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The π-conjugated [C 3 H 6+ x N 6 ] x + ( x = 0-3) cations are good functional groups, which are widely employed in the preparations of nonlinear optical (NLO) and birefringent materials due to their high hyperpolarizability and optical anisotropy. In this paper, the first melamine hydroxyborate [C 3 H 7 N 6 ] 3 [B 3 O 5 (OH) 2 ] ( MelBO-I ) was synthesized by the boric acid melting method under the molar ratio of H 3 BO 3 :C 3 H 6 N 6 = 1:1. MelBO-I ( P 2 1 / c ) exhibits a two-dimensional (2D) {[C 3 H 7 N 6 ] 3 [B 3 O 5 (OH) 2 ]} ∞ layer composed of [C 3 H 7 N 6 ] + cations and [B 3 O 5 (OH) 2 ] 3- anions interconnected via hydrogen bonds. MelBO-I exhibits significant birefringence (Δ n = 0.286@546 nm). Under the molar ratio of H 3 BO 3 /C 3 H 6 N 6 = 3:1, [C 3 H 8 N 6 ] 4 [B 12 O 19 (OH) 6 ] ( MelBO-II ) was isolated. In MelBO-II ( P 2 1 ), highly polymerized [B 12 O 19 (OH) 6 ] 8- groups form a 3D network through hydrogen bonding, featuring 1D tunnels of 8-membered and 16-membered rings filled by [C 3 H 8 N 6 ] 2+ cations. MelBO-II is the first noncentrosymmetric (NCS) bifunctional melamine borate with a moderate SHG response (0.4 × KDP) and large birefringence (Δ n = 0.285@546 nm). The results indicate that incorporating [C 3 H 6+ x N 6 ] x + ( x = 0-3) cations into borate can effectively induce birefringence. A high concentration of boric acid promotes the formation of large boric acid cluster anions and facilitates the transformation from the CS to NCS structure.

The first examples of alkali metal selenite sulfates, namely, Na 8 (SeO 3 )(SO 4 ) 3 (1), Na 2 (H 2 SeO 3 )(SO 4 ) (2), and K 4 (H 2 SeO 3 )(HSO 4 ) 2 (SO 4 ) (3), were successfully synthesized by hydrothermal reactions. Their structures display three different zero-dimensional configurations composed of isolated sulfate tetrahedra and selenite groups separated by alkali metals. Na 8 (SeO 3 )(SO 4 ) 3 (1) features a noncentrosymmetric structure, while Na 2 (H 2 SeO 3 )(SO 4 ) (2) and K 4 (H 2 SeO 3 )(HSO 4 ) 2 (SO 4 ) (3) are centrosymmetric. Powder second-harmonic-generation measurements revealed that Na 8 (SeO 3 )(SO 4 ) 3 (1) shows a phase-matchable SHG intensity about 1.2 times that of KDP. UV-vis-NIR diffuse reflectance spectroscopic analysis indicated that Na 8 (SeO 3 )(SO 4 ) 3 (1) has a short UV cutoff edge and a large optical band gap, which makes it a possible UV nonlinear optical material. Theoretical calculations revealed that the birefringence of Na 8 (SeO 3 )(SO 4 ) 3 (1) is 0.041 at 532 nm, which is suitable for phase-matching condition. This work provides a good experimental foundation for the exploration of new UV nonlinear crystals in an alkali metal selenite sulfate system.

Exploring new material systems is a highly significant task in the field of inorganic chemistry. A new mixed-valent selenium compound, Hg 3 Se(SeO 3 )(SO 4 ), was successfully synthesized through in situ reactions. This compound exhibits a novel three-dimensional structure composed of Hg 3 Se(SO 4 ) layers bridged by SeO 3 trigonal pyramids. It is the first structure containing (SeO 3 ) 2- , (SO 4 ) 2- , and Se 2- simultaneously. In addition, Hg 3 Se(SeO 3 )(SO 4 ) possesses a wide bandgap (3.5 eV), moderate birefringence (Cal:0.064@546 nm, Exp:0.069@546 nm), a high laser-induced damage threshold (23.35 MW cm -2 ), and a wide transmittance window (0.28-6.6 μm). Our work demonstrates that mixed-valent (+4, -2) selenite selenide can be potential optical materials for the mid-infrared region.

Two new mixed-anion cerium iodates, namely, Ce(IO 3 ) 3 F and Ce(IO 3 ) 2 (NO 3 ), have been rationally designed through the integration of hybrid anionic functional building blocks (FBBs). The structure of Ce(IO 3 ) 3 F features a novel [Ce(IO 3 ) 3 F] bilayer, and the material exhibits large birefringence (0.225 @546 nm). The structure of Ce(IO 3 ) 2 (NO 3 ) features [Ce 3 (IO 3 ) 6 ] 3+ triple layers that are further linked by planar NO 3 - units. Ce(IO 3 ) 2 (NO 3 ) shows a moderate SHG response (1 × KDP) and a high laser-induced damage threshold value (22 × AgGaS 2 ). This work demonstrates that the rich coordination geometries of cerium cations facilitate tuning of the structures of related compounds through modulating anionic FBBs.

Organic-inorganic hybrid nonlinear optical (NLO) materials are highly anticipated because of the integration of both merits of the organic and inorganic moieties. Herein, the 2-pyrimidinone cation (C 4 H 5 N 2 O) + has been incorporated into the iodate system to form two polymorphic organic-inorganic hybrid iodates, namely, α- and β-(C 4 H 5 N 2 O)(IO 3 )·HIO 3 . They crystallize in different polar space groups ( Ia and Pca 2 1 ), and their structures feature one-dimensional (1D) chain structures composed of (C 4 H 5 N 2 O) + cations, IO 3 - anions, and HIO 3 molecules interconnected via hydrogen bonds. α- and β-(C 4 H 5 N 2 O) (IO 3 )·HIO 3 exhibit strong and moderate second-harmonic-generation (SHG) responses of 6.4 and 0.9 × KH 2 PO 4 (KDP), respectively, the same band gaps of 3.65 eV, and high powder laser-induced damage threshold (LIDT) values [51 and 57 × AgGaS 2 (AGS)]. The results of theoretical calculations revealed that the large SHG effect of α-(C 4 H 5 N 2 O)(IO 3 )·HIO 3 originated from the IO 3 and HIO 3 groups. This work indicates that (C 4 H 5 N 2 O) + is a potential group for designing new NLO materials with brilliant optical performances.

The exploration of novel inorganic tellurites is significant because of their promising applications in nonlinear-optical materials and birefringent materials. Herein, three new aluminum/gallium tellurites, namely, NaAl(Te 4 O 10 ) ( 1 ), AgAl(Te 4 O 10 ) ( 2 ), and K 2 Ga 2 (HTe 6 O 16 )(HTeO 3 ) ( 3 ), have been successfully obtained by mild hydrothermal reactions. The isostructural compounds 1 and 2 contain the Te 3 O 8 trimer, while compound 3 contains an unprecedented Te 6 O 16 hexamer. Notably, all three compounds exhibit large birefringence values of over 0.1 at 532 nm, which are currently the largest reported birefringence values among tellurium(IV) oxides without additional anionic groups.

