O (1). Magnetic study showed that 1 exhibited large uniaxial magnetic anisotropy with a zero-field-splitting parameter of -80.7 cm-1 and typical single-molecule-magnet behavior.

The preparation, structures, and magnetic properties of two tricyanoferrates, [NEt4]2[(Tp*Me)FeII(CN)3]·MeCN (1) and [NEt4][(Tp*Me)FeIII(CN)3]·H2O (2), and three trinuclear derivatives, {[(Tp*Me)FeIII(CN)3]2[NiII(L)2]}·n(solvent) (L = bpy, 3; tren, 4; DETA, 5) are described. Magnetic measurements show that 2 is an S = 1/2 complex [g = 2.65(1)], while 3–5 display ST = 2 spin ground states, owing to cyanide-mediated ferromagnetic exchange between FeIIILS (S = 1/2) and NiII (S = 1) ions. The χT vs. T data for 3–5 were modelled using an isotropic Heisenberg model and give J/kB and gavg values of +11.1(1) K and 2.48(1) for 3, 9.1(1) K and 2.6(1) for 4, and +11.2(1) K and 2.41(5) for 5 (with zJ′ = –0.28 K). High-field/frequency EPR data indicates significant g-anisotropy in 2 (gz = 3.6, gy = 2.2, gx = 2.0) and [NEt4][(Tp*)FeIII(CN)3]·H2O (6) (gz = 3.5, gy = 2.0, gx = 1.3), while 5 shows D = –2.09 cm–1, E = 0.08 cm–1, and B40 = –2.3 × 10–3 cm–1 with gz = 2.4 and gx = gy = 1.95. Despite significant magnetic anisotropy in 3–5, frequency-dependent behavior is only seen for 5 above 1.8 K, suggesting that rapid quantum tunnelling of the magnetization is operative.

The air-stable mononuclear Co(II) compounds [CoII(Tpm)2][ClO4]2 (1, Tpm = tris(pyrazol-1-yl)methane), [CoII(Tpm)2][BPh4]2·2MeCN (2) with trigonal antiprismatic geometry (trigonally elongated octahedral geometry) are reported. Magnetic and theoretical studies reveal that the complexes exhibit single-molecule magnet behavior with uniaxial anisotropy and a huge energy difference between ground and first excited Karmers' doublets (∼200 cm−1). Under applied DC fields, compounds 1 and 2 exhibit frequency and temperature dependence of the imaginary susceptibility. The fit of the data to an Orbach relaxation process yields effective energy barriers of 30.6(1) and 44.7(6) cm−1 for 1 and 2, respectively, but there is no real state at that energy. The inclusion of tunneling, direct and Raman relaxation processes leads to the conclusion that the inclusion of an Orbach process is not required to provide a good fit to the data. More interestingly, a detailed study of the dependence of the relaxation time with field shows that for these Kramers' ions, tunneling is the predominant process at low temperature and that differences in the counteranion allow for a tuning of the Raman process at higher temperatures. These findings underscore the fact that large uniaxial anisotropy can be achieved in hexacoordinate Co(II) trigonal antiprismatic complexes which is an unexplored geometry in mononuclear single molecule magnets.

The preparation, structure, and magnetic properties of a one-dimensional chain, {[(pzTp)FeIII(CN)3][MnII(phen)2][ClO4]}n (1), are described. It is readily obtained from methanolic solutions containing [NEt4][(pzTp)FeIII(CN)3]·H2O, MnII(ClO4)·6H2O, and two equivalents of 9,10-phenanthroline. Magnetic data indicate that the low spin FeIIILS (S = ½) and high spin MnIIHS (S = 5/2) ions experience weak cyanide-mediated antiferromagnetic exchange [Jiso = −0.92(1) cm−1 and giso = 2.06(2)] owing to the presence of highly distorted FeIII(μ-CN)MnII units.

Dynamic molecular crystals are of high interest due to their potential applications. Herein we report the reversible on–off switching of single-molecule magnet (SMM) behavior in a [Mo(CN)7]4– based molecular compound. Upon dehydration and rehydration, the trinuclear Mn2Mo molecule [Mn(L)(H2O)]2[Mo(CN)7]·2H2O (1) undergoes reversible crystal-to-crystal transformation to a hexanuclear Mn4Mo2 compound [Mn(L)(H2O)]2[Mn(L)]2[Mo(CN)7]2 (2). This structural transformation involves the breaking and reforming of coordination bonds which leads to significant changes in the color and magnetic properties. Compound 1 is an SMM with an energy barrier of 44.9 cm–1, whereas 2 behaves as a simple paramagnet despite its higher ground state spin value. The distortion of the pentagonal bipyramidal geometry of [Mo(CN)7]4– in 2 disrupts the anisotropic exchange interactions that lead to SMM behavior in 1.

