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Combining π‐conjugated and non‐π‐conjugated groups is an important strategy for synthesizing new nonlinear optical (NLO) crystals. However, the second harmonic generation (SHG) response and optical anisotropy can be limited by improper spatial alignment of these functional groups in the crystal structure. In this work, it is revealed that non‐π‐conjugated [NH2SO3] group acts as both hydrogen bond donor and acceptor, effectively regulating the 2D planar structure formed by π‐conjugated [C4N3H6] groups. The resulting organic–inorganic hybrid crystal C4N3H6SO3NH2 exhibits a strong SHG response (2.5 × KDP), large optical anisotropy (0.233@546 nm), and blue‐violet and green fluorescence near 360 and 520 nm, respectively. This work expands the methodology for creating new NLO crystals through organic–inorganic hybridization, while also showcasing the potential of C4N3H6SO3NH2 as a multifunctional optical material. [ABSTRACT FROM AUTHOR]

A new cesium hydroxyborate CsB3O4(OH)2, was designed and synthesized by a hydrothermal method. Remarkably, CsB3O4(OH)2 presents novel [B3O4(OH)2]∞ chains formed by [B3O4(OH)2] fundamental building blocks (FBBs). The report of less common [B3O4(OH)2] FBBs and [B3O4(OH)2]∞ chains in CsB3O4(OH)2 enriches the structural diversity of hydroxyborates. In addition, CsB3O4(OH)2 has a wide transparent window in the DUV spectral range and a large birefringence. [ABSTRACT FROM AUTHOR]

Two lead borate-nitrates Pb6O4(BO3)(NO3) and Pb6O2(BO3)2(NO3)F were obtained by the high-temperature flux method. Interestingly, their crystal structure consists of anion-centered [OPb4] tetrahedra and π-conjugated BO3 and NO3 units. The first principles calculations indicate that both compounds show large birefringence. [ABSTRACT FROM AUTHOR]

With the advancement of laser technology, searching for new nonlinear optics (NLO) active units is necessary for designing NLO materials with excellent performance. In this study, an amino substitution strategy is proposed to explore new planar π‐conjugated groups as functional building units (FBUs) for NLO and birefringent materials. Accordingly, a new NLO‐active molecule melem C6N7(NH2)3 is identified, which is characterized by significant polarization anisotropies and large hyperpolarizabilities. Subsequently, C6N7(NH2)3·H3PO4 is screened out and successfully synthesized through a simple aqueous method. The compound exhibits a strong second harmonic generation (SHG) response of 8.9 times that of KDP and a large birefringence of 0.609 at 1064 nm. As far as is known, the calculated birefringence of C6N7(NH2)3·H3PO4 is the largest among the organic–inorganic hybrid crystals in which the birefringence originates from π‐conjugated groups. The theoretical computation supports that the amino (─NH2) substitution strategy is effective for designing and synthesis of materials with strong SHG response and large birefringence. [ABSTRACT FROM AUTHOR]