This article reviews different formulations of the thermodynamic cycles used for the prediction of pK_a values, their advantages, and disadvantages with special emphasis on the limitations resulting from the necessity of gas‐phase calculations, which allow introducing some difficult cases that motivated alternative strategies. Before introducing the protocols that do not consider gas‐phase calculations, the two current opinions available in the literature on the debate about the correct formalism for the calculation of free energies in solution are briefly introduced. Then, the isodesmic proton exchange reaction in solution is reviewed by analyzing its performance on difficult cases for thermodynamic cycles such as carbon acids and amino acids. The pK_a values predicted by the isodesmic reaction for common acid species are also reviewed to compare their accuracy results in relation with those of thermodynamic cycles. Linear regressions between experimental pK_a values and the calculated free energies obtained with the isodesmic reaction provide expressions for the dependence of the error in the calculated pK_as on the pK_a difference between the studied acid and the reference species. Finally, it is shown that linear regressions correct the calculated free energies of the isodesmic reaction, when high constant precision is required in a large pK_a range. The deviations from the expected behavior are equivalent to those reported previously for different pK_a calculation protocols and are determined by the inaccuracies of continuum solvent models on the interactions with ionic species.

A Ni-based 3D MOF, [Ni(3-bpd) ₂ (NCS) ₂ ] _n , where 3-bpd is 1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene, has been explored for simultaneous detection and removal of Hg ²⁺ in aqueous medium with excellent Hg uptake capacity.

A novel thiocyanate bridged 2D MOF, [CdL(μ-1,3-SCN)₂]_n, [HL = 2-(2-(ethylamino)ethyliminomethyl)-6-ethoxyphenol] has been synthesized and characterized by X-ray crystallography. The band gap of the synthesized material in the solid state has been determined by experimental measurements and compared with the theoretical value obtained from DFT calculations. For the first time, the single crystal X-ray crystallography of a MOF has been reported along with its applicability in photosensitive devices.

A Cd(II) based 2D metal–organic framework (MOF), [Cd(4-bpd)(SCN)₂]_n (1) where 4-bpd = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene, has been synthesized and characterized by standard methods including single crystal X-ray diffraction analysis. When it is sandwiched between ITO coated glass and Al, 1 shows interesting conduction properties. The I–V characteristics of the ITO/1/Al configuration measured in the dark and under illumination of incident light exhibit a highly non-linear rectifying behavior, which signifies its Schottky diode character. The conductivity of the configuration is 2.90 × 10⁻⁴ S m⁻¹ and 7.16 × 10⁻⁴ S m⁻¹ under dark and photoirradiation conditions, respectively. Different parameters have been analyzed and these indicate that 1 can be a promising candidate for light sensing electronic devices. This material has good sensitivity to the light source when switched on/off. Theoretical calculations have been performed to understand the reason for the enhancement of conductivity under illumination of incident light. It has been found that upon irradiation, slight changes in the bond distances of 4-bpd in 1 occur. These changes are related to the considerable decrease in the energy needed for the allowed electronic transition. This may influence the increase of conductivity along with other factors.