The first carbonatotellurites, AKTeO 2 (CO 3 ) (A = Li, Na), have been successfully synthesized by using boric acid as the mineralizer. AKTeO 2 (CO 3 ) (A = Li, Na) crystallize in the monoclinic space group P 2 1 / n (no. 14), and their structures exhibit the novel zero-dimensional (0D) [Te 2 C 2 O 10 ] 4- clusters, in which two [TeO 4 ] 4- groups form a [Te 2 O 6 ] 4- dimer via edge-sharing, with each side of the dimer attached by a [CO 3 ] 2- group via a Te-O-C bridge. The alkali metal cations occupy the voids between the 0D clusters and maintain the charge balance. The ultraviolet-visible-near-infrared diffuse reflectance spectra show that the short absorption cut-off edges of LiKTeO 2 (CO 3 ) (LKTC) and NaKTeO 2 (CO 3 ) (NKTC) are 248 and 240 nm, respectively, and LKTC exhibits the largest experimental band gap (4.58 eV) among all of the tellurites containing the π-conjugated anionic groups reported. Theoretical calculations revealed that they exhibit moderate birefringences of 0.029 and 0.040@1064 nm, respectively.

A new polar hafnium iodate, CsHfF 4 (IO 3 ), was successfully designed and synthesized by integrating fluorinated hafnium-oxygen polyhedra (HfF 6 O 2 ) and IO 3 - anionic functional groups. Owing to the weak electronic effect of Hf 4+ and the bond-network-induced out-of-center distortion of the HfF 6 O 2 dodecahedra, CsHfF 4 (IO 3 ) achieves a good balance between a strong second-harmonic-generation effect (3.5 × KH 2 PO 4 ) and a rather large band gap (4.47 eV), which is the largest among the d 0 transition-metal iodates. In addition, CsHfF 4 (IO 3 ) possesses a wide transparent region (0.27-9.9 μm), a large birefringence for phase-matching (0.161), and a high laser-induced damage threshold (55.41 MW cm -2 , 26 × AgGaS 2 ) and is nonhygroscopic. This work indicates that the integration of mixed-ligand acentric coordination polyhedra and functional groups containing lone electron pairs is an effective strategy for developing novel inorganic nonlinear-optical materials with balanced overall properties.

Two new borogermanate/borosilicate fluorides, namely, NaBa 3 [M 2 B 7 O 16 (OH) 2 ]F 2 (M = Ge, Si), have been successfully synthesized through a conventional mild hydrothermal method. They represent the first examples of mixed alkali and alkaline-earth borogermanate/borosilicate fluorides. NaBa 3 [M 2 B 7 O 16 (OH) 2 ]F 2 (M = Ge, Si) crystallize in the space group of C 2/ c , and their structures feature a unique 3D anionic framework composed of [B 7 O 16 (OH) 2 ] 13- polyanions corner-sharing with SiO 4 or GeO 4 tetrahedra, forming 1D 10-membered-ring tunnels along the b axis, which are filled by Na + , Ba 2+ , and F - ions. UV-vis-near-IR absorption spectra identify the title compounds possessing short deep-ultraviolet absorption edges (below 200 nm), while their birefringences were calculated to be 0.021 and 0.016 at 1064 nm, respectively. Optical property, thermal stability, and theoretical calculations have also been conducted on NaBa 3 [M 2 B 7 O 16 (OH) 2 ]F 2 (M = Ge, Si).

Herein, a new chiral compound with short Ag-Ag distances, namely, β-Ag 4 P 2 S 7 ( P 3 1 21), has been discovered by a solid-state method. Density functional theory (DFT) calculations show that both α and β phases exhibit suitable band gaps, low reduction potentials, and large visible-light absorption coefficients, as well as excellent band edges for carrier separation, suggesting their promising application in photocatalytic hydrogen production.

The first examples of zirconium fluoroantimonites, namely, K 3 ZrF 4 (SbF 4 )(SbF 5 ) and K 8 (ZrF 6 )(Sb 2 Zr 2 F 20 ), have been successfully synthesized by facial hydrothermal reactions. K 3 ZrF 4 (SbF 4 )(SbF 5 ) features a unique 1D (ZrSb 2 F 13 ) 3- double-chain structure, while K 8 (ZrF 6 )(Sb 2 Zr 2 F 20 ) displays a special 0D construction composed of Zr 2 Sb 2 F 20 tetranuclear clusters and isolated ZrF 6 octahedra. The two fluorides can exhibit a broad transparency range with almost no absorption peaks from ultraviolet to near-IR. For K 8 (ZrF 6 )(Sb 2 Zr 2 F 20 ), a phase transformation was found before decomposition. The band structures, density of states, and linear-optical properties for the title compounds were also obtained.

Two new indium iodate-nitrates, In(IO 3 ) 2 (NO 3 ) ( 1 ) and [In(IO 3 )(OH)(H 2 O)](NO 3 ) ( 2 ), were rationally designed through the integration of hybrid anionic functional units. They exhibit large birefringences ( 1 , 0.269; 2 , 0.188, at 532 nm) and wide band gaps ( 1 , 4.08 eV; 2 , 4.39 eV), which is attributed to the synergistic effect of two types of birefringence-active units, namely, lone-pair IO 3 and π-conjugated NO 3 anionic groups. Through the substitution of OH and H 2 O of 2 with IO 3 , the hydrogen bonds of 2 are eliminated and the birefringence of 1 is greatly enhanced, highlighting the intriguing role of isovalent substitution in the discovery of fascinating optical materials.

A new phase-matchable nonlinear-optical material, Na 3 Ti 3 O 3 (SeO 3 ) 4 F, has been achieved by a facile hydrothermal reaction. The anionic skeleton displays a honeycombed 3D structure with Ti 6 Se 6 12-member polyhedral ring tunnels along the c axis. Na 3 Ti 3 O 3 (SeO 3 ) 4 F presents a strong second-harmonic-generation (SHG) response of about 6 × KDP, which is twice that of its isostructural Ag compound. Interestingly, the band gap of Na 3 Ti 3 O 3 (SeO 3 ) 4 F is also broader than that of the isomorph. Also, the powder laser-induced damage threshold of Na 3 Ti 3 O 3 (SeO 3 ) 4 F is even 5.5 times larger than that of Ag 3 Ti 3 O 3 (SeO 3 ) 4 F. Theoretical calculations revealed that the fully filled Ag 4d and empty Ag 5s states have made the difference in the band gap and SHG response of the two isostructural compounds. Our work has provided a practical way of improving the SHG efficiency and band gap simultaneously, which is usually considered to be a pair of negatively correlated parameters.

Explorations of new types of borates are important because of their promising application in diverse fields. A new bismuth-containing boroselenite, Bi 2 [B 2 (SeO 3 ) 6 ], has been obtained through high-temperature solid-state reaction in a closed system. Bi 2 [B 2 (SeO 3 ) 6 ] possesses a zero-dimensional [B 2 (SeO 3 ) 6 ] 6- anionic group that does not belong to any types of reported boroselenites. Besides, Bi 2 [B 2 (SeO 3 ) 6 ] is the first boroselenite with lone-pair electrons containing a metal ion as the countercation. More interestingly, on the basis of the first-principles calculations, this compound displays a large birefringence (0.090) at 1064 nm.

