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The Ca2Pd2Ge-type stannides Sr2Pd2Sn and Eu2Pd2Sn were synthesized by reaction of the elements in sealed tantalum ampoules in a high-frequency furnace and characterized by powder X-ray diffraction. The structure of Sr2Pd2Sn (Fdd2, a = 1063.95(5), b = 1623.22(9), c = 594.63(14) pm, wR2 = 0.0472, 972 F 2 values and 26 variables) was refined from single-crystal X-ray diffractometer data. The striking structural motif features equidistant chains formed by the palladium atoms (304.7 pm Pd–Pd), which are interlinked by the tin atoms (266.9 and 268.7 pm Pd–Sn). Together, the palladium and tin atoms form a three-dimensional [Pd2Sn] δ– polyanionic network in which the strontium atoms reside in larger cavities. The divalent character of europium in Eu2Pd2Sn was manifested by 151Eu Mössbauer spectroscopy. The isomer shift is δ = −9.48(1) mm s−1 at room temperature. The results of 119Sn Mössbauer-spectroscopic experiments have confirmed the tin site determined by the single-crystal study, the isomer shifts being δ = 1.71(1) mm s−1 for Eu2Pd2Sn and δ = 1.73(1) mm s−1 for Sr2Pd2Sn. Sr2Pd2Sn is a Pauli paramagnet with a susceptibility of 2.2(1) × 10−5 emu mol−1 at room temperature. Eu2Pd2Sn shows Curie-Weiss paramagnetism with an experimental magnetic moment of 7.85(1) µB per Eu atom, confirming divalent europium. The europium magnetic moments order antiferromagnetically at T N = 14 K.

The silicide Eu2Ru3Si5 was synthesized from the elements in a sealed tantalum tube in a high-frequency furnace, while the gallide Eu2Ir3Ga5 was obtained by arc-melting. Both structures were refined from single-crystal X-ray diffractometer data: P4/mnc, a = 1072.69(8), c = 569.55(5) pm, wR = 0.0453, 617 F 2 values, 31 variables for Eu2Ru3Si5 and a = 1122.18(7), c = 583.17(4) pm, wR = 0.0546, 729 F 2 values, 31 variables for Eu2Ir3Ga4.95(1). The gallide shows small defects on one 8h site. The transition metal atoms in Eu2Ru3Si5 and Eu2Ir3Ga5 have octahedral p element coordination. These Ru@Si6 respectively Ir@Ga6 polyhedra are condensed to three-dimensional [Ru3Si5]6− respectively [Ir3Ga5]4− polyanionic networks. The ground states of Eu(III) in Eu2Ru3Si5 and Eu(II) in Eu2Ir3Ga5 were determined by 151Eu Mössbauer spectroscopy.

The silicides RE 3Pd20Si6 (RE = Sc, Y and Lu) were synthesized from the elements by arc-melting. The structures of Y3Pd20Si6 and Lu3Pd20Si6 were refined from single crystal X-ray diffractometer data: Mg3Ni20B6 type, F m 3 ‾ m $Fm\overline{3}m$ , a = 1216.04(8) pm, wR = 0.0328, 219 F 2 values, 14 variables for Y3Pd20Si6 and a = 1211.69(10) pm, wR = 0.0374, 217 F 2 values, 14 variables for Lu3Pd20Si6. The isotypy of Sc3Pd20Si6 was confirmed on the basis of a Guinier powder pattern (a = 1202.8(3) pm). The RE 3Pd20Si6 structures contain two crystallographically independent RE sites with relatively large coordination numbers, i.e. RE1@Pd16 and RE2@Pd12Si6. These polyhedra are arranged in a CaF2 related pattern with RE2@Pd12Si6 forming the fcc substructure and the RE1@Pd16 polyhedra filling the tetrahedral voids. The silicon atoms have slightly distorted square antiprismatic palladium coordination (4 × 239 pm Si–Pd1 and 4 × 245 pm Si–Pd2). Temperature dependent magnetic susceptibility measurements of the Lu3Pd20Si6 sample indicate Pauli paramagnetism.

The stannide BaRhSn2 was synthesized by induction melting of an arc-melted RhSn2 precursor compound with barium in a sealed tantalum ampoule. The structure of BaRhSn2 was refined from single-crystal X-ray diffractometer data: MgCuAl2 type, Cmcm, a = 437.56(4), b = 1242.35(10), c = 767.30(6) pm, wR2 = 0.0845, 469 F 2 values and 16 variables. The rhodium and tin atoms form a two-dimensional [RhSn2] δ− polyanionic network with short Rh–Sn (273–274 pm) and Sn–Sn (303–312 pm) distances. The large barium atoms lead to a substantial orthorhombic distortion of the (lonsdaleite-related) tin substructure, forcing a break of the Sn–Sn bond in b direction. This change in the tin substructure is reflected in the 119Sn Mössbauer spectrum. The tin atoms exhibit a higher s electron density which is expressed in an increased isomer shift of δ = 2.08(1) mm s−1 as compared to the previously reported stannide CaRhSn2 with a three-dimensional [RhSn2] δ− polyanionic network and δ = 1.96(4) mm s−1.

