Fingerprint Intermolecular Interactions of Sodium and Potassium Complexes

The complex of sodium and potassium salts is characterized by using UV-Visible, FT-IR, NMR, Singlecrystal X-ray diffraction, Hirshfeld surfaces, and Fingerprint plots. The crystal belongs to the monoclinic system and p121/n1, p21/n space group. The corresponding peaks for chlorine atoms are absent in the NMR spectra of the complexes. The small red spot in Hirshfeld surfaces indicates the presence of CH...π interactions in the sodium complex. Absence of Metal...Metal interactions were also observed in both sodium and potassium complex. Fingerprint plots of Hirshfeld surfaces were used to detect and examine the percentage of hydrogenbonding interactions.

spectra data were obtained from Bruker DRX -500 MHz spectrophotometers with (DMSO-d6) is used as a solvent and tetramethylsilane is used as the internal reference. A single-crystal X-ray diffraction study has the dimensions 0.15mm x 0.26mm x 0.28mm was used for structural determination. The frames have been integrated with the Bruker SAINT Software package by using a narrow-frame algorithm.

Thin Layer Chromatographic Studies
The study was carried out to check the purity of the isolated molecules. Silica gel was used as an adsorbent. The slurry of silica gel was made with chloroform and coated uniformly on a TLC plate. The complex solution was prepared in pure absolute ethanol and spotted on the plate. The eluent used was the mixture of tertiary butyl alcohol and ethyl acetate.

Crystal Structure of Sodium Salt
The amorphous solid of sodium salt is crystallized from ethanol. The sodium cations are bridged through an oxygen atom of 1-chloro-2, 4-dinitro benzene as shown in fig 1. In barbiturate residue bond lengths, bond angles are well-matched with that of barbiturate ion 2 and it shows the delocalization of negative charge. The crystal data represent selected bond angles, bond distances of sodium salt. According to X-ray crystallographic data, the isolated molecule is a monoclinic system. The unit cell parameters ﴾Table 1) having P121/n1 space group a=7.3269(5) Å, b=19.9241(13) Å, c=11.5431(9) Å, V=1665.1(2) Å 3 ; Z=4.

Crystal structure of potassium salt
The structure of the potassium complex with DNCB, the crystals have been confirmed based on unitcell contents. The crystal studies indicate that potassium cations are 8-coordinated and are bridged by an oxygen atom of 1,3-dimethyl barbituric acid ﴾Fig 2). The K-O bond length range is 2.778-3.8699 (Shrivastava & Speakman, 1961). The Single-crystal XRD results have shown that the potassium salt of the present investigation possesses an organometallic polymeric association. The crystal data represent selected bond distances, bond angles of potassium salt. The molecule is a monoclinic crystal system having a P21/n space group and cell parameters are a=11.3166(7) Å, b=7.2477 Å, c=20.3511(11) Å; Z=4 as shown in Table 2

UV-Visible Analysis
In the UV-Vis spectrum, the two peaks are formed with λmax values of 287.30nm, 484.34nm, and 245.93 nm, 446.86 nm ( The d norm parameter is based on di. di is the distance from the surface to the nearest atom in the molecule itself, de is the distance from the surface to the nearest atom in another molecule, and Van der Waals radii of the corresponding atoms ﴾ri Vdw and re Vdw ).
The d norm values are employing a red-blue-white color scheme, where red regions represent closer contacts and negative d norm value; blue regions represent longer contacts and a positive d norm value and white regions represent the distance of contacts exactly corresponding to the Van der Waals separation with d norm value of zero [6][7][8] . The negative d norm value indicates the sum of di and de is shorter than the sum of the relevant Van der Waals radii, which is considered to be the closest contact and is visualized as red color in the Hirshfeld surfaces. Hirshfeld surfaces also enabling rapid computation of molecular volume ﴾VH), surface area﴾SH) and two other descriptors of global shape also have been calculated i) globularity﴾G) and ii) asphericity ﴾Ω). Globularity 9 ﴾G) is a measure of the degree to which the surface area differs from that of a sphere of the same value volume. G will be 1.0 for a sphere, and progressively less than one becomes more structured. Asphericity ﴾Ω) 10,11 is a measure of anisotropy and when applied to the positions of atoms in the molecules. small red spots on surfaces indicate that C-H...π interactions. By using 2D fingerprint plots, many interactions can be separated from others that overlap in full fingerprint plots ﴾Fig 8). There is a C…C interaction of sodium salt ﴾2.1%). From this sodium salt, the O…H interactions exhibit a more significant contribution ﴾25.3%) compared to the total Hirshfeld surfaces. The N…O, C…N, N…H, and N…N hydrogen bonding interactions do not exhibit significant contributions of total Hirshfeld surfaces. Metal…Metal ﴾M…M) interactions are not observed in sodium complex ﴾Table 3). Globularity value of sodium salt is 0.670 ﴾Table 4) and then surface property statistics are listed ﴾Table 5).

CONCLUSION
A sodium and potassium salts of carbanionic sigma complexes were synthesized and confirmed from the single-crystal X-ray diffraction technique. Both salts are monoclinic. The Hirshfeld surface is visualized by intermolecular interactions. Various kinds of interactions are seen in Hirshfeld surface analysis. Fingerprint plots are confirm the types and quantities of interactions in these complexes. Metal…Metal interactions are absent in sodium and potassium complexes of Hirshfeld surfaces.