Establishing high performance ultraviolet (UV) nonlinear optical (NLO) selenite crystals with well‐balanced properties is very challenging attributable to their strong absorption for UV light. Here a rare‐earth selenite, Sc(HSeO3)3, with excellent UV NLO properties is introduced. Sc(HSeO3)3 crystallizing in the polar NCS space group, Cc, features a 3D archetiture built up by interconnected ScO6 octahedra and HSeO3 groups. The crystal exhibits remarkably well‐balanced UV‐NLO functionality, namely, the shortest absorption edge (214 nm) among NLO‐active selenites, wide bandgap (5.28 eV), large phase‐matchable SHG response (5 × KDP), and sufficiently large birefringence (cal. 0.105 @1064 nm). Detailed DFT calculations have been performed to elucidate the structure–property relationships. This work provides a new example of discovering novel UV NLO selenite materials.

A series of Eu-doped Zintl compounds belonging to the Ca5–x–y Yb x Eu y Al2Sb6 (x = 0, 1.12; 0 ≤ y ≤ 0.63(2)) system have been successfully synthesized by both the arc-melting and the molten Pb-flux methods. All of the five title compounds initially crystallized in the Ca5Ga2As6-type phase (space group Pbam, Z = 2, Pearson code oP26) and maintained their original structure even after the post-heat treatment, unlike the recently reported n-type Zintl analogues in the Ca5–x–y Yb x RE y Al2Sb6 (RE = Pr, Nd, Sm) systems, which underwent a phase transition from the Ca5Ga2As6-type to the Ca5Al2Bi6-type phase after annealing. This research aimed to understand the origin of the structural preference of the title Ca5–x–y Yb x Eu y Al2Sb6 system, whether it was affected by the valence electron count or the cationic size. Electrical transport property measurements showed an increase in electrical conductivities and a decrease of Seebeck coefficients for Ca4.89(1)Eu0.11Al2Sb6, Ca4.82(1)Eu0.18Al2Sb6, and Ca4.62(1)Eu0.38Al2Sb6, compared to the parental compound Ca5Al2Sb6. Hole effect measurements proved that these changes should be attributed to the reduced carrier concentration and enhanced carrier mobility. The comprehensive density functional theory calculations including electron density map analysis for the hypothetical model Ca4.5Eu0.5Al2Sb6 revealed that the polarity between Al and Sb forming the anionic frameworks decreased as the Eu-dopants were introduced, which eventually affected the carrier mobility in the anionic frameworks. Thermal conductivity measurements proved that the Eu-doping successfully lowered the lattice thermal conductivity because of the enhanced atomic disordering. The magnetization measurements for Ca4.37(2)Eu0.63Al2Sb6 showed a typical Curie–Weiss behavior with weak antiferromagnetic nearest-neighbor interactions with θp = −5.07 K.

Five novel Zintl phase solid solutions in the Ba1–x Sr x Zn2–y Cd y Sb2 (0 ≤ x ≤ 0.13(1); 0 ≤ y ≤ 0.32(2)) system were successfully synthesized by the molten Pb metal-flux method, and the powder X-ray diffraction and single-crystal X-ray diffraction analyses proved that all five title compounds adopted the BaCu2S2-type phase having the orthorhombic Pnma space group (Z = 4, Pearson code oP20) with five crystallographically independent atomic sites. The previously studied BaCu2S2-type antimonides demonstrated a limited tolerance for doping in contrast to the CaAl2Si2-type antimonides. To understand the relatively narrower phase width and limited dopability of the title BaCu2S2-type phase than the CaAl2Si2-type phase in the overall Ba1–x Sr x Zn2–y Cd y Sb2 system, the radius ratio of cations and anionic elements r +/r – for two structure types were thoroughly investigated. For the first time, the r +/r – ratio was identified as a critical factor for the phase selectivity: (1) r +/r – > 1 favored the BaCu2S2-type phase, and (2) r +/r – < 1 favored the CaAl2Si2-type phase. We also revealed the structural transformation mechanism from the more widely observed CaAl2Si2-type phase to the title BaCu2S2-type phase as the relatively larger cationic elements were introduced to the system. A series of DFT calculations using the three hypothetical models indicated that a resonance peak near E F in the density of states curves was descended from the relatively flat band structure at several special symmetry points rationalizing the enhanced Seebeck coefficients of Ba0.94(1)Sr0.06Zn1.86(3)Cd0.14Sb2 and Ba0.96(1)Sr0.04Zn1.68(2)Cd0.32Sb2. Electron localization function analysis rationalized the correlation between the polarity change of anionic Zn/Cd–Sb bonds and the charge carrier mobility on the anionic frameworks. Temperature-dependent thermoelectric properties were studied for the four title compounds, and the results proved that the Sr and Cd doping in the title Ba1–x Sr x Zn2–y Cd y Sb2 system successfully enhanced the ZT values through the increased Seebeck coefficients and the reduced total thermal conductivities.