A computational study and magnetic susceptibility measurements of three homonuclear Fe(III) Keggin structures are herein presented: the [FeO4@Fe12F24(μ−OCH3)12]5− anion (1), the [Bi6{FeO4@Fe12O12(OH)12}(μ-O2CCCl3)12]+ cation (2) and its polymorph [Bi6

Reaction of [NEt 4 ][(pzTp)Fe III (CN) 3 ], nickel(II) trifluoromethanesulfonate and 4,4,5,5-tetramethylimidazoline-1-oxyl-2-(2′-pyridyl) (IM-2Py) affords {[(pzTp)Fe III (CN) 3 ] 2 Ni II (IM-2Py) 2 }·2DMF·H 2 O·0.5Et 2 O ( 1 ) as a bent cyanide-bridged trinuclear complex. As judged from simulations of the magnetic data, the magnetic exchange between the {Fe III 2 Ni II } ( S = 2) and both IM-2Py ( S = ½) radical ligands are negligible, or in other words, each radical imparts a Curie contribution to the overall paramagnetism of the complex; the best set of parameters are g iso = 2.53(5), g rad = 2 (fixed), and J iso / k B = 3.9(1) K. ac susceptibility and M versus H data show that 1 does not exhibit slow relaxation of the magnetization above 1.8 K. Consistent with the magnetic data, we conclude that bent cyanide bridges, an improper alignment of the Fe III LS anisotropy tensors, and/or small IM-2Py ring distortions conspire to bring insufficient magnetic anisotropy to the complex, and prevent observation of single-molecule magnet behavior.

4 pages; International audience; Flip to be square: Structural, spectroscopic, magnetic, and photomagnetic studies conclusively demonstrate that a tetranuclear cyanometalate {Fe2Co2} complex undergoes reversible thermally and light-induced changes in optical and magnetic properties. This instability is induced by an intramolecular electron transfer, as oberved in three-dimensional Co/Fe Prussian blue compounds (see picture).

7 pages; International audience; Treatment of [NEt4][(Tp⁄Me)FeIII(CN)3].H2O with nickel(II) trifluoromethanesulfonate affords {[(Tp⁄Me)- FeIII(CN)3]2[NiII(DMF)4]2[OTf]2}.2DMF (1) while {[(Tp⁄Me)FeIII(CN)3]2[NiII(bpy)2]2[ClO4]2}.3MeCN=2H2- O.MeOH (2) is obtained from Ni(ClO4)2.6H2O and 2,20-bipyridine mixtures. In the frame of an isotropic Heisenberg model, the experimental vT versus T data were modeled well with the following best set of parameters: J/kB = +9.0(4) and +8.5(4) K and gav = 2.4(1) and 2.5(1) for 1 and 2, respectively; the first excited state (S = 2) for 1 and 2 are ca. 18 and 16.8 K above the ST = 3 ground state. Analysis of the ac susceptibility suggests that 1 exhibits fast quantum tunneling of the magnetization above ca. 1.8 K while 2 displays slow relaxation in the range seen for many SMMs; at Hdc = 2.2 kOe an SMM energy barrier of Deff = 15.7 K is estimated for 2. Upon prolonged standing in air, 1 is readily transformed into a new system that exhibits a respectable energy barrier (Deff = 20.4 K) suggesting that the desolvation is able to dramatically alter the dynamics and the quantum properties of the square-shaped {FeIII2(l-CN)4NiII 2}SMM.

