Highly luminescent organic-inorganic hybrid materials have been prepared by combining task-specific polymerized ionic liquids (PILs) based on the 1-alkyl-3-vinylimidazolium cation ([CnVim]+ (with n = 2-6)) with suitable halides of trivalent lanthanides such as europium and terbium. The resulting materials have been characterized by 1H nuclear magnetic resonance, Fourier transform infrared, UV-Vis and photoluminescence spectroscopy. They show bright and intense luminescence over a wide range of excitation wavelengths, which particularly for the Eu3+ containing compounds, benefits from efficient energy transfer from the organic aromatic moieties in the PIL to the emitting level of the lanthanide(iii) ion. In the case of the Tb3+ ion, the emission benefits from excitation into the Tb3+ d levels. The emission colour can be tuned from green to red for Tb and Eu respectively. This includes bright white emission for Eu that can be achieved by altering the excitation wavelength. The easy processability of these novel PILs renders them interesting for a wide range of optical applications.

A set of IL-forming ion combinations has been studied to gain a deeper understanding of how, aside from obvious electrostatic interactions and ion size effects, secondary bonding such as hydrogen as well as halogen bonding and van der Waals interactions along with conformational and structural flexibility influence the crystallization behavior of potentially IL forming salts. The scrutinized ions have been specifically chosen to allow for unraveling preferential interactions of functional groups that may favor or disfavor crystallization with respect to secondary bonding interactions, i.e., primary and quaternary ammonium cations of variable alkyl chain lengths, which were also endowed with hydroxy groups, combined with formate and bis(trifluoromethanesulfonyl)amide anions. The background is to provide a deeper fundamental understanding of how to intentionally pair cations and anions that will not support the formation of a crystalline solid but rather IL formation, an approach described as “anti-crystal engineering”. This concept is based on the idea to avoid combining ions that are strong supramolecular synthons for crystallization. To this avail, the crystallization behavior of salts constituted of combinations of selected ions bearing different structural, supramolecular crystallization motifs has been studied in detail by low-temperature differential scanning calorimetry (DSC). Single crystal X-ray structure analysis has been used to elucidate ion packing and preferential interactions whenever crystalline solid formation is observed. The study reveals that the lowest melting points are supported by cation-anion combinations that have the least hydrogen bonding. However, if there are multiple possibilities of H-bonding for an ion with its counteranion, this bonding frustration leads as well to low melting points-albeit they are still higher compared to ion combinations with no H-bonding capacity. Through a careful balance of primary and secondary, directional and nondirectional interactions, it was possible to rationally identify a record class of ionic liquids, which combine exceptionally high decomposition points (440-450 °C) with an enormously high liquid range around of more than 500 °C and no tendency for solidification down to well below ambient temperature (−90 °C). These ILs are formed by bis(trifluoromethane)sulfonylamides with quaternary ammonium ions that bear an −OH group in the side chain.

Commonly accepted design concepts for ionic liquids (ILs) state that the constituting ions must be large and carry low, well-dispersed charges. A series of ILs based of pentadeca charged ILs with pentanuclear linear {Ln₅} units ([Ln₅(C₂H₅-C₃H₃N₂-CH₂COO)₁₆(H₂O)₈](Tf₂N)₁₅ (C₃H₃N₂ = imidazolium moiety, Tf₂N = bis(trifluoromethanesulfonyl)amide) with Ln = Er, Ho, Tm) demonstrates that these criteria are not absolute. Highly charged ions can also support IL formation, provided they are sufficiently large. Expanding the series of these unconventional, record pentadeca charged with new lanthanide representatives, led to the discovery of additional unprecedented properties for ILs: The Gd compound exhibits a strong magnetocaloric effect (MCE) in the liquid state with a maximum magnetic entropy change of −ΔS_M = −11 J⋅kg⁻¹⋅K⁻¹ at 2 K for Δμ₀H = 7 T. Albeit the Dy representative shows slow magnetic relaxation, the relaxation times are not favorable for practical application as a molecular magnet. Lastly, for both the Gd and the Y compound, phosphorescence in the seconds time scale is observed, which is, to the best of our knowledge, the longest ever reported for an IL.