Two new antimonous phosphates, namely Ba 3 Sb 2 (PO 4 ) 4 and Cd 3 Sb 2 (PO 4 ) 4 (H 2 O) 2 , have been successfully prepared through mild hydrothermal reactions. Ba 3 Sb 2 (PO 4 ) 4 features a 1D [Sb(PO 4 ) 2 ] 3- chain structure separated by Ba 2+ cations while Cd 3 Sb 2 (PO 4 ) 4 (H 2 O) 2 presents a 2D [Sb(PO 4 ) 2 ] 3- layered structure with Cd 2+ located at the interlayer space. The [Sb(PO 4 ) 2 ] 3- chain in Ba 3 Sb 2 (PO 4 ) 4 is the first example of 1D antimonous phosphate structure, and Cd 3 Sb 2 (PO 4 ) 4 (H 2 O) 2 represents the first d 10 transition metal antimonous phosphate. Based on UV-vis-NIR spectra, both Ba 3 Sb 2 (PO 4 ) 4 and Cd 3 Sb 2 (PO 4 ) 4 (H 2 O) 2 can display large optical band gaps (4.30 and 4.36 eV, respectively). But their transparent ranges are quite different because of the coordination water of Cd 3 Sb 2 (PO 4 ) 4 (H 2 O) 2 (500-2000 and 500-1300 nm for Ba and Cd compounds). The anhydrous Ba 3 Sb 2 (PO 4 ) 4 shows high thermal stability in the nitrogen atmosphere (900 °C). Because of the incorporation of the lone pair cation of Sb(III), the birefringence of Ba 3 Sb 2 (PO 4 ) 4 and Cd 3 Sb 2 (PO 4 ) 4 (H 2 O) 2 has been enhanced to 0.086 and 0.053 at 532 nm, respectively.

The search of novel second-harmonic generation crystals in gallium selenite systems results in three new compounds of MGa 2 (SeO 3 ) 4 (M = Sr, Pb) and BiGa(SeO 3 ) 3 . The isostructural MGa 2 (SeO 3 ) 4 (M = Sr, Pb) are centrosymmetric ( P 1̅, no. 2). The structures represent a complicated three-dimensional skeleton containing two different types of Ga 4 Se 4 8-member polyhedral ring tunnels with the counter cations located at the broad ones. When the divalent counter cations were substituted by a trivalent lone pair cation of Bi(III), a novel noncentrosymmetric compound of BiGa(SeO 3 ) 3 was achieved. BiGa(SeO 3 ) 3 displays a 3D gallium selenite framework with 1D bismuth oxide chains filling in the 12-member polyhedral ring tunnels. Frequency doubling measurements showed that BiGa(SeO 3 ) 3 presented an apparent SHG signal comparable to the commercial KDP and can realize phase matching. The lone pair anionic groups of SeO 3 2- made the major contribution according to the SHG density analyses. BiGa(SeO 3 ) 3 exhibits a wide transparent range and large optical bandgap (3.90 eV). The laser-induced damage threshold of BiGa(SeO 3 ) 3 was estimated to be 98.68 MW/cm 2 , about 44 × AGS.

Two new barium polyiodate compounds in the alkali-earth system, namely, HBa 2.5 (IO 3 ) 6 (I 2 O 5 ) ( Fdd2) and HBa(IO 3 )(I 4 O 11 ) ( P1̅) have been obtained through hydrothermal reaction. Interestingly, the structures of both compounds feature different polyiodate groups, i.e., I 2 O 5 and I 4 O 11 groups. HBa 2.5 (IO 3 ) 6 (I 2 O 5 ) can be depicted as an alternative stacking of two-dimensional (2D) [Ba 4 (IO 3 ) 8 (I 2 O 5 ) 2 ] and [Ba(IO 3 ) 4 (I 2 O 5 ) 2 ] 2- layers with the I 2 O 5 and IO 3 group serving as linkers. HBa(IO 3 )(I 4 O 11 ) can be depicted as a 3D network with 2D [Ba(I 4 O 11 )] layers being interconnected by IO 3 groups. The 0D I 4 O 11 polyiodate group can be seen also viewed as formed by an I 3 O 8 group further corner-sharing with an IO 3 group or an I 2 O 5 group further corner-sharing with two IO 3 groups. Powder second harmonic generation (SHG) measurements show that HBa 2.5 (IO 3 ) 6 (I 2 O 5 ) crystals display a moderate SHG efficiency of ∼1.6 times that of KH 2 PO 4 (KDP) and are phase-matchable. Optical properties measurements, thermal analyses, and laser damage threshold (LDT) measurements have been performed. Results of theoretical calculation show that the formation of I 4 O 11 2- is thermodynamically much easier than I 3 O 8 - and I 2 O 5 , because of the lower reaction energy. Our studies shed light on exploring alkali-earth polyiodates as potential NLO materials.

Three new acentric Sc-based borates, K 6 ACaSc 2 (B 5 O 10 ) 3 (A = Li, Na, Li 0.7 Na 0.3 ; space group R32), have been obtained and characterized. They are isostructural, and all exhibit three-dimensional [Sc 2 (B 5 O 10 ) 3 ] 9- anionic architecture composed of B 5 O 10 clusters and ScO 6 octahedra with the alkali- and alkaline-earth-metal cations occupying the cavities and keeping the charge balance. These compounds possess moderate second-harmonic-generation (SHG) responses (∼0.2×β-BaB 2 O 4 at 532 nm and ∼0.4×KH 2 PO 4 at 1064 nm) with phase-matching abilities and importantly display short cutoff edges below 200 nm. Furthermore, the relationship between the crystal structure and the SHG property has also been discussed based on the theoretical calculations.

Three new cadmium(II) tartratoborates, namely, Cd 5 [(C 4 H 2 O 6 ) 2 B] 2 (H 2 O) 8 ·3H 2 O (1), K 2 Cd 4 [(C 4 H 2 O 6 ) 2 B] 2 (H 2 O) 2 (2), and Li 0.92 K 1.08 Cd 1.5 [(C 4 H 2 O 6 ) 2 B](H 2 O) 2 (3), have been successfully synthesized by the hydrothermal method. Compounds 1-3 belong to centric C2/ c, acentric Pc, and the polar C2, respectively. Through based on the same hybrid borate-tartrate [(C 4 H 2 O 6 ) 2 B] 5- anions, they exhibit different structures. The [(C 4 H 2 O 6 ) 2 B] 5- anion is composed of two tartrate anions and a B(OH) 4 - unit. Compound 1 features a novel 3D network formed by 2D {Cd 3 [(C 4 H 2 O 6 ) 2 B] 2 (H 2 O) 2 } 4- anionic layers and [Cd 2 O 10 ] dimers, forming tunnels of large 14-MRs which are filled by the non-coordination water molecules. Compound 2 has a characteristic 3D network based on {Cd 2 [(C 4 H 2 O 6 ) 2 B]} - units interlinked via carboxylate groups, forming tunnels of 11-MRs, half of which stuffed with the K + ions. Compound 3 features 2D {Cd 4 [(C 4 H 2 O 6 ) 4 B]} 3+ layers which are separated by K/Li ions. Luminescent studies suggest that they emit blue light. Compounds 2 and 3 display phase-matchable second harmonic generation signs of about 3.2× and 1.5× KH 2 PO 4 , respectively.

