Polymorphism in the metal–organic hybrid (PhCH2NEt3)2[CoBr4]: Synthesis, crystal structures and physico-chemical characterizations

•X-Ray diffraction showed polymorphic structures.•Hydrogen bonds lead to three-dimensional architectures.•Thermal stabilities of the polymorphs were studied.•The optical properties indicate a possible semiconductor behavior.•The polymorphs show weak magnetic interactions and/or single ion anisotropy.