MS18-P12 Role of Size and Electronegativity of the Transition Metal Ion, on The High Pressure Behavior of Dimethyl Ammonium Metal FormatesDimethyl ammonium metal formates (DmAMF) are important metal organic framework compounds (MOF). Though, they have been extensively studied at low temperature, to perceive their ferroelectric transition due to H-bonding , thermal expansion properties, stress-strain dependence, magneto-electric tunability  etc., very few studies have been carried out on these materials at high pressure. As per our studies, application of pressure deforms the formate network. This results in the distortion of the cubo-octahedral cavities formed by it, leading to the structural phase transition . However, the role, of size and electronegativity of the transition metal ion, on this phase transition, has not been addressed so far.
We have studied the dependency of divalent metal ion on pressure evolution of DmAMF (M = Ni, Co, Mn, Cd). Our IR spectroscopic studies show that the framework structure of the formates with transition metal cations having smaller ionic radii [Ni2+(0.69Ao) < Co2+(0.745Ao) < Mn2+(0.83Ao) < Cd2+(0.95Ao)] distort at higher pressures and the degree of distortion is less than the formates with higher cationic radii. It was also observed that the lower flexibility of the formate network in these compounds can be attributed to the stronger metal-formate coordination bond. In addition, on application of pressure the CNC mode softens [Fig (c) & (d)] and some of the hydrogen bonds weaken [Fig (a) & (b)] in the formates having smaller ionic radii cations, indicating that the electronegativity of the metal ion plays a vital role in the high pressure behavior of the coordination and hydrogen bonds. This information can help us to design new MOF’s with tailored properties. Further results will be discussed.
 M. Mączka, A. Gągor, B. Macalik, A. Pikul, M. Ptak, and J. Hanuza, Inorg. Chem. 53, 457, 2014.
 W. Wang, L. Q. Yan, J. Z. Cong, Y. L. Zhao, F. Wang, S. -P. Shen, T. Zou, D. Zhang, S.G. Wang, X. F. Han & Y. Sun, Scie. Rep. 3, 2024, 2013
 Abhishek Chitnis, H. Bhatt, M. Maczka, M. N. Deo, Nandini Garg, (submitted to Inorganic Chemistry on 15 Feb 2018)
Keywords: MOF, High pressure, IR