We adopted a chemical substitution strategy to design a particular anionic structure with large optical anisotropy in phosphate. Specifically, we replaced one O 2- in Ba 3 P 3 O 10 Cl by two Cl - , leading to the formation of a new compound of BaPO 3 Cl ( P2 1 / c). Notably, this compound is the first metal phosphate chloride featuring infinite [PO 3 ] ∞ chains, and it displays good chemical and thermal stability, as well as a short UV cutoff edge (<200 nm) and relatively large birefringence.

A new nonlinear optical material, the first fluoride selenite nitrate PbCdF(SeO 3 )(NO 3 ), was successfully synthesized by traditional solid state reactions. This compound crystallizes in the polar space group of Pca2 1 , and its structure features a novel 2D layered structure consisting of 1D lead nitrate chains and 2D cadmium selenite layers. PbCdF(SeO 3 )(NO 3 ) exhibits a phase-matchable SHG efficiency of about 2.6 times that of KDP and a wide band gap of 4.42 eV. Its laser damage threshold was measured to be 135.6 MW/cm 2 , which is comparative to that of the reported Li 7 (TeO 3 ) 3 F with a short ultraviolet cutoff edge. Theoretical calculation confirmed that the synergistic effects of all the four functional units make PbCdF(SeO 3 )(NO 3 ) a remarkable SHG material.

Here, the combination of the strong electropositive lithium and the most electronegative fluorine with the TeO 3 group afforded the first lithium fluoride tellurite, namely, Li 7 (TeO 3 ) 3 F (P6 3 ), which was synthesized by solid-state reactions. Its structure features a novel three-dimensional anionic framework of [Li 7 O 9 F] 12- composed of LiO 3 F and LiO 4 tetrahedra with one-dimensional hexagonal tunnels of 12-membered rings along the c-axis, filled by the "isolated" ψ-TeO 3 tetrahedra. Notably, this compound displays the largest band gap of 4.75 eV among all of the non-centrosymmetric metal-tellurites reported so far, as well as strong second harmonic generation (SHG) responses (3 × KH 2 PO 4 @1064 nm, 0.2 × β-BaB 2 O 4 @532 nm) and a large laser damage threshold (73 × AgGaS 2 ). Furthermore, theoretical calculations reveal that the LiO 4 and LiO 3 F tetrahedra also contribute significantly to the SHG response (∼30%).

Partial substitution of iodate anions in La(IO 3 ) 3 by OH - or NO 3 - anion led to acentric La 3 (IO 3 ) 8 (OH) and chiral La(IO 3 ) 2 (NO 3 ). The structure of La 3 (IO 3 ) 8 (OH) can be seen as a complex three-dimensional (3D) network composed of two-dimensional [La 3 (IO 3 ) 2 (OH)] 6+ cationic layers that are further bridged by remaining iodate anions, or alternatively as a 3D network composed of one-dimensional [La 3 (IO 3 ) 6 (OH)] 2+ cationic columns being further interconnected by additional iodate anions, while the structure of La(IO 3 ) 2 (NO 3 ) can be seen as a novel 3D structure with planar NO 3 groups serving as linkage between the [La 3 (IO 3 ) 6 ] 3+ triple layers. Compared to La(IO 3 ) 3 , both compounds show considerably wide band gaps and enhanced thermal stability. La(IO 3 ) 2 (NO 3 ) shows a moderate second harmonic generation (SHG) response of ∼0.6 times that of KDP (KH 2 PO 4 ), a wide band gap of 4.23 eV, and a high LDT value (22 × AgGaS 2 ). Optical property measurements, thermal analysis, as well as theoretical calculations on SHG origin, were performed. It can be deduced that partial substitution of iodate anions can be a facile route to design new noncentrosymmetric metal iodates with novel structure and potential application.

Two new barium gold iodates, namely, BaAu(IO 3 ) 5 and HBa 4 Au(IO 3 ) 12 , have been prepared. BaAu(IO 3 ) 5 crystallizes in the polar space group Pca2 1 , whereas HBa 4 Au(IO 3 ) 12 crystallizes in the centrosymmetric space group P2 1 /c. BaAu(IO 3 ) 5 consists of unique polar [Au(IO 3 ) 4 ] - anions whose four iodate groups are located at both sides of the AuO 4 plane and the polarity points in the [001̅] direction. BaAu(IO 3 ) 5 displays strong second-harmonic-generation (SHG) effects about 0.6KTiOPO 4 (KTP) and is phase-matchable. Thermal properties, optical spectra analyses, and theoretical calculations are also reported.

The first examples of mixed-anion lanthanide galloborates, namely, Ln2Ga[B3O6(OH)]2[B7O9(OH)2](CH3CO2)2 [Ln = Y (1), Sm (2), Eu (3), Gd (4), Dy (5)], have been obtained through hydrothermal synthesis. The title compounds are isomorphic and belong to monoclinic space group C2/c (No. 15). Their structures possess [B7O13(OH)2] borate layers further bridged with [B3O7] clusters to give a three-dimensional (3D) borate framework displaying two types of rhombus-like B14O14 14-membered-ring (14-MR) channels along the b axis. The Ga(3+) ions are octahedrally coordinated and located at one end of the B14O14 14-MR channels, forming small tunnels of B7Ga 8-MRs, which are filled by the Ln(III) ions. The Ln ions and Ga cations are further held together by bridging acetate anions. It is worth noting that in these compounds there are two different types of borate clusters and two types of anions that are uncommon in the borates reported. Luminescent studies revealed the characteristic emission bands of Ln ions for compounds 2-5, and the luminescent lifetimes are 3.6, 0.86, and 3.05 ns for compounds 2, 3, and 5, respectively. Magnetic measurements suggest that there are antiferromagnetic interactions between magnetic centers for compounds 2-5.

A new series of platinum iodates, namely, α-(H3O)2Pt(IO3)6, β-(H3O)2Pt(IO3)6, and A2Pt(IO3)6 (A = Na, K, Rb, Cs), have been synthesized. Interestingly, among these six stoichiometrically identical compounds, α-(H3O)2Pt(IO3)6 is polar, whereas other compounds are nonpolar and centrosymmetric. They all consist of zero-dimensional [Pt(IO3)6](2-) molecular units separated by H3O(+) or A(+) cations. All of the lone electron pairs of the IO3(-) groups are aligned and almost point to one direction for α-(H3O)2Pt(IO3)6, whereas IO3(-) groups are located trans to each other in other compounds. The material, α-(H3O)2Pt(IO3)6, exhibits very strong second harmonic generation (SHG) effects, approximately 1.2 × KTiOPO4 (KTP), and is phase-matchable. Thermogravimetric analysis, elemental analysis, infrared spectra, UV-vis spectra, nonlinear optical properties, and theoretical calculations are also reported.

