the several halogenometalates

compounds with various size of alkylammonium cation

exhibit numerous structural phase transitions related to reorientation

motion of alkyl chains

This phenomenon is called "hyperconjugation" and it is well-described in the literature

this tack place due to the electron flow in the aromatic ring when an electron done atom or groups added to the ring or the group that added not having an steric effect with the ring as in triethyl aniline in this compound the electron density decrease 

while in chloro or methyl benzene the density increase due to the ring absorb the electron to it 

 and so on