Several Lu26 T 17−x In x (T = Rh, Ir, Pt) phases with varying x values were obtained by induction-melting reactions of the elements in sealed tantalum ampoules. All samples were characterized through their X-ray powder diffraction patterns. These compounds crystallize with the tetragonal Sm26Co11Ga6-type structure, space group P4/mbm and Z = 2. The structure of Lu26Pt7.55In9.45 has been refined from single-crystal X-ray diffractometer data: a = 1165.32(5), c = 1547.46(6) pm, wR2 = 0.0895, 2173 F 2 values and 70 variables. The Lu26 T 17−x In x phases are the first indium representatives of the Sm26Co11Ga6 type. They belong to the n = 4 members of Parthé’s A 5n+6 B 3n+5 series, which show different stacking sequences of square prisms and antiprisms. Lu26Pt7.55In9.45 as a lutetium-rich intermetallic compound exhibits a broader range of shorter Lu–Lu distances (341–375 pm). Temperature dependent magnetic susceptibility measurements show Pauli paramagnetism for Lu26Ir8.5In8.5 and Lu26Rh7In10 with room temperature values of the magnetic susceptibility of χ = 1.53 × 10−3 emu mol−1 for Lu26Rh7In10 and χ = 6.54 × 10−4 emu mol−1 for Lu26Ir8.5In8.5.

The stannide YbRhSn2 has been synthesized. An arc-melted Rh25Sn48 precursor sample was reacted with ytterbium in a sealed tantalum ampoule in an induction furnace. The structure of YbRhSn2 was refined from single-crystal X-ray diffractometer data: MgCuAl2 type, Cmcm, a = 433.10(3), b = 1076.63(8), c = 739.36(5) pm, wR2 = 0.0676, 444 F 2 values and 16 variables. The rhodium and tin atoms form a three-dimensional [RhSn2] δ− polyanionic network with short Rh–Sn (271–273 pm) and Sn–Sn (301–324 pm) distances. The tin substructure is an orthorhombically distorted lonsdaleite network. YbRhSn2 shows paramagnetic behavior with a reduced magnetic moment of 2.2(1) µB per ytterbium atom, classifying it as an intermediate-valent compound.

CoIn2 (Z. Metallkd. 1970, 61, 342–343) forms by reaction of the elements at 1470 K followed by annealing at 770 K for five days. The room temperature structure is orthorhombic (CuMg2 type, Fddd, a = 529.95(10), b = 940.49(13), c = 1785.8(3) pm, wR2 = 0.0563, 444 F 2 values, 17 variables) and shows a phase transition at 195(1) K (DSC data). The low-temperature modification crystallizes in the translationengleiche monoclinic subgroup C2/c and exhibits a new structure type (a = 933.7(7), b = 526.91(10), c = 1000.8(2) pm, β = 117.81(5)°, wR2 = 0.0374, 843 F 2 values, 30 variables). The structural phase transition is a consequence of a Peierls type distortion. The equidistant cobalt chains in HT-CoIn2 (270.1 pm, 175.2° Co–Co–Co) show pairwise dislocation in LT-CoIn2 with shorter (252.4 pm) and longer (284.1 pm) Co–Co distances. Each cobalt atom has coordination number 10 in the form of slightly distorted square antiprisms of indium, capped by cobalt on the rectangular faces. Density-of-states calculations reveal metallic behavior for both modifications. Integrated crystal orbital overlap populations featuring the bonding characteristics indicate a slightly higher intensity area for LT-CoIn2 along with a shift to lower energy, manifesting the stabilization by pair formation through Peierls distortion.

Phase analytical studies in the Sc–Cu–In system led to samples of the solid solutions ScCu1–x–y In1+x and ScCu2–x In which were studied by X-ray powder diffraction. At room temperature the compounds ScCu1–x–y In1+x crystallize with the ZrNiAl type, space group P 6 ‾ $\overline{6}$ 2m. Exemplarily, the structure of ScCu0.76In1.17 was refined from single crystal X-ray diffractometer data, revealing strong anisotropic displacements for the scandium atoms and a mixed occupied Cu/In site. Superstructure formation is observed at low temperatures. The ScCu0.78In1.14 and ScCu0.76In1.16 structures were refined from diffraction data recorded at 90 K. Both compounds adopt the HfRhSn type, space group P 6 ‾ $\overline{6}$ 2c, a klassengleiche subgroup of index 2; doubling of the subcell c axis. The Cu/In filled trigonal Sc6 prisms are strongly distorted in the superstructure, resulting from pairwise dislocation of the Cu/In atoms from ideal positions within an equidistant chain to shorter (311.0 pm) and longer (392.8 pm) Cu/In–Cu/In distances. Single crystal data of the Heusler phases ScCu1.95In and ScCu1.94In show small degrees of copper vacancies.