The first example of SHG crystal in the metal bromates containing π-conjugated planar triangle systems, namely, Pb4(OH)4(BrO3)3(NO3), was successfully synthesized via the hydrothermal method. Furthermore, a single crystal of centrosymmetric Pb8O(OH)6(BrO3)6(NO3)2·H2O was also obtained. Both compounds contain similar [Pb4(OH)4] cubane-like tetranuclear clusters, but they display different one-dimensional (1D) chain structures. Pb4(OH)4(BrO3)3(NO3) features a zigzag [Pb4(OH)4(BrO3)3](+) 1D chain, while Pb8O(OH)6(BrO3)6(NO3)2·H2O is composed of two different orthogonal chains: the linear [Pb4(OH)4(BrO3)2](2+) 1D chain along the b-axis and the zigzag [Pb4O2(OH)2(BrO3)4](2-) 1D chain along the a-axis. The NO3 planar triangles of the compounds are all isolated and located in the spaces of the structures. Pb4(OH)4(BrO3)3(NO3) exhibits the first example of SHG crystal in the metal bromates with π-conjugated planar triangle. The second-harmonic generation (SHG) efficiency of Pb4(OH)4(BrO3)3(NO3) is approximately equal to that of KDP and it is phase-matchable. Dipole moment and theory calculations indicate that BrO3, NO3, and PbO4 groups are the origin of its SHG efficiency, although some of the contributions cancel each other out.

Standard high-temperature solid-state reactions of NaCl, Nb2O5, and SeO2 resulted in two new sodium selenites containing a second-order Jahn-Teller (SOJT) distorted Nb(5+) cation, namely, Na2Nb4O7(SeO3)4 (P1̅; 1) and NaNbO(SeO3)2 (Cmc21; 2). Compound 1 exhibits an unusual 3D [Nb4O7(SeO3)4](2-) anionic network composed of 2D [Nb4O11(SeO3)2](6-) layers which are further bridged by additional SeO3(2-) anions via corner sharing; the 2D [Nb4O11(SeO3)2](6-) layer is formed by unusual quadruple [Nb4O17](14-) niobium oxide chains of corner-sharing NbO6 octahedra being further interconnected by selenite anions via Nb-O-Se bridges. The polar compound 2 features a 1D [NbO(SeO3)2](-) anionic chain in which two neighboring Nb(5+) cations are bridged by one oxo and two selenite anions. The alignments of the polarizations from the NbO6 octahedra in 2 led to a strong SHG response of ∼7.8 × KDP (∼360 × α-SiO2), which is the largest among all phases found in metal-Nb(5+)-Se(4+)/metal-Nb(5+)-Te(4+)-O systems. Furthermore, the material is also type I phase matchable. The above experimental results are consistent with those based on DFT theoretical calculations. Thermal stabilities and optical properties for both compounds are also reported.

Two new mixed metal fluoride carbonates, KCdCO3F and K2Pb3(CO3)3F2, have been synthesized by solvothermal and solid-state techniques. KCdCO3F crystallizes in the acentric nonpolar space group P6̅m2, and its structure features a three-dimensional anionic framework in which the CdCO3 layers are further interconnected by bridging F(-) anions with the negative charge balanced by K(+) cations. K2Pb3(CO3)3F2 crystallizes in the centrosymmetric space group P63/mmc, and its structure exhibits a layered anionic skeleton featuring corner-shared PbO6F and PbO6F2 polyhedra. UV-vis diffuse reflectance spectroscopy studies show that the short-wavelength absorption edges of KCdCO3F and K2Pb3(CO3)3F2 are 227 and 287 nm, respectively. The second harmonic generation (SHG) measurement reveals that KCdCO3F is a phase-matchable material for generation of doubled-frequency light at both 532 and 266 nm, with a large SHG response of approximately 5.2 times that of KH2PO4 (KDP) at 532 nm and a moderate SHG response of approximately 0.75 times that of β-BaB2O4 (BBO) at 266 nm. Therefore, it is a promising UV material for fourth harmonic generation on a 1064 nm Q-switched Nd:YAG laser.

The first examples of lanthanide borate-acetate mixed anion compounds, namely, Ln2(CH3CO2)2[B5O9(OH)]·H2O (Ln = La 1; Ce 2; Pr 3), were synthesized under hydrothermal conditions. These compounds are isostructural and crystallize in polar space group Cc. They display a unique three-dimensional (3D) framework built by a 3D network of lanthanide borate further decorated by acetate anions. The borate anion exhibits a 2D layer in the ac plane with large 9-member rings (MRs) which are filled by lanthanide(III) ions into a {Ln[B5O9(OH)]}(-) 2D layer. Adjacent {Ln[B5O9(OH)]}(-) layers are bridged by remaining lanthanide (III) ions to form a 3D network of lanthanide borate. It is noteworthy that Ln2(CH3CO2)2[B5O9(OH)]·H2O (Ln = La 1; Ce 2; Pr 3) can be changed into Ln2(CH3CO2)2[B5O9(OH)] (Ln = La 4; Ce 5; Pr 6) under heating at 500 K. Compounds 1-4 display moderate SHG signals of about 2.0, 1.0, 1.4, and 2.5 times that of KH2PO4, respectively, and they are phase matchable. Their SHG responses mainly arise from the synergistic polarization effects of both asymmetric borate clusters and π-conjugated CH3COO(-) anions.

Two new cesium selenites containing TaO6 or TiO4F2 octahedra, namely, Cs(TaO2)3(SeO3)2 (1) and Cs(TiOF)3(SeO3)2 (2), have been prepared using standard high temperature solid-state method and hydrothermal reaction, respectively. Compound 1 crystallizes in P3̅m1 and features an unusual [(TaO2)3(SeO3)2](-) sandwich-like double layer in which two [Ta(1)O3(SeO3)](3-) layers are bridged by central Ta(2)O6 octahedra via corner-sharing, whereas Cs(TiOF)3(SeO3)2 with a polar space group P63mc features an interesting hexagonal tungsten oxide (HTO) layered topology and presents a strong second harmonic generation (SHG) of about 5 × KDP (KH2PO4), which is much larger than those of A(VO2)3(QO3)2 (A = K, Tl, Rb, Cs, or NH4; Q = Se, Te) with a similar HTO layered structure. Cs(TiOF)3(SeO3)2 is also type-I phase matching. The SHG of above-mentioned HTO materials can be enhanced greatly with the replacement of VO6 octahedra by TiO4F2 octahedra. Furthermore, thermal stabilities, UV-vis diffuse reflectance spectra, infrared spectra, relationship between crystal structure and SHG, and theoretical calculations were also reported.

The first examples of metal borotellurates, namely, Na2RE2TeO4(BO3)2 (RE = Y, Dy-Lu) have been prepared by using solid-state reactions. They possess similar structures and crystallize in space group P21/c (No. 14). These compounds feature a novel [RE2TeO4(BO3)2](2-) 3D network structure composed of linear [TeO4(BO3)2](8-) anions interconnected by RE(3+) ions with the voids of the network filled by the Na(+) ions. They exhibit high thermal stability (higher than 800 °C). Results of magnetic measurements on Dy, Ho, and Er compounds indicate that they display weak antiferromagnetic interaction between RE(III) centers. Luminescent studies show that Na2Er2TeO4(BO3)2 has a strong emission at 1.562 μm with a wide fwhm (70 nm) and moderate lifetime (0.18 ms), whereas Na2Yb2TeO4(BO3)2 has a strong NIR region emission around 1.02 μm. Furthermore, UV-vis-NIR absorption spectra, infrared spectra, and DFT calculations for the Y compound as a representative were also accomplished.

