10.1021/jp061200l.s002 Andrew S. Ichimura Andrew S. Ichimura Rui H. Huang Rui H. Huang Qingshan Xie Qingshan Xie Philip Morganelli Philip Morganelli Amy Burns Amy Burns James L. Dye James L. Dye One-Dimensional Zigzag Chains of Cs<sup>-</sup>:  The Structures and Properties of Li<sup>+</sup>(Cryptand[2.1.1])Cs<sup>-</sup> and Cs<sup>+</sup>(Cryptand[2.2.2])Cs<sup>-</sup> American Chemical Society 2006 field calculations electron density cryptand chain structure 7 Å. Optical wave functions van der Waals radii 1 D zigzag chain structures structure model magic angle Ab initio multiconfiguration electron density difference map alkali metal anions 133 Cs NMR chemical shifts cesium atoms zigzag chain Li anisotropic reflectivities ceside trimer resonance measurements 2006-06-29 00:00:00 Dataset https://acs.figshare.com/articles/dataset/One_Dimensional_Zigzag_Chains_of_Cs_sup_sup_The_Structures_and_Properties_of_Li_sup_sup_Cryptand_2_1_1_Cs_sup_sup_and_Cs_sup_sup_Cryptand_2_2_2_Cs_sup_sup_/3073669 The crystal structure and properties of lithium (cryptand[2.1.1]) ceside, Li<sup>+</sup>(C211)Cs<sup>-</sup>, are reported. Li<sup>+</sup>(C211)Cs<sup>-</sup> is the second ceside and third alkalide with a one-dimensional (1D) zigzag chain of alkali metal anions. The distance between adjacent Cs<sup>-</sup> anions, 6 Å, is shorter than the sum of the van der Waals radii, 7 Å. Optical, magic angle spinning NMR, two-probe alternating and direct current conductivity, and electron paramagnetic resonance measurements reveal unique physical properties that result from the overlap of adjacent Cs<sup>-</sup> wave functions in the chain structure. The properties of cesium (cryptand[2.2.2]) ceside, Cs<sup>+</sup>(C222)Cs<sup>-</sup>, were also studied to compare the effects of the subtle geometric changes between the two 1D zigzag chain structures. Li<sup>+</sup>(C211)Cs<sup>-</sup> and Cs<sup>+</sup>(C222)Cs<sup>-</sup> are both low-band-gap semiconductors with anisotropic reflectivities and large paramagnetic <sup>133</sup>Cs NMR chemical shifts relative to Cs<sup>-</sup>(g). An electronic structure model consistent with the experimental data has sp<sup>2</sup>-hybridized Cs<sup>-</sup> within the chain and sp-hybridized chain ends. Ab initio multiconfiguration self-consistent field calculations on the ceside trimer, Cs<sub>3</sub><sup>3-</sup>, support this model and indicate a net bonding interaction between nearest neighbors. The buildup of electron density between adjacent Cs<sup>-</sup> anions is visualized through an electron density difference map constructed by subtracting the density of three cesium atoms from the short Cs<sub>3</sub><sup>3-</sup> fragment.