A series of Pd(ii) and Pt(ii) complexes bearing tetradentate ligands as dianionic luminophores were synthesized and their room-temperature photoluminescence in PMMA films as well as in mechanochromic crystalline phases was correlated with molecular structure.

The equiatomic metal-rich phosphide NbCrP shows a structural phase transition around 125 K. The structures of the high- and low-temperature modifications were refined from single crystal X-ray diffractometer data of an un-twinned crystal: TiNiSi type, Pnma, a = 619.80(2), b = 353.74(4), c = 735.24(6) pm, wR = 0.0706, 288 F 2 values, 20 variables at 240 K and P121/c1, a = 630.59(3), b = 739.64(4), c = 933.09(5) pm, β = 132.491(6)°, wR = 0.0531, 1007 F 2 values, 57 variables at 90 K. The structural phase transition is of a classical Peierls type. The equidistant chromium chain in HT-NbCrP (353.7 pm Cr–Cr) splits pairwise into shorter (315.2 pm) and longer (373.2 pm) Cr–Cr distances. This goes along with a strengthening of Cr–P bonding. The superstructure formation is discussed on the basis of a group–subgroup scheme. Electronic structure calculations show a lifting of band degeneracy. Protection of the non-symmorphic symmetry of space group Pnma is crucial for the phase transition. The estimated charge modulation is consistent with the interpretation as Peierls transition.

The equiatomic indide ScPtIn (ZrNiAl type, space group P 6 ‾ $‾{6}$ 2m) shows an extended solid solution Sc3Pt3–xIn3. Several samples of the Sc3Pt3–xIn3 series were synthesized from the elements by arc-melting and subsequent annealing, or directly in a high frequency furnace. The lowest platinum content was observed for Sc3Pt2.072(3)In3. All samples were characterized by powder X-ray diffraction and their lattice parameters and several single crystals were studied on the basis of precise single crystal X-ray diffractometer data. The correct platinum occupancy parameters were refined from the diffraction data. Decreasing platinum content leads to decreasing a and c lattice parameters. Satellite reflections were observed for the Sc3Pt3–xIn3 crystals with x = 0.31–0.83. These satellite reflections could be described with a modulation vector ( 1 3 , 1 3 , γ ) $\left(\frac{1}{3},\frac{1}{3},\gamma \right)$ ( γ = 1 2 $\gamma =\frac{1}{2}$ c* for all crystals) and are compatible with trigonal symmetry. The interplay of platinum filled vs. empty In6 trigonal prisms is discussed for an approximant structure with space group P3m1.

The structures of the equiatomic stannides RERhSn with the smaller rare earth elements Y, Gd-Tm and Lu were reinvestigated on the basis of temperature-dependent single crystal X-ray diffraction data. GdRhSn crystallizes with the aristotype ZrNiAl at 293 and 90 K. For RE = Y, Tb, Ho and Er the HP-CeRuSn type (approximant with space group R3m) is already formed at room temperature, while DyRhSn adopts the HP-CeRuSn type below 280 K. TmRhSn and LuRhSn show incommensurate modulated variants with superspace groups P31m(1/3; 1/3; γ) 000 (No. 157.1.23.1) (γ = 3/8 for TmRhSn and γ = 2/5 for LuRhSn). The driving force for superstructure formation (modulation) is a strengthening of Rh–Sn bonding. The modulation is expressed in a 119Sn Mössbauer spectrum of DyRhSn at 78 K through line broadening.

In this work, a series of γ-substituted diphenylnaphthalonitriles were synthesized and characterized. They show efficient emission in solution and in the aggregated state and their environment responsiveness is based on having variable substituents at the para-position of the two phenyl moieties. The excited state properties were fully investigated in tetrahydrofuran (THF) solutions and in THF/H2O mixtures. The size of the aggregates in aqueous media were measured by dynamic light scattering (DLS). The steady-state and time-resolved photoluminescence spectroscopy studies revealed that all the molecules show intense fluorescence both in solution and in the aggregated state. In THF solutions, a blue emission was observed for the unsubstituted (H), methyl- (Me) and tert-butyl- (t-Bu) substituted γ-diphenylnaphthalonitriles, which can be attributed to a weak π-donor capability of these groups. On the other hand, the methoxy- (OMe), methylsulfanyl- (SMe) and dimethylamino- (NMe2) substituted compounds exhibit a progressive red-shift in emission compared to H, Me and t-Bu due to a growing π-electron donating capability. Interestingly, upon aggregation in water-containing media, H, Me and t-Bu show a slight red-shift of the emission and a blue-shift is observed for OMe, SMe and NMe2. The crystal structure of Me allowed a detailed discussion of the structure–property relationship. Clearly, N-containing substituents such as NMe2 possess more electron-donating ability than the S-based moieties such as SMe. Moreover, it was found that NMe2 showed higher luminescence quantum yields (ΦF) in comparison to SMe, indicating that N-substituted groups could enhance the fluorescence intensity. Therefore, the π-donor nature of the substituents on the phenyl ring constitutes the main parameter that influences the photophysical properties, such as excited state lifetimes and photoluminescence quantum yields. Hence, a series of highly luminescent materials from deep blue to red emission depending on substitution and environment is reported with potential applications in sensing, bioimaging and optoelectronics.