Hydrothermal reactions of PbCO3 (or PbCl2), V2O5, and SeO2 in KOH solution or HF solution resulted in three new lead(II)-vanadium(V) mixed-metal selenites, namely, Pb4V6O16(SeO3)3(H2O) (1), Pb2VO2(SeO3)2Cl (2), and PbVO2(SeO3)F (3). Compounds 1 and 2 are polar (space group P21), whereas compound 3 is centrosymmetric (space group Pbca). Compound 1 displays an unusual [V6O16(SeO3)3](8-) anionic chain, which is composed by a 1D [V4O12](2-) anionic chain that is further decorated by dimeric [V2O6(SeO3)3](8-) units via corner-sharing. Compound 2 features two types of 1D chains, a cationic [Pb2Cl](3+) chain and a [VO2(SeO3)2](3-) anionic chain, whereas compound 3 contains dimeric [V2O4(SeO3)2F2](2-) units. The powder second-harmonic-generating (SHG) measurements indicate that compound 1 shows a weak SHG response of about 0.2 × KDP (KH2PO4) under 1400 nm laser radiation. Thermal stability and optical properties as well as theoretical calculations based on density functional theory methods were also performed.

Two new boroantimonates, namely, KSbB2O6 and BaSb2B4O12, have been successfully synthesized through high-temperature solid state reactions. Their structures feature two types of novel anionic 3D frameworks composed of 1D chains of corner-sharing SbO6 octahedra that are interconnected by B2O5 groups. The 1D chains of corner-sharing SbO6 octahedra in polar KSbB2O6 (space group Cc) are extended along the c-axis, whereas those in the centrosymmetric BaSb2B4O12 (space group C2/c) are propagated along the [101] direction. The K(+) ions are located at the 1D tunnels of the anionic frameworks along both b- and c-axis, whereas Ba(2+) ions are located at the 1D tunnels of the anionic frameworks along both the a- and c-axis. KSbB2O6 is a polar material that displays weak SHG response, whereas BaSb2B4O12 is centrosymmetric and not SHG active. Studies on their optical properties, thermal stability, and band structure calculations based on DFT methods have been also performed.

Two new alkaline-earth strontium borogermanates, namely, SrGe2B2O8 and Sr3Ge2B6O16, have been successfully synthesized through high-temperature solid state reactions. They represent the first examples of strontium borogermanates. SrGe2B2O8 crystallized in space group Pnma, and its structure features a novel three-dimensional [Ge2B2O8](2-) framework composed of alternative linkages of the B2O7 and Ge2O7 dimeric units with one-dimensional (1D) tunnels of eight-membered rings (MRs) along the b axis that are filled by the Sr(2+) cations. Sr3Ge2B6O16 is isostructural with Ba3Ge2B6O16 and crystallizes in centrosymmetric space group P1. Its structure features a two-dimensional layer that is composed of circular B6O16 clusters and GeO4 tetrahedra that are interconnected via corner sharing, forming 1D four- and six-MR tunnels along a axis. Sr(1) cations are located in the six-MR tunnels, whereas Sr(2) cations are located in the interlayer space. Studies of their optical properties and thermal stability as well as band structure calculations based on density functional theory methods have been also performed.

The syntheses, crystal structures, and characterizations of a series of monovalent metal gold(III) iodates, namely, α-NaAu(IO3)4, β-NaAu(IO3)4, RbAu(IO3)4, α-CsAu(IO3)4, β-CsAu(IO3)4, and AgAu(IO3)4 are reported. Their structures feature Au(IO3)4(-) anions that are separated by alkali metal ions or silver(I) ions. The Au(IO3)4(-) anions in the polar α-NaAu(IO3)4, RbAu(IO3)4, and α-CsAu(IO3)4 are polar with all four iodate groups being located only above (or below) the AuO4 square plane (cis- configuration). α-NaAu(IO3)4, RbAu(IO3)4, and α-CsAu(IO3)4 display moderate strong Second-Hamonic Generation (SHG) responses of 1.17 ×, 1.33 ×, and 1.17 × KTP (KTiOPO4), respectively, and all three materials are type-I phase-matchable. The Au(IO3)4(-) anions in centrysymmetric β-NaAu(IO3)4, β-CsAu(IO3)4, and AgAu(IO3)4 are nonpolar with the four iodate groups of the Au(IO3)4(-) anion being located both above and below the AuO4 square plane (trans- configuration). IR and UV spectra, luminescent and ferroelectric properties have also been measured. Theoretical calculations of their optical properties based on density functional theory (DFT) methods were performed by using the CASTEP total-energy code.

Using lead metaborate as starting material, by only adjusting pH values of the reaction systems, a series of lead(II) borates were obtained in high yields. The new polar material, namely, Pb2B3O5.5(OH)2 (1), crystallizes in the noncentrosymmetric space group Pnn2 of the orthorhombic system. Its structure features a novel three-dimensional (3D) anionic network with large 14 member rings (MRs) tunnels composed of unique one-dimensional (1D) chains and dimeric B2O7 fragments, both of which are built up from solely BO4 tetrahedra, and the Pb(2+) cations are located at the above 14-MRs tunnels. The synergistic effect of the stereoactive lone-pairs on Pb(2+) cations in 1 produces a strong SHG response of ∼3× KDP (KH2PO4) which is type I phase-matchable. The first example of lead(II) borate nitrate, namely, [Pb3(B3O7)](NO3) (2), crystallizes in space group Pnma, and its structures features a 3D lead(II) borate cationic network structure in which (B3O7)(5-) anions are bridged by lead(II) cations, the nitrate anions are isolated, and located at the small voids of the cationic network. Thermal stability and optical properties as well as theoretical calculations based on density functional theory (DFT) methods were also performed.

A new alkali-metal borogermanate with noncentrosymmetric structure, namely, Cs2GeB4O9, has been discovered, and a large crystal with dimensions of 20 × 16 × 8 mm(3) has been grown by a high-temperature top-seeded solution method using Cs2O-B2O3 as a flux. The compound crystallizes in the tetragonal space group I4 with a = b = 6.8063(2) Å, c = 9.9523(7) Å, V = 461.05(4) Å(3), and Z = 2. It features a three-dimensional anionic open framework based on GeO4 tetrahedra and B4O9 clusters that are interconnected via corner-sharing, forming one-dimensional channels of nine-/ten-membered rings along the a and b axes, which are occupied by Cs(+) cations. Cs2GeB4O9 exhibits a very high thermal stability with a melting point of 849 °C, and it possesses a short-wavelength absorption edge onset at 198 nm determined by UV-vis transmission spectroscopy measurements on a slab of polished crystal. Powder second-harmonic generation (SHG) measurement on sieved crystals reveals that Cs2GeB4O9 is a type I phase-matchable material with a strong SHG response of about 2.8 × KH2PO4. The preliminary investigation indicates that Cs2GeB4O9 is a new promising second-order nonlinear-optical crystalline material.

