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The combined use of 2-(2-pyridyl)-1,3-propane-diol (pypdH2) and 2-hydroxymethyl-2-(2-pyridyl)-1,3-propane-diol (pyptH3) in Cu2+/4f chemistry has afforded a new family of isostructural [Cu6M4(pypt)4(pypdH)4(NO3)8] [M = Gd (1), Tb (2), Dy (3), and Y (4)] complexes. These compounds are based on an unprecedented three-layered symmetric [Cu6M4(μ-OR)16]8+ structural core, formed from the connection of the metal ions by bridging alkoxide arms of the organic ligands. Direct current magnetic susceptibility studies for complexes 1–3 revealed the presence of dominant ferromagnetic exchange interactions, suggesting the existence of large spin ground state values. Alternating current magnetic studies indicate the presence of slow-magnetic relaxation in 1–3. [ABSTRACT FROM AUTHOR]

In the course of an investigation of the supramolecular behaviour of copper(II) complexes with the 5‐phenylimidazole/perchlorate ligand system ('blend') remarkable solvatomorphism has been observed. By employing a variety of crystallization solvents (polar protic, polar/non‐polar aprotic), a series of 12 crystalline solvatomorphs with the general formula [Cu(ClO4)2(LH)4]·x(solvent) have been obtained [LH = 5‐phenylimidazole, x(solvent) = 3.3(H2O) (1), 2(methanol) (2), 2(ethanol) (3), 2(1‐propanol) (4), 2(2‐propanol) (5), 2(2‐butanol) (6), 2(dimethylformamide) (7), 2(acetone) (8), 2(tetrahydrofurane) (9), 2(1,4‐dioxane) (10), 2(ethyl acetate) (11) and 1(diethyl ether) (12)]. The structures have been solved using single‐crystal X‐ray diffraction and the complexes were characterized by thermal analysis and infrared spectroscopy. The solvatomorphs are isostructural (triclinic, P1), with the exception of compound 9 (monoclinic, P21/n). The supramolecular structures and the role of the various solvents is discussed. All potential hydrogen‐bond functionalities, both of the [Cu(ClO4)2(LH)4] units and of the solvents, are utilized in the course of the crystallization process. The supramolecular assembly in all structures is directed by strong recurring Nimidazole–H...Operchlorate motifs leading to robust scaffolds composed of the [Cu(ClO4)2(LH)4] host complexes. The solvents are located in channels and, with the exception of the disordered waters in 1 and the diethyl ether in 12, participate in hydrogen‐bonding formation with the [Cu(ClO4)2(LH)4] complexes, serving as both hydrogen‐bond acceptors and donors (for the polar protic solvents in 2–6), or solely as hydrogen‐bond acceptors (for the polar/non‐polar aprotic solvents in 7–11), linking the complexes and contributing to the stability of the crystalline compounds. [ABSTRACT FROM AUTHOR]

In a search to explore the structural landscape of possible copper(II) complexes with the 4-phenylimidazole/ tetrafluoroborate combination, considerable solvatomorphism has emerged. The utilization of a wide variety of crystallization solvents (polar protic, polar and non-polar aprotic) resulted in a series of seventeen crystalline solvatomorphs with the general formulae [Cu(BF4)2(HL)4]·x(solvent) [HL = 5-phenylimidazole, x(solvent) = 2(acetone)·2(water) (1), 2(methanol) (2), 2(ethanol) (3), 2(1-propanol) (4), 1.4(2-propanol) (5), 2(1-butanol) (6), 2(iso-butanol) (7), 1.33(tert-butanol) (8), 2(1-pentanol) (9), 2(dimethylformamide) (10), 1.2(acetone) (11), 2(tetrahydrofurane) (12), 1.85(1,4-dioxane) (13), 0.86(ethyl acetate) (14), 1(diethyl ether) (15), 0.7(diisopropyl ether) (16), 1(n-hexane) (17)]. A reaction using the CH2Cl2/MeCN solvent system produced crystals of the [Cu(HL)4(MeCN)(H2O)0.4](BF4)2 complex (18). Crystallization with nitromethane yielded [Cu{SiF2O(OMe)}2(HL)4]·0.8MeNO2 (19·0.8MeNO2), due to the in situ reaction of fluoride ions from BF4− ions with the glass surface of the vial used to grow crystals. The structures have been solved by single-crystal X-ray diffraction and the complexes were characterized by thermal analysis and infrared spectroscopy. The crystallization solvents are located in channels, with the exception of 1.33(tert-butanol) (8) and 1.2(acetone) (11) residing in lattice pockets. An analysis to understand the role of the solvents in the molecular self-assembly process is described. Depending on the hydrogen-bond functionalities of each solvent, three distinct cases emerge i) the solvents link neighboring [Cu(BF4)2(HL)4] molecules via N–H⋯Osolvent–H⋯F intermolecular associations (polar protic solvents, compounds 1–9), ii) they are terminally connected to [Cu(BF4)2(HL)4] molecules (polar aprotic solvents, compounds 10–13) and iii) they simply reside in channels without any involvement in supramolecular motifs (non-polar solvents, compounds 14–17). The final crystal packings result from the concerted action of robust N–H⋯F synthons and the above described interactions involving the solvent molecules. [ABSTRACT FROM AUTHOR]