The scandium-rich intermetallic compounds Sc50T13In3(T = Ni, Ru, Pd) were synthesized from the elements in sealed tantalum crucibles in an induction furnace. The samples were studied through Guinier powder patterns and their structures were refined from single-crystal X-ray diffractometer data. The Sc50T13In3phases are site occupancy (coloring) variants of the aristotype Ag7+xMg26–x(Fm$$ \bar{3} $$3¯,cF264). Refinements of the occupancy parameters indicated one mixed occupied site for each crystal, leading to the refined compositions Sc50Ni13.16(1)In2.84(1), Sc49.59(1)Ru13In3.41(1), and Sc50Pd13.65(2)In2.35(2). The complex structures can be explained by a condensation of cubes (CN 8), sphenocorona (CN 10), and icosahedra (CN 12). The samples with nickel and palladium are Pauli paramagnets.Graphic abstract

The scandium-rich indide Sc50Pt13.47In2.53 was obtained by induction melting of the elements and subsequent annealing. The structure of Sc50Pt13.47In2.53 has been refined from single-crystal X-ray diffractometer data: Fm 3 ¯ $\overline{3}$ , a = 1774.61(3) pm, wR2 = 0.0443, 1047 F2 values and 35 variables. Sc50Pt13.47In2.53 is isopointal with the intermetallic phases Sc50Co12.5In3.5, Sc50Rh13.3In2.7, Sc50Ir13.6In2.4, Ag7+xMg26−x and Ga4.55Mg21.85Pd6.6 (Pearson code cF264 and Wyckoff sequence ih 2 fecba). Two of the eight crystallographic sites in the structure show mixed occupancies: M1 (≡Pt20.70In10.30) and M2 (≡Pt30.76In20.24). The structure contains four basic polyhedra: M2@Sc8 cubes, Pt1@Sc10 sphenocorona and slightly distorted M1@Sc12 and In3@Sc12 icosahedra. The polyhedra are condensed via common scandium corners and edges. The various Sc–Sc distances range from 302–334 pm and are indicative of substantial Sc–Sc bonding, stabilizing the Sc50Pt13.47In2.53 structure.

The quaternary gallium-rich intermetallic phases RE 2Pt3Ga4In with RE = Y and Gd-Tm were synthesized by arc-melting of the elements and subsequent annealing. Small single crystals were obtained by high-frequency annealing of the samples in sealed tantalum ampoules. The polycrystalline samples were characterized through their X-ray powder patterns. The RE 2Pt3Ga4In phases crystallize with a site ordering variant of the orthorhombic Y2Rh3Sn5 type, space group Cmc 21. The structures of Gd2Pt3Ga4In, Dy2Pt3Ga4.14In0.86, Er2Pt3Ga4.17In0.83 and Tm2Pt3Ga4.21In0.79 were refined from single-crystal X-ray diffraction data. The single crystals reveal small homogeneity ranges RE 2Pt3Ga4±xIn1±x. The striking geometrical structural building units are slightly distorted trigonal prisms around the three crystallographically independent platinum atoms: Pt1@RE 4Ga2, Pt2@RE 2Ga4 and Pt3@RE 2Ga2In2. Based on these prismatic building units, the RE 2Pt3Ga4In structures can be described as intergrowth variants of TiNiSi and NdRh2Sn4 related structural slabs. Temperature dependent magnetic susceptibility studies of Gd2Pt3Ga4In and Tb2Pt3Ga4In show Curie-Weiss behavior and the experimental magnetic moments confirm stable trivalent gadolinium respectively terbium. Gd2Pt3Ga4In and Tb2Pt3Ga4In order antiferromagnetically at T N = 15.8(1) and 26.0(1) K. Magnetization curves at 3 K show field-induced spin reorientations.

Systematically twinned olivenite (Cu2(AsO4)OH) single crystals from Cap Garonne, Mine du Pradet, France, were studied by X-ray diffraction: P 21/n, a = 822.69(6) pm, b = 861.88(9) pm, c = 594.06(9) pm, β = 90.000(6)°, wR = 0.0224, 1621 F 2 values, 79 variables and a domain ratio of 0.501(1)/0.499(1). The temperature dependence of the magnetic susceptibility was well reproduced with a square-spin cluster model and an antiferromagnetic spin-exchange parameter of J/k B = 157(3) K.