The synthesis, crystal and electronic structures, and optical properties of the first zinc(II) vanadium(V) iodate, namely, Zn2(VO4)(IO3), are reported. Zn2(VO4)(IO3) crystallizes in the noncentrosymmetric (NCS) and polar space group Pc (No. 7) with a = 5.2714(8) Å, b = 10.0402(11) Å, c = 5.5070(8) Å, β = 101.326(10)°, and Z = 2. It displays a novel three-dimensional (3D) network structure composed of ZnO5, ZnO6, VO4, and IO3 polyhedra. One-dimensional (1D) chains of edge-sharing ZnO5 polyhedra and 1D chains of corner-sharing ZnO6 octahedra along the c-axis are interconnected via corner-sharing into a two-dimensional (2D) zinc oxide layer, and such layers are bridged by both VO4 tetrahedra and IO3 groups into a 3D network. The polarity in the structure is imparted by the alignment of the stereochemically active lone pairs of the iodate anions along the c-axis. The second harmonics generation (SHG) measurements on powder samples of Zn2(VO4)(IO3) under 1064-nm laser radiation revealed a large response of ∼6 × KDP, which is Type I phase-matchable. Thermal stability and optical properties, as well as theoretical calculations based on DFT methods, were also performed.

Three new galloborates, namely, GaB(5)O(8)(OH)(2)(en)(2)·H(2)O (1), LiGa(OH)(BO(3))(H(2)O) (2), and Rb(2)Ga(B(5)O(10))(H(2)O)(4) (3), have been synthesized by hydrothermal reactions. Compound 1 is the first example of a galloborate that contains an organic component. It crystallizes in space group P2(1)/c, and its crystal structure exhibits an infinite zigzag chain consisting of [B(5)O(8)(OH)(2)](3-) anions and GaO(2)N(4) octahedra interconnected via corner sharing. Compound 2 crystallizes in space group P31c with a layered structure composed of GaO(4), LiO(4), and BO(3) building units. Compound 3 belongs to chiral space group C222(1); the basic building blocks of the structure are the [B(5)O(10)](5-) cluster anion and GaO(4) tetrahedron, which are interconnected to form a three-dimensional network with tunnels of Ga2B6 eight-membered rings (8-MRs) which are filled by Rb(+) cations and lattice water molecules. Interestingly, Rb(2)Ga(B(5)O(10))(H(2)O)(4) displays a moderate second-harmonic generation (SHG) response comparable to that of KH(2)PO(4) (KDP), and it is phase matchable. Band structure and optical property calculations for Rb(2)Ga(B(5)O(10))(H(2)O)(4) based on DFT methods were also performed.

Two new acentric borogermanates, Ca(10)Ge(16)B(6)O(51) (Pba2) and Cd(12)Ge(17)B(8)O(58) (P4), have been successfully synthesized by high-temperature solid-state reactions of CaCO(3) (or CdCO(3)), GeO(2), and H(3)BO(3). Both structures display the same one-dimensional (1D) [Ge(4)O(12)](n) chains composed of GeO(4) tetrahedra and GeO(6) octahedra. In Ca(10)Ge(16)B(6)O(51), neighboring 1D [Ge(4)O(12)](n) chains are condensed into a two-dimensional (2D) [Ge(4)O(10.75)](n) layer via corner sharing, and such layers are further interconnected by "isolated" BO(4) tetrahedra and B(2)O(7) dimers into a three-dimensional (3D) framework, forming 1D tunnels of 5-, 6-, and 7-MRs along the c axis that are occupied by Ca(2+) cations. In Cd(12)Ge(17)B(8)O(58), neighboring 1D [Ge(4)O(12)](n) chains are interconnected into a [Ge(4)O(10.5)](n) open framework via corner sharing with large pores filled by big [Ge(B(2)O(7))(4)](28-) clusters, leading to formation of three types of 1D tunnels of 5-, 6-, and 7-membered rings (MRs) along the c axis which are occupied by the Cd(2+) cations. Both compounds are transparent in the range of 0.3-6.67 μm and exhibit very weak SHG responses.

Three novel rubidium borogermanates with three types of noncentrosymmetric structures, namely, RbGeB(3)O(7), Rb(2)GeB(4)O(9), and Rb(4)Ge(3)B(6)O(17), have been synthesized by high-temperature solid-state reactions in platinum crucibles. The structure of RbGeB(3)O(7) features a three-dimensional (3D) anionic framework composed of cyclic B(3)O(7) groups corner-sharing GeO(4) tetrahedra. The structure of Rb(2)GeB(4)O(9) shows a 3D anionic framework based on B(4)O(9) clusters connected by GeO(4) tetrahedra via corner sharing. The structure of Rb(4)Ge(3)B(6)O(17) is a novel 3D anionic framework composed of cyclic B(3)O(8) groups, Ge(2)O(7) dimers, and GeO(4) tetrahedra that are interconnected via corner sharing. Second harmonic generation (SHG) measurements indicate that RbGeB(3)O(7), Rb(2)GeB(4)O(9), and Rb(4)Ge(3)B(6)O(17) display moderate SHG responses that are approximately 1.3, 2.0, and 1.3 × KH(2)PO(4) (KDP), respectively, which are slightly smaller than those from theoretical calculations (about 3.7, 2.8, and 2.4 × KDP, respectively)., (© 2011 American Chemical Society)

Six new novel alkaline-earth metal vanadium(V) or vanadium(IV) selenites and tellurites, namely, Sr(2)(VO)(3)(SeO(3))(5), Sr(V(2)O(5))(TeO(3)), Sr(2)(V(2)O(5))(2)(TeO(3))(2)(H(2)O), Ba(3)(VO(2))(2)(SeO(3))(4), Ba(2)(VO(3))Te(4)O(9)(OH), and Ba(2)V(2)O(5)(Te(2)O(6)), have been prepared and structurally characterized by single crystal X-ray diffraction analyses. These compounds exhibit six different anionic structures ranging from zero-dimensional (0D) cluster to three-dimensional (3D) network. Sr(2)(VO)(3)(SeO(3))(5) features a 3D anionic framework composed of VO(6) octahedra that are bridged by SeO(3) polyhedra. The oxidation state of the vanadium cation is +4 because of the partial reduction of V(2)O(5) by SeO(2) at high temperature. Ba(3)(VO(2))(2)(SeO(3))(4) features a 0D [(VO(2))(SeO(3))(2)](3-) anion. Sr(V(2)O(5))(TeO(3)) displays a unique 1D vanadium(V) tellurite chain composed of V(2)O(8) and V(2)O(7) units connected by tellurite groups, forming 4- and 10-MRs, whereas Sr(2)(V(2)O(5))(2)(TeO(3))(2)(H(2)O) exhibits a 2D layer consisting of [V(4)O(14)] tetramers interconnected by bridging TeO(3)(2-) anions with the Sr(2+) and water molecules located at the interlayer space. Ba(2)(VO(3))Te(4)O(9)(OH) exhibits a one-dimensional (1D) vanadium tellurite chain composed of a novel 1D [Te(4)O(9)(OH)](3-) chain further decorated by VO(4) tetrahedra. Ba(2)V(2)O(5)(Te(2)O(6)) also features a 1D vanadium(V) tellurites chain in which neighboring VO(4) tetrahedra are bridged by [Te(2)O(6)](4-) dimers. The existence of V(4+) ions in Sr(2)(VO)(3)(SeO(3))(5) is also confirmed by magnetic measurements. The results of optical diffuse-reflectance spectrum measurements and electronic structure calculations based on density functional theory (DFT) methods indicate that all six compounds are wide-band gap semiconductors.

