C(NH2)3(I3O8)(HI3O8)(H2I2O6)(HIO3)4middot3H2O: An Unprecedented Asymmetric Guanidinium Polyiodate with a Strong Second- Harmonic-Generation Response and a Wide Band Gap

Herein, we report an unprecedented asymmetric guanidinium polyiodate, namely, C(NH2)3(I3O8)(HI3O8)(H2I2O6)- (HIO3)4 center dot 3H2O (1). The title compound was obtained via the hybridization of polyiodate anions and planar pi-conjugated C(NH2)3+; meanwhile, its strong second-harmonic-generation (SHG) response (2.1 x KDP, where KDP = KH2PO4) and wide band gap (3.89 eV) were mainly dominated by the synergy effect of the aforementioned structural units.