A new cadmium ( II ) coordination polymer with 1,4 - cyclohexanedicarboxylate acid and phenanthroline derivate: Synthesis and crystal structure

: A new Cd ( II ) coordination polymers, formulated as [ Cd ( 1,4 - chdc )( L )] n ( 1 ) ( L = 1 -( 1 H - imidazo [ 4,5 - f ][ 1,10 ] phenanthrolin - 2 - yl ) naphthalen - 2 - olligandsand1,4 - H 2 chdc = 1,4 - cyclohexanedicarboxylate acid ) , were successfully synthesized by using L ligand and 1,4 - H 2 chdc acid under hydrothermal conditions and characterized by single crystal X - ray elemental analyses, di ﬀ raction, and IR spec - troscopy. Each Cd ( II ) atom is a distorted pentagonal bipyr - amidal geometry connecting the deprotonated 1,4 - chdc anion to form a 2D layer, and a 2D layer is formed into a 3D supramolecular structure by the π – π stacking inter - actions between neighboring layers.

Over the past decades, more and more researchers have focused on the design and synthesis of coordination polymers, because of their unique structures and their potential applications in magnetism, fluorescence, biological, gas storage, and so forth (Guillem et al., 2012;Liu et al., 2021;Song et al., 2021;Wang et al., 2020;Yang et al., 2010).Many different factors such as solvent, organic ligands, temperatures, pH, metal ions, and non-covalent interactions (aromatic stacking interactions) have influence on the final structures and properties of coordination polymers (Li et al. 2021;Martin et al. 2008).So far, most of the coordination polymers have been constructed from carboxylic acid ligands, nitrogen-containing organic ligands, and transition metal ions through intermolecular interactions or coordination bonds (Shimomura et al., 2010;Tiwari et al., 2021;Zhang et al., 2021).Phenanthroline derivative ligands are the typical N-donor ligands, which could adopt diverse conformations in the coordination of the center metal (Ma et al., 2009).Phenanthroline derivatives are rigid structures due to their central ring resulting in the two N-atoms being held in juxtaposition; so they can coordinate with transition metal ions quickly (Hu et al., 2021;Llabrés i Xamena et al., 2008;Song et al., 2021;Wei et al., 2020).In our research, nitrogen-containing organic ligands formed the π-π stacking interactions, and the existences of these π-π stacking interactions contribute considerably to the stability of coordination polymers (Wang et al., 2011).

Experimental
All the starting materials used in the synthesis procedure were bought from the commercial companies (Shanghai Yiyan Biological Technology Co., Ltd and Tianjin Yuzhou Chemical Sales Co., Ltd, China).Elemental analyses for C, H, and N were performed on a PerkinElmer 240 CHN elemental analyzer (PerkinElmer, North Waltham, USA).IR spectrum was recorded on an Alpha Centaurt FT/IR Spectrophotometer (Mattson Technology, USA).

X-ray crystallography
Crystallographic data for 1 were collected at 298 (2) K on a Bruker-AXS Smart CCD diffractometer, with graphitemonochromatized Mo-Kα radiation (λ = 0.71073 Å) using the ϕ and ω scan technique.The crystal structures were resolved by direct methods using SIR2014 (Burla et al., 2015) and refined by full-matrix least-squares methods based on F 2 using SHELXL2018/3 program (Sheldrick, 2015).All the non-hydrogen atoms were treated anisotropically.The hydrogen atoms were set in calculated positions and refined as riding atoms.The cyclohexane ring of 1,4-chdc in 1 was disordered over two positions, the occupancies of the two orientations were refined with their sum set to equal 1. Detailed information about the crystallographic parameters are listed in

Figure 3 :
Figure 3: View of the 2D layer structure of 1 constructed by the 1,4-chdc and L ligands.

Figure 4 :
Figure 4: View of the π-π interactions between two L ligands of neighboring layers.

Table 2
Conflict of interest: Authors state no conflict of interest.Data availability statement: All data generated or analyzed during this study are included in this published article.