The indium-rich intermetallic compound CaPtIn4 is formed in a peritectic reaction of CaPtIn2 and indium metal at T = 670 K (14 days annealing). CaPtIn4 crystallizes with the YNiAl4-type structure, space group Cmcm, which was refined from single crystal X-ray diffractometer data: a = 446.3(5), b = 1659.50(18), c = 756.8(8) pm, wR2 = 0.0646, 640 F 2 values and 24 variables. Geometrically one can describe the CaPtIn4 structure as an intergrowth variant of CaPtIn2 (MgCuAl2 type) and indium slabs. The three-dimensional [PtIn4] polyanionic network shows short Pt–In distances of 269–280 pm and a broader range of In–In distances (304–378 pm) within substantially distorted In@In8 cubes.

Sr4In13Pt9 and Eu5In9Pt7 were synthesized by induction melting of the pure elements in glassy carbon crucibles. Both compounds were characterized through their X-ray powder patterns and the structures were refined from X-ray single crystal diffractometer data: Ho4Ir13Ge9 type, Pmmn, a = 439.17(5) pm, b = 1232.2(2) pm, c = 2135.3(3) pm, wR2 = 0.0550, 3598 F2 values, 88 variables for Sr4In13Pt9 and Sc5Pt9Si7 type, $$P{\bar{6}}$$ , a = 1116.7(2) pm, c = 435.86(7) pm, wR2 = 0.0379, 1358 F2 values, 45 variables for Eu5In9Pt7. The platinum and indium atoms form covalently bonded [In13Pt9] and [In9Pt7] polyanionic networks which exhibit larger tunnels for the strontium and europium cations. They bind to these networks through electrostatic interactions as is evident from shorter Sr–Pt (339–353 pm) and Eu–Pt (298–334 pm) contacts. Temperature-dependent magnetic susceptibility measurements of Eu5In9Pt7 show Curie–Weiss behavior with an experimental magnetic moment of 7.51(1) µB/Eu, indicating stable divalent europium. This is corroborated by 151Eu Mossbauer spectroscopy. Eu5In9Pt7 orders antiferromagnetically at 11.6(5) K and shows a metamagnetic transition in the 2.5 K isotherm at a critical field of 2 kOe.

Rod-shaped single crystals of Sr4Pt10In21 were prepared from the elements in glassy-carbon crucibles in a high-frequency furnace. The structure of Sr4Pt10In21 was refined from single-crystal X-ray diffractometer data: C2/m, Ho4Ni10Ga21 type, a = 2322.62(7), b = 450.27(2), c = 1958.09(7) pm, β = 133.191(3)°, wR = 0.0464, 3200 F 2 values and 107 variables. The three-dimensional [Pt10In21]δ− polyanionic network is stabilized through substantial Pt–In (269–313 pm Pt–In) and In–In (294–362 pm In–In) bonding. All platinum atoms have slightly distorted tri-capped trigonal prismatic coordination and the two crystallographically independent strontium atoms are located in penta-capped pentagonal prisms.

Natural lead dioxide samples (β modification) from Cap Garonne, Mine du Pradet, France and Mount Trevasco, Italy were studied by single crystal X-ray and electron diffraction, clearly manifesting the rutile-type structure. A needle from the Mount Trevasco sample was investigated on a single crystal diffractometer: P42/mnm, a = 495.81(10), c = 338.66(7) pm, wR = 0.0513, 117 F 2 values (all data) and nine variables (293 K data). An additional data set at T = 90 K gave no hint for structural distortions.

Single crystals of the high-temperature modification of RhSn4 were obtained from a tin flux (1:20 molar ratio; final annealing at 920 K; dissolution of the tin matrix in 2N HCl). The structure was refined from single-crystal X-ray diffractometer data: I41/acd, a=629.73(5), c=2288.36(18) pm, wR2=0.0382, 447 F 2 values and 14 variables. β-RhSn4 is isotypic with β-IrSn4. The rhodium atoms have slightly distorted square-antiprismatic tin coordination with Rh–Sn distances of 4×273.4 and 4×274.1 pm. The RhSn8 units are condensed via common edges to layers that are staggered with respect to each other and stacked in ABCD sequence. A 119Sn Mössbauer spectroscopic characterization of ß-RhSn4 and the stannides RhSn3 and α-RhSn4 shows the typical isomer shifts for transition metal stannides. Only for α-RhSn4 the three crystallographically independent tin sites could be resolved, a consequence of the different s-electron density. Treatment of α-RhSn4 under high-pressure (up to 10 GPa)/high-temperature (up to T=1370 K) conditions leads to decomposition into Rh1.5Sn, RhSn2 and β-Sn.