A new family of 2-D 8-connected rare earth (RE) MOFs based on a hexanuclear (RE3+)6 secondary building unit (SBU), the increase of the dimensionality through single-crystal-to-single-crystal (SCSC) linker installation reactions and the turn-on of the temperature sensing capability upon these reactions are reported. The reaction of RE(NO3)3 with 4,4′-(hydroxymethylene)dibenzoic acid (H2BCPM) in the presence of 2-fluorobenzoic acid (HFBA) in DMF/H2O at 115 °C afforded compounds [RE6(μ3-OH−/F−)8(BCPM)4(NO3)2(H2O)4]n (UCY-17(RE); RE: Y, Gd, Tb, Dy, Ho, Er) which represent rare examples of 2D 8-c MOFs based on a hexanuclear (RE3+)6 SBU. The excellent quality of single crystals of UCY-17(Tb) and the distance between the terminal nitrate ions prompted us to investigate the SCSC exchange of NO3− anions by various dicarboxylate ligands aiming to bridge adjacent 2D nanosheets and form 3-D analogues. These SCSC linker installation reactions afforded a series of 3-D, 10-connected mixed linker MOFs with the general formulae [RE6(μ3-OH−/F−)8(BCPM)4(L)(H2O)4]n (UCY-17(Tb)/L; H2L = H2BDC (1,4-benzenedicarboxylic acid), H2ABDC (2-aminobenzene-1,4-dicarboxylic acid), H2FBDC (2-fluorobenzene-1,4-dicarboxylic acid), and H2NDC (1,4-naphthalenedicarboxylic acid)). The exchanged analogues of UCY-17(Gd) and UCY-17(Eu0.05Tb0.95) were synthesized and the thermometric properties of the latter were investigated. These studies revealed that there is no thermal evolution of the emission properties for the pristine MOF UCY-17(Eu0.05Tb0.95) whereas the exchanged analogues exhibit significant thermometric properties at higher temperatures (>270 K). The maximum thermal sensitivity of most exchanged derivatives appears at physiological temperatures and ranges between 300 and 355 K. Overall, this work proposes a promising strategy for increasing the dimensionality of 2-D MOFs and controlling the thermometric performances of mixed Eu0.05Tb0.95 MOFs. [ABSTRACT FROM AUTHOR]

The employment of cyanato (OCN-) group in high oxidation state manganese cluster chemistry, in conjunction with carboxylate ions and the organic chelating/bridging ligand 2-(hydroxymethyl)pyridine (hmpH), is reported. The syntheses, crystal structures, and magnetochemical characterization are described for [Mn16O8(OR)4(OCN)4(O2CMe)12(hmp)6(ROH)2] (R = Me (1), Et (2)) and [Mn18O14(O2CR)18(hmp)4(hmpH)2(H2O)2] (R = Me (3), Et (4)). The 2:1:1:1 reactions of Mn(O2CMe)2·4H2O, hmpH, NaOCN and NEt3 in solvent MeOH or EtOH afford the isostructural complexes [Mn16O8(OR)4(OCN)4(O2CMe)12(hmp)6(ROH)2] (R = Me (1), Et (2)). The [Mn16(μ4-O)4(μ3-O)4(μ-OMe)4(μ3-OR)6(μ-OR)6]10+ core of representative complex 1 comprises a MnII4MnIII4 double-cubane subunit attached on either side to two symmetry-related MnIIMnIII3 defective dicubanes. A similar reaction of Mn(O2CR)2·4H2O, hmpH, NaOCN and NEt3, but in solvent MeCN, led instead to the formation of [Mn18O14(O2CR)18(hmp)4(hmpH)2(H2O)2] (R = Me (3), Et (4)). Compounds 3 and 4 are very similar to each other and can be described as a central [MnIII4(μ-O)6] rodlike subunit attached on either side to two symmetry-related [Mn7O9] subunits. Variable-temperature, solid-state dc and ac magnetic susceptibility studies revealed the presence of predominant antiferromagnetic exchange interactions in all compounds, and possible S = 2 or 1 (for 1 and 2) and S = 0 (for 3 and 4) ground state spin values. The combined results demonstrate the ability of cyanato groups to facilitate the formation of new polynuclear MnII/III complexes with structures different than these obtained from the use of the related azides.