Two new quaternary selenides of the alpha-TlSe structure type have been synthesized and characterized. Single crystal X-ray diffraction analysis has revealed that Tl2Ga2SnSe6 crystallizes with space group I4/mmc, a =8.095(1), c=6.402(1) angstrom, with a refined composition of Tl1-xGa1-ySny Se-2 (x= y=0.345(5)), Z=4, R1=0.028; wR2= 0.066. The crystal structure of the isostructural compound Tl2Ga2GeSe6 has been determined by means of powder X-ray diffraction: space group I4/mmc, Z= 4, a= 8.0770(4 ), c= 6.2572(5) angstrom, refined composition Tl1-xGa1-ySny Se-2, x=0343(5), y=0.35(2), (R-B(I) = 0.084; R-p = 0.041; R-PW= 0.058). According to their optical absorption spectra all compounds are semiconductors with relatively narrow direct band gaps of 2.15(3) and 2.05(5) eV for the Ge and Sn phase, respectively.

Ionic liquids present a versatile, highly tunable class of soft functional materials. Aside from being low melting salts, they can be endowed with additional functionalities. In N-alkylimidazolium halides, which are a prominent class of ionic liquids (ILs), the imidazolium cation was linked via an ether-bridge to an azobenzene unit in order to obtain photoresponsive materials through photoinduced trans-cis isomerization. The azobenzene unit, in turn, was modified with electron-donating or -withdrawing groups such as methyl-, tert-butyl-, methoxy-, N,N-dimethylamino, and nitro groups to study their influence on the photoisomerization and phase behavior. Endowing the imidazolium additionally with a long alkyl chain allows the materials to potentially form liquid crystalline (LC) mesophases before melting into the isotropic liquid. All studied compounds qualify as ionic liquids, and all, except for the nitro-compound, show the formation of smectic mesophases melting to the isotropic liquid. The compounds with the bulkiest aliphatic substituent, the tert-butyl, shows the lowest melting point, the largest mesophase window, and an efficient photochemical trans-cis conversion (>90%). In summary, by tuning sterically and electronically the cationic part of ILs, a photoswitchable room temperature liquid crystal could be developed and design guidelines for photoresponsive ionic liquids could be obtained.

Materials showing thermoelectric properties known as thermoelectrics can reversibly convert a temperature gradient into electricity. Since the vast majority of energy we use comes from thermal processes or creates thermal energy as waste energy, the search for materials able to efficiently convert thermal energy is of extreme importance. The discovery of a new, highly efficient thermoelectric material is complicated due to the special requirements imposed on the combination of electrical and thermal transport properties. Metal chalcogenides (MCs) have attracted significant attention as high performance thermoelectric materials. Their subgroup, active-transition-metal chalcogenides, shows structural and compositional diversity, including a wide occurrence of low-dimensional structural motifs, which opens up a fruitful area for explorations. This area has been preliminarily explored from both structural and functional viewpoints revealing very promising directions and unique compounds. Nevertheless, systematic investigations on transport properties are still missing. Available data suggests the presence of low bandgap semiconductors satisfying at least one of the conditions for a good thermoelectric, whereas the potential for structural and electronic variation in the form of active metal doping and substitution leaves a decent chance to uncover a candidate with acceptably low thermal conductivity and subsequently high thermoelectric performance.

