Volume 233, Issue 7

Acetylacetone (2,4-pentanedione) derivatives with N donor substituents represent ditopic ligands with coordination sites of distinctly different Pearson hardness. Deprotonation of the acetylacetone (Hacac) moiety leads to O,O ′ chelating monoanionic (acac) ligands suitable for coordination to hard cations. The softer N donor site(s) preferably act as nucleophiles towards softer partners. When the organic molecules are employed as linkers and coordinate via either site, they are often selective and allow to synthesize well-ordered heterometallic solids. This review addresses the derivatives of 17 pentanediones with nitrile, pyridyl and pyrazolyl moieties as N donor substituents, with an emphasis on structurally characterized compounds. Depending on the N donor substituents and the cations, O,O ′ or N coordination will dominate. The nitrile-substituted compounds essentially behave as acetylacetones; they may easily O,O ′ coordinate to a wide range of cations whereas N coordination is limited to Ag I , Cu I or, in the case of less soft cations, to longer and presumably weaker contacts, e.g. to the more distant sites in Jahn–Teller distorted Cu II . In contrast, pyridyl-substituted pentanediones act as N donor ligands, regardless whether their (H)acac site is chelating a cation or not. The still scarcely explored pyrazolyl derivative shows the most complex coordination pattern: it may be deprotonated both at the acetylacetone and the pyrazol site, the latter affording N,N ′ bridging ligands. In addition to N donor nucleophilicity, the distance between the alternative coordination sites and their mutual orientation are relevant for crystal engineering applications.

Single crystals of Ca 9 Y(VO 4 ) 7 ( 1 ), Ca 9 Y(VO 4 ) 7 :Li + ( 2 ) and Ca 9 Y(VO 4 ) 7 :Mg 2+ ( 3 ) were grown by the Czochralski method. Their chemical composition was analyzed by ICP spectroscopy and their crystal structure was examined by single crystal X-ray analysis. The crystals are characterized by trigonal symmetry, space group R 3 c . Hexagonal unit-cell parameters are as follows: a =10.8552(1) Å, c =38.0373(2) Å, V =3881.65(1) Å 3 for 1 ; a =10.8570(1) Å, c =38.0161(3) Å, V =3880.77(4) Å 3 for 2 ; a =10.8465(1) Å, c =38.0366(2) Å, V =3875.36(3) Å 3 for 3 . All crystals are characterized by β -Ca 3 (PO 4 ) 2 -type structure with statistical distribution of Ca 2+ and Y 3+ over M 1, M 2 and M 5 sites in different ratios and with completely empty M 4-cationsite. The impurity of Mg 2+ cations in structure 2 has been detected in octahedral M 5 site. Ferroelectric phase transitions are evidenced by DSC and SHG. At about 1220 and 1300 K, they demonstrate phase transitions. Upon heating the symmetry of the crystal structure changes according to the scheme R 3 c → R 3̅ c → R 3̅ m and is restored during consequent cooling. The first of them is of ferroelectric and the second of non-ferroelectric nature. Even a small amount of impurities in Ca 9 Y(VO 4 ) 7 structure is accompanied by a noticeable decrease in the temperature of the ferroelectric-paraelectric phase transition.

The crystal structure of a Nb-rich zirconolite-3 T from the Laach Lake volcano, Eifel, Germany, was studied by single-crystal XRD ( R =0.0295). The mineral is trigonal, P 3 1 21; unit-cell dimensions are: a= 7.3095(2), c =16.9604(5) Å, V =784.78(4) Å 3 . The empirical formula based on 14 O atoms ( Z =3) is Ca 1.28 Ce 0.31 La 0.14 Nd 0.12 Pr 0.06 Th 0.16 Zr 1.94 Hf 0.04 Ti 1.74 Nb 1.22 Fe 0.72 Mn 0.28 O 14 . The crystal-chemical formula based upon the structural model is: VIII (Ca 0.70 Ce 0.30 ) VIII (Ca 0.58 Ce 0.32 Th 0.10 ) VII (Zr 0.88 Th 0.04 Hf 0.02 □ 0.06 ) 2 VII (□ 0.94 Zr 0.06 ) 2 VI (Ti 0.72 Nb 0.26 Zr 0.02 ) VI (Ti 0.50 Nb 0.47 Zr 0.03 ) 2 IV (Fe 0.355 Mn 0.145 ) 2 O 14 ( Z =3).

Mn 2+ -bearing eleonorite from the Hagendorf South pegmatite situated south of Waidhaus, Upper Palatinate, Bavaria, Germany was study based on single crystal X-ray analysis, Mn and Fe K -edge XANES spectroscopy, as well as IR spectroscopy. According to spectroscopic data, all Mn is bivalent, and all Fe is trivalent. The empirical formula of the mineral is (Mn 2+ 0.58 Zn 0.13 Mg 0.04 Fe 3+ 5.24 ) Σ5.98 (PO 4 ) 4 (H 2 O,OH,O) 11 . The monoclinic unit-cell parameters are: a =20.832(3) Å, b =5.1569(3) Å, c =19.200(2) Å, β=93.01(1)°; space group C 2/ c . The structure was refined to R 1 =5.20% in anisotropic approximation using 1994 reflections with I >3σ( I ). Despite in most beraunite-group minerals M 1-site demonstrates selective accumulation of bivalent cations, in Mn-bearing eleonorite Mn 2+ -cations are disordered between octahedral sites without statistical predominance anywhere; all octahedral M (1–4)-sites are predominantly occupied by Fe 3+ . M 1-site is half-occupied by Fe 3+ and contains subordinate Mn 2+ and minor Zn 2+ and Mg 2+ . Based on the new data we suppose that Mn-bearing eleonorite was formed as a secondary phase as a result of oxidation of a primary Mn-bearing beraunite-group mineral in with Mn 2+ was initially distributed between different M sites.