Three new polynuclear clusters with the formulae [Mn10O4(OH)(OMe){(py)2C(O)2}2{(py)2C(OMe)(O)}4(MeCO2)6](ClO4)2 (1), Na[Mn12O2(OH)3(OMe){(py)2C(O)2}6{(py)2C(OH)(O)}2(MeCO2)2(H2O)10](ClO4)8 (2) and [Mn12O4(OH)2{(py)2C(O)2}6{(py)2C(OMe)(O)}(MeCO2)3(NO3)3(H2O)(DMF)2](NO3)2 (3) were prepared from the combination of di‐2‐pyridyl ketone, (py)2CO, with the aliphatic diols (1,3‐propanediol (pdH2) or 1,4‐butanediol (1,4‐bdH2)) in Mn carboxylate chemistry. The reported compounds do not include the aliphatic diols employed in this reaction scheme; however, their use is essential for the formation of 1–3. The crystal structures of 1–3 are based on multilayer cores which, to our knowledge, are reported for the first time in Mn cluster chemistry. Direct current (dc) magnetic susceptibility studies showed the presence of dominant antiferromagnetic exchange interactions within 1–3. Alternating current (ac) magnetic susceptibility studies revealed the presence of out‐of‐phase signals below 3.0 K for 2 and 3 indicating the slow relaxation of the magnetization vector, characteristic of single‐molecule magnets; the Ueff value of 2 was found to be 23 K and the preexponential factor τ0 ~7.6×10−9 s. [ABSTRACT FROM AUTHOR]

Isolation of mixed-ligand compounds has attracted considerable research interest as the synergy between ligands results in species with interesting technological, environmental and biomedical applications. In this study, initial employment of 2-pyridyl oximes or 2-pyridyl alcohols in combination with 2-hydroxyterephthalic acid (H3MHBDC) and 2,5-dihydroxyterephthalic acid (H4DHBDC) has yielded a new family of 1D coordination polymers and a metal cluster, namely [M(H2pyaox)2(H2DHBDC)]n (M = Zn, 1; Mn, 2), [Co3(mpko)4(Hmpko)2](H2DHBDC)2·2DMF (3·2DMF), [M(Hhmp)2(H2DHBDC)]n·DMF (M = Ni, 4·DMF; Zn, 5·DMF), [Ni(H2pyaox)2(HMHBDC)]n·2DMF (6·2DMF), and [Zn(Hmpko)2(HMHBDC)]n·DMF (7·DMF), where H2pyaox = pyridine-2-amidoxime and Hmpko = 2-methyl pyridyl ketoxime. 1–7 are the first compounds bearing a 2-pyridyl oxime or 2-pyridinemethanol (Hhmp) with H3MHBDC or H4DHBDC in their neutral or anionic form. Notably, 4 exhibits a high capacity for Co2+ uptake (900 mg Co2+ g−14), which can be attributed to the presence of free coordination sites in the carboxylate linker. [ABSTRACT FROM AUTHOR]