A series of Yb-substituted Zintl phases in the Ca 3−x Yb x AlSb 3 (0 ≤ x ≤ 0.81(1)) system has been synthesized by initial arc melting and post-heat treatment, and their isotypic crystal structures were characterized by both powder and single crystal X-ray diffraction analysis. All four title compounds adopted the Ca 3 AlAs 3 -type structure (space group Pnma, Pearson code oP28, Z = 4). The overall structure can be described as a combination of the 1-dimensional (1D) infinite chain of ∞ 1 [Al(Sb 2 Sb 2/2 )] formed by two vertices sharing [AlSb 4 ] tetrahedral moieties and three Ca 2+ /Yb 2+ mixed sites located in between these 1D chains. The charge balance and the resultant independency of the 1D chains in the title system were explained by the Zintl-Klemm formalism [Ca 2+ /Yb 2+ ] 3 [(4b-Al 1− )(1b-Sb 2− ) 2 (2b-Sb 1− ) 2/2 ]. A series of DFT calculations proved that (1) the band overlap between the d-orbital states from two types of cations and the p-orbital states from Sb at the high symmetry Γ point implied a heavily doped degenerate semiconducting behavior of the quaternary Ca 2 YbAlSb 3 model and (2) the site preference of Yb for the M1 site was due to the electronic-factor criterion based on the Q values of each atomic site. The electron localization function calculations also proved that the two different shapes of lone pairs of the Sb atoms�the "umbrella-shape" and the "C-shape"�are determined by local geometry and the coordination environment on the anionic frameworks. Thermoelectric measurements of the quaternary title compound Ca 2.19(1) Yb 0.81 AlSb 3 showed an approximately two times larger ZT value than that of ternary Ca 3 AlSb 3 at 623 K due to increased electrical conductivity and ultralow thermal conductivity originated from Yb substitution for Ca.

Two positional isomers, 4-amino-3-methylpyridine and 3-amino-5-methylpyridine, produce 4-amino-3-methylpyridinium and 5-methylpyridin-3-aminium, respectively, under acidic conditions. The two protonated isomers create different hydrogen bonding networks, resulting in different coordination environments of the [MnX4]2– unit embedded in molecular compounds such as 4-amino-3-methylpyridinium manganese bromide, [(C6H9N2)2MnBr4] and 5-methylpyridin-3-aminium manganese bromide, [(C6H9N2)4MnBr4(H2O)·(MnBr4)]. Both compounds can be prepared using the slow evaporation method or mechanochemical synthetic procedures. Single-crystal structure analysis of [(C6H9N2)2MnBr4] and [(C6H9N2)4MnBr4(H2O)·(MnBr4)] revealed different manganese halide units, including tetrahedral and tetrahedral with distorted trigonal bipyramidal structures, which emit photoluminescence in the green (527 nm) and red (607 nm) regions, respectively. Electronic structure calculations were conducted to support the validity and interpretation of the UV–vis and photoluminescence (PL) spectral data. Thin films deposited using the [(C6H9N2)2MnBr4] precursor also exhibit PL properties. The diverse pseudo-three-dimensional networks can be constructed by using positional isomers with different hydrogen bonding pathways and π–π stacking of organic units, in which the design strategy successfully enables the tuning of various optical properties.