Direct quaternization of 1-methyl-1,2,4-triazole with n-alkyl methanesulfonates (alkyl = butyl, octyl, dodecyl) showed to be an atom-economic, convenient, mild, solvent- and halide-free way to obtain 1,2,4-triazolium methanesulfonate ionic liquids in high purity and yield. Subsequent metathesis with lithium bis(trifluoromethanesulfonyl)amide (LiTf2N) allows for a much desired, easy access to halide-free, bis(trifluoromethanesulfonyl)amide ionic liquids. Differential scanning calorimetry confirms that all investigated compounds qualify as ionic liquids (ILs). Moreover, it reveals for 1-methyl-4-n-dodecyl-1,2,4-triazolium methanesulfonate a rather complex thermal behavior involving formation of mesophases. Indeed, polarizing optical microscopy shows oily streaky textures that are characteristic for smectic liquid crystalline phases. Single-crystal X-ray diffraction structure analysis confirms formation of a layered structure. All compounds are photoluminescent. The color of fluorescence at room temperature can be tuned from blue to orange through the length of the alkyl side chain of the cation, the aromatic interactions between the cations, and the anion nature. In addition, at low temperatures (77 K) a close to white phosphorescence with average lifetimes in the millisecond time range can be observed for 1-methyl-4-n-butyl-triazolium methanesulfonate and all of the studied bis(trifluoromethanesulfonyl)amide ILs. All ILs show an appreciable liquidus range and thermal (up to 260-350 degrees C) and electrochemical stability. The presented set of ILs overcomes the sometimes problematic acidity and low stability of imidazolium ILs in basic environment and can be obtained easily in high purity without halide contamination. Overcoming two shortcomings of classical imidazolium ILs, they may be good alternatives for a number of applications and even enabling new ones.

An ionothermal synthesis study of transition metal phosphates using the ionic liquid 1-butyl-4-methylpyridinium hexafluorophosphate [C(4)mpy] [PF6] yielded four new, different open framework manganese compounds, that is, K2Mn3 (HPO4)(2)(PO3F)F-2 (1), (NH4)(2)Mn-3 (HPO4)(2) (PO3F)-F-2 (2), KMn3 (H2PO4)(HPO4)(2)F-2 (3), and (NH4)Mn-3(H2PO4)(PO3F)(2)F-2 (4). The obtained products not only feature new framework topologies unprecedented in the family of phosphates but also interesting properties as the transition metal gives rise to both luminescent (rendering them potential nonrare earth containing red emitting phosphors) and unconventional magnetic properties governed by geometric frustrations. Aside from the structural analysis (powder and single-crystal X-ray diffraction, infrared spectroscopy), a variety of characterization methods (photoluminescence spectroscopy and magnetic measurements) were applied to study the material's properties. Single crystal X-ray studies reveal that 1 (P2(1)/c with a = 5.501(1), b = 14.203(3), c = 16.905(4) angstrom, beta = 108.65(3)degrees, V = 1251.4 angstrom(3), and Z = 4) and 2 (P2(1)/c with a = 5.587(1), b = 14.507(3), c = 17.364(3) angstrom, beta = 108.75(3)degrees, V = 1332.6(5) angstrom(3), and Z = 4) feature S-shaped 18-ring channels along [100], which are formed by trimer-Mn3O9F2 chains parallel to [100] and interconnecting PO3 (OH) and PO3F tetrahedra. The structure of compounds 3 (C2/c with a = 20.307(4), b = 7.635(1), c = 7.834(2) angstrom, beta = 103.26(3)degrees, V = 1182.2(4) angstrom(3), and Z = 4) and 4 (C2/c with a = 20.402(4), b = 7.673(1), c = 7.845(2) angstrom, beta = 103.56(3)degrees, V = 1193.8(4) angstrom(3), and Z = 4) are characterized by layers, which are built of Mn3O8F4 octahedra trimers, with Kagome topology parallel to the be plane featuring 3,6-ring channels. The layers are stacked according to a sequence of AA(i) along the a axis. Taking into account the [P(2)O-3(OH)/P(2)O3F] tetrahedra, the Kagome layers are replenished to a Mn3O2 (HPO4)/Mn3O2 (PO3F) composition, which are interlinked by [P(1)O-2(OH)(2)] forming 10-ring channels parallel to [001]. Charge compensation of the macroanions is achieved by K+ (1 and 3) and (NH4)(+) (2 and 4) cations. At room temperature, compounds 1-4 demonstrate a reddish orange emission ascribed to the spin-forbidden T-4(1g)((4)G) -> (6)A(1g) (S-6) transition of the Mn2+ ions. Upon lowering the temperature to 77 K, the emission of each compound is red-shifted and becomes pure red. Compounds 1 and 2 contain spin trimers with a presumable doubled ground state. The intertrimer magnetic coupling is relatively weak, and small ferrimagnetic domains are possible in 1. The magnetic behavior of 3 and 4 can be considered as antiferromagnetic. This can be understood as their staircase Kagome lattices are distorted, meaning that the intrinsic geometrical frustration is lifted.