Three new novel palladium(II) iodates with square-planar PdO(4) units, namely, Pd(IO(3))(2), AgPd(IO(3))(3), and BaPd(IO(3))(4), have been successfully hydrothermally synthesized. They represent the first ternary and quaternary palladium(II) iodates and display three different structural types. Pd(IO(3))(2) exhibits a novel two-dimensional (2D) layered structure in which each PdO(4) square further connects with four neighboring ones by four bridging IO(3) groups. AgPd(IO(3))(3) exhibits a unique three-dimensional (3D) network based on unique one-dimensional (1D) [Pd(IO(3))(3)](-) anionic chains along the c-axis which are further interconnected by Ag(+) cations. BaPd(IO(3))(4) is isostructural with KAu(IO(3))(4), and its structure features zero-dimensional (0D) [Pd(IO(3))(4)](2-) anionic units that are interconnected by Ba(2+) cations. These materials can be polar or non-polar depending on the different alignments of the lone pairs of the I(V) atoms. Pd(IO(3))(2) and AgPd(IO(3))(3) are non-polar and centrosymmetric, hence not second-harmonic generation (SHG) active. BaPd(IO(3))(4) is polar and displays a moderate SHG response of about 0.4× KTP. Thermal analyses, optical, luminescent, and ferroelectric properties as well as electronic structure calculations have also been performed.

Systematic explorations of the new phases in the Pb(II)/Bi(III)-TM(d(0)/d(1))-Se(IV)-O systems by hydrothermal syntheses led to five new quaternary phases whose structures are composed of three different asymmetric building units, namely, Pb(2)V(V)(2)Se(2)O(11) (1), Pb(2)V(IV)(3)Se(5)O(18) (2), Pb(2)Nb(V)(2)Se(4)O(15) (3), Bi(2)V(V)(2)Se(4)O(16) (4), and Bi(2)Mo(VI)(2)Se(2)O(13) (5). The structure of 1 features a 3D network built by 1D anionic chains of [V(2)O(5)(SeO(3))(2)](4-) interconnected by Pb(2+) ions with six-membered-ring (MR) tunnels along the b axis. The structure of 2 features a 3D anionic framework composed of V(IV)O(6) octahedra corner-sharing with SeO(3) anions, with the Pb(2+) ions located at the resultant 8-MR tunnels. The oxidation state of the vanadium cation is 4+ due to the partial oxidation of V(2)O(3) by SeO(2) at high temperature. The structure of 3 features novel 1D double chains of [Nb(2)O(3)(SeO(3))(4)](4-) that are interconnected by Pb(2+) ions, forming a 3D network with 12-MR tunnels along the c axis. 4 features a 3D framework composed of 2D layers of [Bi(2)(SeO(3))(2)](2+) and 1D [(VO(2))(2)(SeO(3))(2)](2-) double chains. The structure of 5 features a 3D network composed of bismuth(III) selenite with large 10-MR tunnels along the a axis that are occupied by Mo(2)O(10) dimers. The results of optical diffuse-reflectance spectrum measurements and electronic structure calculations based on density functional theory methods indicate that all five compounds are wide-band-gap semiconductors. Luminescent property measurements for compounds 1-5 and magnetic measurements for compound 2 were also made.

Explorations of new second-order nonlinear optical (NLO) materials in the K(I)-M(II) -I(V)-O systems led to four novel mixed metal iodates, namely, K(2)M(IO(3))(4)(H(2)O)(2) (M = Mn, Co, Zn, Mg). The four compounds are isostructural and crystallize in space group I2 which is in the chiral and polar crystal class 2. Their structure features zero-dimensional {M(IO(3))(4)(H(2)O)(2)}(2-) anions that are separated by K(+) cations. The M(II) centers are ligated by two aqua ligands in trans fashion and four monodentate iodate anions. The K(+) cation is eight-coordinated by two iodate anions in bidentate chelating fashion and four other iodates in a unidentate fashion. Second harmonic generation (SHG) measurements indicate that K(2)Zn(IO(3))(4)(H(2)O)(2) and K(2)Mg(IO(3))(4)(H(2)O)(2) display moderate SHG responses that are approximately 2.3 and 1.4 times of KH(2)PO(4) (KDP), respectively, and they are also phase-matchable. The SHG response of K(2)Co(IO(3))(4)(H(2)O)(2) is much weaker (about 0.3 x KDP), and no obvious SHG signal was detected for K(2)Mn(IO(3))(4)(H(2)O)(2). Results of optical property calculations for the Zn and Mg phases revealed SHG responses of approximately 5.3 and 4.7 times of KDP, respectively, the order of Zn > Mg is in good agreement with the experiment data.

Two types of new organically templated mixed-metal sulfites, namely, [H(2)pip][NaZn(2)Cu(SO(3))(4)] (1) and [H(2)pip][CdCu(4)(SO(3))(4)] (2) (pip = piperazine), have been synthesized under hydrothermal conditions and structurally characterized. Both compounds exhibit a novel 3D mixed-metal inorganic framework with organic template molecules occupying the tunnels of the inorganic skeleton. Compound 1 features a 2D Zn(2)Cu(SO(3))(4)(3-) layer parallel to the ac plane in which the 1D chains of Zn(SO(3))(2)(2-) anions along the c axis are interconnected with the Cu(+) ions via Cu-S bonds. Neighboring Zn(2)Cu(SO(3))(4)(3-) layers are further interconnected by bridging Na(+) ions via Na-O-S bonds into a 3D network, forming 1D tunnels along the a axis which are occupied by the doubly protonated piperazine cations. Compounds 2 features a novel 3D inorganic framework of CdCu(4)(SO(3))(4)(2-) with 2D layers based on Cu(4)(SO(3))(4)(4-) cubanelike clusters. The cluster layers are further interconnected by Cd(II) ions, forming 1D tunnels of eight-membered rings along the c axis in which the piperazine template cations are located. Luminescent property measurements as well as band structure calculations based on density functional theory methods were also made.

The title three compounds have been synthesized by solid state reactions at high temperatures, with excess indium as flux, and structurally characterized by single-crystal X-ray diffraction studies. Eu(3)Co(2)In(15) forms a new structure type and crystallizes in the tetragonal space group P4/mbm (No. 127), whereas KM(2)In(9) (M = Co, Ni) in the BaFe(2)Al(9) type crystallizes in the hexagonal space group P6/mmm (No. 191). Their structures all feature a three-dimensional anionic framework based on 1D [MIn(6)] single cluster chains composed of face-sharing [MIn(9)] clusters. In Eu(3)Co(2)In(15), two adjacent [CoIn(6)] single cluster chains form a [Co(2)In(11)] double cluster chain via corner-sharing In atoms as well as In-In bonds; the latter chains are further interconnected by additional indium atoms via In-In bonds into a complicated 3D framework, forming two types of tunnels along the c-axis, which are filled by the europium atoms. In KM(2)In(9), the [MIn(6)] single cluster chains are directly interconnected via corner sharing and exo In-In bonds into a 3D framework with the K(+) ions encapsulated in the 1D tunnels along the c-axis. Band structure calculations of three compounds based on density functional theory methods indicate that all three compounds are metallic.