Na 3 GaF 6 and Na 3 GaF 6 :Mn 4+ samples were obtained from NaNO 3 and Ga(NO 3 ) 3 ·9H 2 O in hydrofluoric acid using K 2 MnF 6 or NaMnO 4 as manganese sources. The structure of Na 3 GaF 6 was studied by single crystal X-ray diffraction at 90, 293, 440 and 500 K, confirming the monoclinic cryolite type structure, space group P 2 1 / c . The gallium atoms show slightly distorted octahedral coordination by fluorine atoms, similar to the Na1 atoms. Coordination number 8 is observed for Na2. Both sodium sites are clearly distinguished by 23 Na MAS-NMR spectroscopy. Above 400 K the spectra reveal distinct chemical exchange effects, signifying sodium ion hopping between these two sites. At the same time static 19 F NMR spectra indicate pronounced motional narrowing effects in this temperature region. The nearly invariant 69 Ga MAS-NMR spectra suggest that any reorientational motion involving the GaF 6 3− ions (if present) occurs with preservation of the center of mass of these octahedra.

This work presents and disentangles the temperature dependent optical properties of the red-emitting phosphor Na 3 GaF 6 :Mn 4+ . Moreover, crystal field and Racah parameters were investigated. It was proven that the material is suitable for the application in warm white LEDs due to its high quantum yield of about 83%, little thermal quenching of the photoluminescence up to 410 K, high lumen equivalent of about 220 lm/W, and strong absorption at 450 nm. In addition, different DFT approaches were used to investigate its band structure. The calculated data were compared to those obtained experimentally. Red phosphor spectra were calculated to evaluate the suitability of red line-emitting phosphors for the application in warm white emitting pcLEDs. Finally, warm white emitting LEDs comprising Na 3 GaF 6 :Mn 4+ were constructed in order to show the potential of Na 3 GaF 6 :Mn 4+ serving as a red component in phosphor blends for future warm white pcLEDs.

The crystal structures of 6-methyl-2-ethyl-3-hydroxypyridiniun nitrate (C 8 H 12 NO)NO 3 ( I ) and fumarate (C 8 H 12 NO) 2 C 4 H 2 O 4 ( II ) were solved and refined from X-ray single crystal diffraction data (CuKα, ( I ) a =4.6477(2), b =14.5906(9), c =14.5551(8) Å, β =99.100(4)°, space group P 2 1 /c , Z=4, R p / R wp =0.033/0.047; ( II ) a =8.8293(3), b =13.4268(5), c =8.3893(3) Å, β =96.303(3)°, space group P 2 1 / c , Z=2, R p / R wp= 0.034/0.049). Both structures are built of infinite chains along ac diagonal of the unit cells formed by hydrogen bonding between the hydroxypyridium cation and the corresponding anion. Each fumarate anion is linked to four hydroxypyridium cations while nitrate anion is connected with two hydroxypyridium cations only leaving one oxygen atom in the nitrogen group isolated.

Trimethylglycine and betainium class ionic liquids were employed in synthesizing six uranyl-betaine coordination complexes: [(μ 2 -(CH 3 )N 2 C 3 H 3 (CH 2 COO)) 2 (UO 2 (Cl)((CH 3 )N 2 C 3 H 3 (CH 2 COO))) 2 ] 2[N(SO 2 CF 3 ) 2 ] ( 1 ), [K][UO 2 (Cl) 3 ((CH 3 ) 3 NCH 2 COO)] ( 2 ), [(CH 3 ) 3 NCH 2 COOH][UO 2 (Cl) 3 ((CH 3 ) 3 NCH 2 COO)]⋅H 2 O ( 3 ), [LiUO 2 (μ 2 -(CH 3 ) 3 NCH 2 COO) 4 ] 3[N(SO 2 CF 3 ) 2 ] ( 4 ) {(μ 2 -(CH 3 ) 3 NCH 2 COO)UO 2 (NO 3 ) 2 ((CH 3 ) 3 NCH 2 COO)} 2 UO 2 (NO 3 ) 2 , UO 2 (NO 3 ) 2 (H 2 O) 2 ⋅H 2 O ( 5 ), and UO 2 (Cl) 2 (H 2 O)(μ 2 -(CH 3 ) 3 NCH 2 COO) ( 6 ). These complexes expound upon the variability of mono carboxyl-functionalized uranyl coordination complexes, providing an enhanced framework for investigations into the structural chemistry of analogous actinyl systems.