A set of different open framework iron phosphates have been synthesized ionothermally using a task-specific ionic liquid, 1-butyl-4-methylpyridinium hexafluorophosphate, that acts in the synthesis as the reaction medium and mineralizer: (NH4)(2)Fe-2(HPO4)(PO4)Cl2F (1) and K2Fe2(HPO4(PO4)Cl2F (2) exhibit similar composition and closely related structural features. Both structures consist of {Fe-2(HPO4)(PO4)-Cl2F}(2)- macroanions and charge balancing ammonium or potassium cations. Their open framework structure contains layers and chains of corner-linked {Fe(1)O2Cl4} and {Fe(2)F2O4} octahedra, respectively, interconnected by PO4 tetrahedra forming 10-ring channels. KFe(PO3F)F-2 (3) is built up by {Fe[(PO3F)(4/3)F-2/2]}{Fe(PO3F)(2/3) F2/2F2} layers separated by K+ cations. Chains of alternating {FeF2O4} and {FeO2F4} octahedra, which are linear for 1 but undulated for 2, are linked to each other via corner-sharing {PO3F} tetrahedra with the fluorine pointing into the interlayer space. The compounds were characterized by means of single crystal and powder X-ray diffraction, infrared spectroscopy, and magnetic measurements. 1 reveals a strong ground state spin anisotropy with a spin 5/2 state and a magnetic moment of 5.3 mu(B) /Fe3+. Specific heat and magnetic data unveil three magnetic transitions at 95, 50, and 3.6 K. Compound 2 has a very similar crystal structure as compared to 1 but exhibits a different magnetic behavior: a slightly lower magnetic moment of 4.7 mu(B)/Fe3+ and a magnetic transition to a canted antiferromagnetic state below 90 K. Compound 3 exhibits typical paramagnetic behavior close to room-temperature (5.71 mu(B)/Fe3+). There are no clear indications for a phase transition down to 2 K despite strong antiferromagnetic spin-spin interactions; only a magnetic anomaly appears at 50 K in the zero-field cooled data.

Two isostructural series of lanthanide metal-organic frameworks denoted as SUMOF-7II (Ln) and SUMOF-7IIB (Ln) (Ln = La, Ce, Pr, Nd, Sm, Eu, and Gd) were synthesized using4,4',4 ''-(pyridine-2,4,6-triyl)tris(benzoic acid) (H(3)L2) and a mixture of H(3)L2 and 4,4',4 ''-(benzene-1,3,5-triyl)tris(benzoic acid) (H3BTB) as linkers, respectively. Both series were characterized using powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermal analysis (TGA), and photoluminescence spectroscopy. Photoluminescence measurements show that Eu-MOFs demonstrate a red emission while Pr- and Nd-MOFs display an emission in the near-infrared (NIR) range. On the other hand, La-, Ce-, Sm- and Gd-MOFs exhibit only a ligand-centered emission. The average luminescence lifetimes in the SUMOF-7IIB series are 1.3-1.4-fold longer than the corresponding ones in the SUMOF-7II series. SUMOF-7IIs show a good photo- and thermal stability. Altogether, the properties of SUMOF-7II and SUMOF-7IIB render them promising materials for applications including sensing, biosensing, and telecommunications.