The syntheses, structures, and magnetic properties of a series of di- and trivalent hydridotris(3,5-dimethylpyrazol-1-yl)borate (Tp*) cyanomanganates are described. Treatment of tris(acetylacetonate)manganese(III) [Mn(acac)(3)] with KTp* and tetra(ethyl)ammonium cyanide affords [NEt(4)][(Tp*)Mn(II)(κ(2)-acac)(CN)] (1), as the first monocyanomanganate(II) complex; attempted oxidation of 1 with iodine affords {(Tp*)Mn(II)(κ(2)-acac(3-CN))}(n) (2) as a one-dimensional chain and bimetallic {[NEt(4)][(Tp*)Mn(II)(κ(2)-acac(3-CN))](2)(μ-CN) (3) as the major and minor products, respectively. A fourth complex, [NEt(4)][(Tp*)Mn(II)(η(2)-acac(3-CN))(η(1)-NC-acac)] (4), is obtained via treatment of Mn(acac(3-CN))(3) with KTp* and [NEt(4)]CN, while [NEt(4)](2)[Mn(II)(CN)(4)] (5) was prepared from manganese(II) trifluoromethanesulfonate and excess [NEt(4)]CN. Tricyanomanganate(III) complexes, [cat][(Tp*)Mn(III)(CN)(3)] [cat = NEt(4)(+), 7; PPN(+), 8], are prepared via sequential treatment of Mn(acac(3-CN))(3) with KTp*, followed by [NEt(4)]CN, or [cat](3)[Mn(III)(CN)(6)] with (Tp*)SnBu(2)Cl. Magnetic measurements indicate that 1, 2, and 4 contain isotropic Mn(II) (S = (5)/(2); g = 2.00) centers, and no long-range magnetic ordering is found above 1.8 K. Compounds 7 and 8 contain S = 1 Mn(III) centers that adopt singly degenerate spin ground states without orbital contributions to their magnetic moments.

3 pages; International audience; A new tricyanoferrate(III) building block and a trinuclear single-molecule magnet derivative are described. The treatment of a 2:1 ratio of [NEt4][(Tp*Bn)FeIII- (CN)3] 3H2O3MeOH [1; Tp*Bn = tris(3,5-dimethyl-4- benzyl)pyrazolylborate] with nickel(II) trifluoromethanesulfonate gives {[(Tp*Bn)FeIII(CN)3]2[NiII(DMF)4]} 3 2DMF (2; DMF = N,N-dimethylformamide). The symmetryequivalent FeIII LS ions lead to a favorable alignment of anisotropy tensors (i.e., Fe 3 3 3B axes) in 2, and an energy barrier of Δeff/kB = 16.7 K is found for the ST = 2 complex.

3 pages; International audience; A new low symmetry octanuclear cyano-based {FeIII 4NiII4} single-molecule magnet (SMM) is described. This SMM exhibits the highest energy barrier (D/kB E 33 K) for magnetization reversal seen for any first-row cyanide-based complex. The importance of anisotropy axes alignment and their impact on SMM properties are illustrated when cubic {FeIII 4NiII4} boxes are compared to octanuclear complexes of lower overall symmetry.

3 pages; International audience; Two cyano-bridged single-molecule magnets of {FeIII 4NiII2} and {FeIII 6NiII 3} stoichiometry are described via their magnetic properties described in the frame of geometrical core distortions and orientations of their local anisotropy axes.

The recent years have witnessed the glory development for the construction of high-performance mononuclear single molecule magnets (SMMs) within a specific coordination geometry, which, however, is not well applied in cluster-based SMMs due to the synthetic challenges. Given that the monocobalt(II) complexes within a trigonal-prismatic (TPR) coordination geometry have been classified as excellent SMMs with huge axial anisotropy (D ≈ -100 cm-1), here we designed and synthesized a new dual-capping tetrazine ligand, 3,6-bis(6-(di(1H-pyrazol-1-yl)methyl)pyridin-2-yl)-1,2,4,5-tetrazine (bpptz), and prepared a novel dicobalt(II) complex, [Cp2CoIII][{(hfac)CoII}2(bpptz•-)][hfac]2·2Et2O (1, hfac = hexafluoroacetylacetonate). In the structure of 1, the bpptz•- radical ligand enwraps two Co(II) centers within quasi-TPR geometries, which are further bridged by the tetrazine radical in the trans mode. The magnetic study revealed that the interaction between the Co centers and the tetrazine radical is strongly antiferromagnetic with a coupling constant (J) of -65.8 cm-1 (in the -2J formalism). Remarkably, 1 exhibited the typical SMM behavior with an effective energy barrier of 69 cm-1 under a 1.5 kOe dc field, among the largest for polynuclear transition metal SMMs. In addition, DFT and ab initio calculations suggested that the presence of a strong Co(II)-radical magnetic interaction effectively quenches the QTM effect and enhances the barrier height for the magnetization reversal.