Hybrid organic–inorganic halometallates, with different organic and inorganic components, can provide a wide array of tunable physical properties. While many optoelectronic phenomena are being explored, research on the mechanical properties of this class of materials, especially fracture toughness, is lacking, resulting in conclusions on material flexibility being drawn from their elastic modulus and hardness alone with an implicit assumption that these properties correlate with material flexibility. In this Letter, we report nanoindentation results on the elastic modulus, hardness, and fracture toughness of single crystal samples of hybrid organic–inorganic histammonium chlorozincate, HistZnCl4 along the [001] axis. We find that the elastic modulus is 12.078 ± 1.034 GPa, and the hardness is 0.611 ± 0.089 GPa. Moreover, the fracture toughness of this sample is measured to be 0.098 MPa m12. Although these materials have a hardness to modulus ratio similar to that of metals, they fracture like brittle materials, demonstrating the importance of conducting studies on a material fracture toughness before determining their applicability in flexible device applications.

Nucleophilic aromatic substitution (SNAr) reactions are exploited to prepare poly(arylene sulfide)s (PAS's) via the reaction of bis-thiolates and dibrominated pyromellitic diimide (PMDI) derivatives. Small-molecule model studies reveal the reaction is well-defined and proceeds in quantitative yield in practical times at room temperature. Variation in comonomer feed ratios allowed some control over target polymer molecular weights in the step polymerization, but control was likely limited by the relatively poor polymer solubility in the dipolar aprotic solvents typically employed to promote SNAr reactions. One substitution pattern produces a steric "pocket" around the PMDI units, inducing a peculiar solubility trend in halogenated solvents; that is, greatly reduced solubility in CHCl 3 relative to CH 2 Cl 2 and C 2 H 2 Cl 4 . One example small-molecule readily dissolves in CHCl 3 at room temperature, then rapidly grows poorly soluble crystals revealed by single-crystal XRD to contain CHCl 3 molecules in the steric pockets. Finally, the recently demonstrated depolymerization of phthalonitrile-based PAS's via ipso substitution with monothiolates as chain scission agents yields quantitative molecular weight reduction to monomeric species from the polymers reported here.

To provide new insights for understanding the influence of B site cations on the structure in chlorometallate materials of the form AB n+Cl n+2, we report novel organic–inorganic hybrid metallates (OIHMs) incorporating histammonium (HistNH3) dications and various transition-metal and main group B site cations. Single crystals of OIHMs with the basic formula (HistNH3M n+Cl n+2, M = Fe, Co, Ni, Cu, Zn, Cd, Hg, Sb, Sn, Pb, Bi) were grown and their structures characterized by single-crystal X-ray crystallography. HistNH3CoCl4, HistNH3ZnCl4, and HistNH3SbCl5 were crystallized in a non-centrosymmetric space group and were subsequently studied with piezoresponse force microscopy (PFM). While bulk measurements of crystals and poly(vinylidene difluoride) (PVDF)/metallate composite films exhibited low bulk response values, the surface-measured local response values using PFM were 5.17 pm/V for HistNH3CoCl4, 22.6 pm/V for HistNH3ZnCl4, and 2.9 pm/V for HistNH3SbCl5 compared with 2.50 pm/V for PVDF reference samples. The magnitudes of the d 33 coefficient, net dipole, and cation–Cl bond dipole obtained from the density functional theory calculations confirm the higher response in HistNH3ZnCl4 compared to HistNH3CoCl4. Density of states and crystal orbital Hamilton population analysis indicate that the higher net dipole in HistNH3ZnCl4 compared to HistNH3CoCl4 is due to the lower hybridization of the M–Cl bond.

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