In this work, we describe the synthesis, structural and photophysical characterization of four novel Pd(ii) and Pt(ii) complexes bearing tetradentate luminophoric ligands with high photoluminescence quantum yields (ΦL) and long excited state lifetimes (τ) at room temperature, where the results were interpreted by means of DFT calculations. Incorporation of fluorine atoms into the tetradentate ligand favors aggregation and thereby, a shortened average distance between the metal centers, which provides accessibility to metal–metal-to-ligand charge-transfer (3MMLCT) excimers acting as red-shifted energy traps if compared with the monomeric entities. This supramolecular approach provides an elegant way to enable room-temperature phosphorescence from Pd(ii) complexes, which are otherwise quenched by a thermal population of dissociative states due to a lower ligand field splitting. Encapsulation of these complexes in 100 nm-sized aminated polystyrene nanoparticles enables concentration-controlled aggregation-enhanced dual emission. This phenomenon facilitates the tunability of the absorption and emission colors while providing a rigidified environment supporting an enhanced ΦL up to about 80% and extended τ exceeding 100 μs. Additionally, these nanoarrays constitute rare examples for self-referenced oxygen reporters, since the phosphorescence of the aggregates is insensitive to external influences, whereas the monomeric species drop in luminescence lifetime and intensity with increasing triplet molecular dioxygen concentrations (diffusion-controlled quenching)., Pt(ii) and Pd(ii) complexes with unprecedented photophysical properties were developed. Encapsulation in nanoparticles boosted their performance while rendering them as self-referenced oxygen sensors.

In this work, for the first time, the comparative use of P-, As-, and Sb-based ligands in phosphorescent coordination compounds is reported toward new coordination chemical concepts in the design and realization of tailored triplet emitters with nonconventional elements. By means of spectroscopic, X-ray diffractometric, and quantum-chemical methods, we reconstructed the nature of the chemical bonds as well as the influence of the increasingly heavy elements on the photoexcited state properties, which were correlated with the hybridization and polarizability of the pnictogen atoms (Pn). In particular, we elucidated the structural and photophysical properties of a series of homologous Pt(II) complexes with monodentate ancillary ligands based on group 15 elements, namely P, As, and Sb. Six coordination compounds bearing tridentate dianionic 2,6-bis(1H-1,2,4-triazol-5-yl)pyridine luminophoric pincer ligands bearing either CF3 or tBu moieties on the triazole rings along with triphenylpnictogens (PnPh3) as monodentate ancillary ligands ([CF3/Pn] or [tBu/Pn], respectively) have been investigated. The electron donating or withdrawing effect of the peripheral substituent (tBu vs. CF3, respectively) and its influence on the bonding, crystal packing as well as the excited state energies and lifetimes was assessed in fluid solutions, frozen glassy matrices, amorphous solids, and crystalline phases. A progressively red-shifted phosphorescence was observed with increasing atomic number along with a growing compensation of hybridization defects upon coordination of the Pn atom to the Pt(II) center. The change of molecular geometry of the PnPh3 unit upon complexation was extrapolated to predict the structural and excited state characteristics of the Bi-based analogues, which according to DFT calculations should be stable species and are the subject of ongoing synthetic efforts. In general, we envisage the use of these ligands for the relativistic enhancement of radiative deactivation rate processes, especially if Bi-based s-orbitals participate on the bond with the metal center, paving the road toward novel coordination compounds using abundant elements with high spin-orbit coupling for sustainable electroluminescent devices.

Natural orthorhombic sulfur (α-S8), grown on galena crystals from Cap Garonne, Mine du Pradet, France, were studied by single crystal X-ray diffraction at 150 K: Fddd, a=1036.75(5), b=1273.54(7), c=2437.85(13) pm, wR=0.0380, 1433 F 2 values (all data) and 37 variables. Refinements of the occupancy parameters along with EDX data indicate pure sulfur.

Two dinuclear metal complexes bearing the purine derivative 7-methyl-6-furylpurine (1b) as a ligand are reported. In [Ag2(1b)2(DMSO)2](ClO4)2·DMSO and [Cu2(1b)2(NO3)2], two bridging purine derivatives coordinate the two metal ions via their N3 and N9 positions. In the silver(I) complex, the coordination environment of each metal ion is completed by a DMSO ligand, whereas an additional nitrato ligand coordinates to each copper(I) ion. The intramolecular Ag···Ag distance of 3.1069(5) Å is in agreement with the presence of a weak argentophilic interaction, whereas the Cu···Cu distance of 2.9382(4) Å is too long to be indicative of a cuprophilic interaction. The compounds represent the first examples of dinuclear complexes comprising two N3,N9-bridging purine derivatives without any additional bridging ligand.