The initial use of a tetradentate Schiff base (LH2) derived from the 2 : 1 condensation between 2-hydroxyacetophenone and cyclohexane-1,2-diamine in 4f-metal chemistry is described. The 1 : 2 reaction of Ln(NO3)3·xH2O (Ln = lanthanoid or yttrium) and LH2 in MeOH/CH2Cl2 has provided access to isostructural complexes [Ln(NO3)3(L′H2)(MeOH)] in moderate to good yields. Surprisingly, the products contain the corresponding Schiff base ligand L′H2 possessing six aliphatic –CH2– groups instead of the –CH–(CH2)4–CH– unit of the cyclohexane ring, i.e. an unusual ring-opening of the latter has occurred. A mechanism for this LnIII-assisted/promoted LH2 → L′H2 transformation has been proposed assuming transient LnII species and a second LH2 molecule as the H2 source for the reduction of the cyclohexane moiety. DFT calculations provide strong evidence for the great thermodynamic stability of the products in comparison with analogous complexes containing the original intact ligand. The structures of the PrIII, SmIII, GdIII, TbIII, and HoIII complexes have been determined by single-crystal X-ray crystallography. The 9-coordinate LnIII centre in the molecules is bound to six oxygen atoms from the three bidentate chelating nitrato groups, two oxygen atoms that belong to the bidentate chelating organic ligand, and one oxygen atom from the coordinated MeOH group. In the overall neutral bis(zwitterionic) L′H2 ligand, the acidic H atoms are clearly located on the imino nitrogen atoms and this results in the formation of an unusual 16-membered chelating ring. The coordination polyhedra defined by the nine donor atoms around the 4f-metal-ion centres can be best described as distorted, spherical capped square antiprisms. The EuIII, TbIII, and DyIII complexes exhibit LnIII-based luminescence in the visible region, with the coordinated L′H2 molecule acting as the antenna. Ac magnetometry experiments show that the DyIII member of the family behaves as an SIM at zero field and under external dc fields of 0.1 and 0.2 T without the enhancement of the peaks' maxima, suggesting that QTM is not the relaxation path. The GdIII complex behaves, rather unexpectedly, as a SIM with two different magnetic relaxation paths occurring at very close temperatures; this behaviour is tentatively attributed to a very small axial zero-field splitting (D ∼ 0.1 cm−1), which cannot be detected by magnetization or susceptibility experiments. The prospects of the present, first results in the lanthanoid(III)-LH2 chemistry are discussed. [ABSTRACT FROM AUTHOR]

The synthesis, crystal structures, Mössbauer spectra and variable temperature dc and ac magnetic susceptibility studies of a new family of trinuclear heterometallic Fe3+/Ln3+ complexes, [Fe2Ln(PhCO2)3((py)2CO2)((py)2C(OMe)O)2(NO3)Cl] (Ln = Gd (1/Gd), Tb (1/Tb), Dy (1/Dy), and Ho (1/Ho)), where (py)2CO22− and (py)2C(OMe)O− are the anions of the gem-diol and hemiketal derivatives of di-2-pyridyl ketone, are reported. Compounds 1/Ln are based on an asymmetric "V-shaped" [Fe3+(μ-OR)Ln(μ-OR)2Fe3+]6+ structural core formed from the connection of the two terminal Fe3+ centers to the central Ln3+ ion either through one or two alkoxide groups originating from the alkoxide-type bridging ligands. Direct current magnetic susceptibility studies reveal the presence of weak antiferromagnetic interactions between the Fe3+ ions. Alternating current magnetic studies indicate the presence of a slow-magnetic relaxation process in 1/Dy with an energy barrier Ueff = 6.7 (±0.3) K and a pre-exponential factor, τ0 = 2.2 (±0.4) × 10−7 s. The electronic, magnetic and relaxation properties of the complexes were further monitored by variable temperature 57Fe Mössbauer spectroscopy. At T > 80 K the spectra from the complexes comprise two quadrupole doublets the hyperfine parameters of which reflect the distinct coordination environment of the two Fe3+ terminal sites. At T < 20 K, the Mössbauer spectra for 1/Dy are affected by magnetic relaxation effects. At 1.5 K, the spectrum of 1/Dy comprises well defined magnetic sextets indicating relaxation times slower than the characteristic time of the Mössbauer technique (10−7 s) in agreement with the dynamic magnetic measurements. 1/Gd exhibits broad unresolved magnetic sextets at 1.5 K indicating that the spin relaxation time is of the order of the Mössbauer characteristic time at this temperature. For 1/Tb, 1/Ho the Mössbauer spectra exhibit slight broadening even at the lowest available temperature consistent with magnetic relaxation times less than 10−7 s. [ABSTRACT FROM AUTHOR]