Dimeric germole dianion bridged TiIII and ZrIV complexes have been synthesized. In these complexes, the germole dianion adopts a formal η1 ,η5 coordination to the two metal centers. The bonding situation in these bridged dimers is dominated by a covalent Ge-Ge interaction that results, for example, in a strong antiferromagnetic coupling of the d1 Ti centers.

The germanides Sr3Pd4Ge4 and BaPdGe were obtained from high-temperature reactions in sealed niobium ampoules and their structures have been determined from single-crystal X-ray diffraction data: a=444.2(1), b=438.1(1), c=2472.2(7) pm, space group Immm, U3Ni4Si4 type, wR2=0.0471, 576 unique reflections, 25 parameters for Sr3Pd4Ge4 and a=677.09(8), space group P213, LaIrSi type, wR2=0.0322, 409 unique reflections, nine parameters for BaPdGe. Both germanides have pronounced three-dimensional [Pd4Ge4] δ− and [PdGe] δ− polyanionic networks with Pd–Ge bonding interactions. This is confirmed by the density functional theory (DFT)-based electronic structure investigations, the trends of charge transfer and crystal orbital overlap population (COOP) analyses.

The stannide Sm2Rh3Sn5 was obtained by arc-melting of the elements and subsequent annealing at 1070 K in a silica tube. Sm2Rh3Sn5 crystallizes with the orthorhombic Y2Rh3Sn5 type structure, space group Cmc21, Z=4: a=444.46(8), b=2636.2(4), c=718.3(1) pm, wR=0.0711, 1761 F 2 values and 61 variables. The three crystallographically independent rhodium atoms show tricapped trigonal prismatic coordination by samarium and tin atoms. Sm2Rh3Sn5 can be considered as a simple 1:1 intergrowth structure of TiNiSi- and NdRh2Sn4-related slabs of compositions SmRhSn and SmRh2Sn4 . Temperature dependent magnetic susceptibility data revealed van Vleck type behavior caused by the proximity of the exited 6H7/2 state to the 6H5/2 ground state of Sm3+, and an antiferromagnetic ordering occurs at T N=3.5(5) K.

A paramagnetic WIII alkyne complex bearing free terminal diphenylphosphino groups at the side-on coordinated alkyne was synthesized using a stepwise template strategy. This moderately stable metal supported open shell diphosphine shows an unprecedented spontaneous splitting of nitric oxide providing a WII-η2-C2{P(NH2)Ph2}{P(O)Ph2}+ complex featuring an amino phosphonium and a phosphine oxide substituent.

Three new complexes bearing the tridentate hydrazone-based ligand 2-(2-(1-(pyridin-2-yl)ethylidene)hydrazinyl)pyridine (L) were synthesized and structurally characterized. Biological tests indicate that the Zn(II) complex [ZnCl2(L)] is of low cytotoxicity against the hepatocellular carcinoma cell line HepG2. In contrast, the Cu(II) and Mn(II) complexes [CuCl2(L)] and [MnCl2(L)] are highly cytotoxic with EC50 values of 1.25 ± 0.01 μM and 20 ± 1 μM, respectively. A quantitative proteome analysis reveals that treatment of the cells with the Cu(II) complex leads to a significantly altered abundance of 102 apoptosis-related proteins, whereas 38 proteins were up- or down-regulated by the Mn(II) complex. A closer inspection of those proteins regulated only by the Cu(II) complex suggests that the superior cytotoxic activity of this complex is likely to be related to an initiation of the caspase-independent cell death (CICD). In addition, an increased generation of reactive oxygen species (ROS) and a strong up-regulation of proteins responsive to oxidative stress suggest that alterations of the cellular redox metabolism likely contribute to the cytotoxicity of the Cu(II) complex.

The YCrB4 type borides YTB4 (T = Mo, W, Re) were synthesized from the elements by arc-melting and subsequent annealing. The structures were refined from single crystal X-ray diffractometer data: Pbam, a = 602.84(8), b = 1164.5(1), c = 361.20(4) pm, wR2 = 0.0404, 624 F2 values, 26 variables for YMoB4, a = 603.00(7), b = 1165.1(1), c = 360.63(6) pm, wR2 = 0.0487, 474 F2 values, 26 variables for YWB4, and a = 596.67(6), b = 1154.4(1), c = 360.21(4) pm, wR2 = 0.0465, 544 F2 values, 26 variables for YReB4. The boron atoms build up planar networks which are a tessellation of slightly distorted pentagons and heptagons. Adjacent networks coordinate the transition metal and yttrium atoms in the form of pentagonal and heptagonal prisms, respectively. The four crystallographically distinct boron sites are differentiated by high-resolution 11B solid state isotropic magnetic shifts and nuclear electric quadrupolar coupling constants. Partial site assignments are possible based on comparisons with electric field gradient calculations using the WIEN2k code. 89Y MAS NMR spectroscopic studies suggest substantially weaker Knight shift contributions to the resonance frequencies when compared to other intermetallic yttrium compounds, including other ternary yttrium boride compounds measured previously.

The synthesis and structure of [Ag(9-methyl-6-furylpurine)(NO3)] n are reported. The title compound represents a rare example of a purine derivative metalated at all three endocyclic nitrogen atoms. It forms a two-dimensional coordination polymer comprising 14-membered trinuclear metallacycles. Density functional theory calculations helped to understand the metal-binding behavior of the 6-furylpurine moiety by showing the silver(I)-binding affinities of all three nitrogen donor atoms to be essentially identical under aqueous conditions.

Hydroalumination of H10C5N–N=C(Ad) with HAliBu2 yielded the hydrazide H10C5N–N(AliBu2)Ad (4; Ad = adamantyl, NC5H10 = piperidinyl). Compound 4 is monomeric and contains a highly strained AlN2 heterocycle formed by a donor–acceptor interaction between the Al atom and the β-N atom of the hydrazine. Two equivalents of the hydride afforded an adduct with an HAliBu2 molecule coordinated to 4 by an Al–N and a 3c–2e Al–H–Al bond (5). tBuN=C=O did not insert into the relatively weak AlN donor–acceptor bond of 4; instead, insertion into the shorter Al–N(amide) bond yielded five-membered AlN3C heterocycle 6 with an exocyclic C=O group. PhN=C=O showed a similar reaction, but the product 7 was dimeric in the solid state with two Al–O bonds. Reaction in a 1:2 ratio afforded a unique linear dimer of phenyl isocyanate, which is stabilised by the aluminium hydrazide (8). Isothiocyanates gave thiosemicarbazides 9–11, which have Al atoms coordinated in a chelating manner by formation of AlSCN heterocycles and show fascinating differences in their bonding situation.

The Au(III)-mediated oxidative cyclization of a series of 2-hydrazinylquinolines is reported. This intramolecular reaction represents a reliable way towards obtaining various 3H-1,2,4-triazolo[4,3-a]quinolin-10-ium cations. The molecular structures of three of the starting compounds (2-(1-methyl-2-(pyridin-2-ylmethylene)hydrazinyl)quinoline, 2-(1-methyl-2-(thiophen-2-ylmethylene)hydrazinyl)quinoline, 2-((2-methyl-2-(quinolin-2-yl)hydrazono)methyl)aniline) as well as of one cyclized system (3-methyl-1-(pyridin-2-yl)-3H-1,2,4-triazolo[4,3-a]quinolin-10-ium dichloridoaurate(I)) were determined by means of single-crystal X-ray diffraction.

6-(3,5-Dimethylpyrazol-1-yl)purine has recently been introduced as an artificial nucleobase for the specific recognition of canonical nucleobases via the formation of a metal-mediated base pair. We report here the synthesis and structural characterization by single crystal X-ray diffraction analysis of a series of metal complexes of the corresponding alkylated model nucleobases 9-methyl-6-(3,5-dimethylpyrazol-1-yl)purine 2 and 9-methyl-6-pyrazol-1-yl-purine 7. The sterically more demanding ligand 2 forms the Cu(2+) complexes [Cu(2)(NO3)2] and [Cu(2)Cl2] with a 1:1 stoichiometry of ligand and metal ion. In contrast, ligand 7 forms complexes [Cu(7)2(NO3)](NO3) and [Ag(7)2](ClO4) with a 2:1 stoichiometry. The molecular structures of [Cu(2)(NO3)2] and [Cu(2)Cl2] confirm the previously suggested coordination pattern, i.e. Cu(2+) is coordinated via the pyrazole nitrogen atom and the purine N7 position. The fact that different relative orientations of the two ligands in [Cu(7)2(NO3)](NO3) and [Ag(7)2](ClO4) are observed allows the prediction that the corresponding metal-mediated homo base pairs should be stable both in regular antiparallel-stranded and in the rare parallel-stranded double helices.

Dimeric germole dianion bridged Ti

A CuII hydrazone complex has been synthesized that can be reduced in situ in boiling methanol to give the corresponding CuI complex. The latter complex readily activates dioxygen under ambient conditions, as was unambiguously shown by isotopic labeling studies. As a consequence of the dioxygen activation, the thienyl moiety appended to the hydrazone ligand is easily oxidized in β position (C–H C–O), finally leading to a change in the coordination environment of the central metal ion. All relevant complexes have been structurally characterized by single-crystal X-ray diffraction analyses. The hydrazone ligand applied in this study does not mimic a biologically relevant coordination motif in copper-containing oxygenases. Nonetheless, the reactivity of the CuI complex resembles that found in many oxygenases, indicating that hydrazone ligands may be well-suited for the generation of novel bioinspired oxidation catalysts.