Synthesis, crystal structure and Hirshfeld surface analysis of aqua(3-methoxycinnamato-κO)bis(1,10-phenanthroline-κ2 N,N′)cobalt(II) nitrate

The title compound crystallizes in the triclinic space group P with a monomeric [Co(3-meo-cin)(phen)2(H2O)]+ cation and a nitrate anion (3-meo-cin = 3-methoxy cinnamic acid) in the asymmetric unit. The CoII ion is coordinated by four N atoms from two 1,10-phenanthroline ligands and two O atoms, the first from a methoxy cinnamate ligand and the second from a coordinated water molecule, forming a distorted octahedral geometry.


Chemical context
Cinnamic acid (3-phenyl-2-propenoic acid), a derivative of phenyl alanine, comprises a relatively large family of organic isomers (Ferenc et al., 2012;Madhurambal et al., 2010). Cinnamic acid and its derivatives exhibit biological activities (Rychlicka et al., 2021) including antibacterial (Sova, 2012), antifungal (Ruwizhi & Aderibigbe, 2020) and antiparasitic properties (Kanaani & Ginsburg, 1992) as well as a variety of pharmacological properties (Adisakwattana et al., 2008) including hepatoprotective , antimalarial (Wiesner et al., 2001), antioxidant (Natella et al., 1999), antitumoral (Ferenc et al., 2012), antihyperglycemic and antityrosinase activities (Lee, 2002). Cinnamic acid and related compounds have attracted particular attention over the last few decades, not only for their biological activities, but also for their carboxylate group. The popularity of such aromatic carboxylic acids as building blocks for generating metalorganic architectures can be explained by their coordination versatility and ability to act as multiple linkers (Lehleh et al., 2015;Gu et al., 2020), high thermal stability, tuneable deprotonation of -COOH groups, remarkable physicochemical properties, as well as the ability to function as hydrogen-bond donors and acceptors, thus facilitating the formation of intricate hydrogen-bonded networks (Gu et al., 2020;Zhang et al., 2019;Zhou et al., 2019). Furthermore, bipyridyl-like ligands such as 2,2 0 -bipyridine and 1,10-phenanthroline used as auxiliary ligands, are usually used in the formation of different complexes with a variety of transition metals, because of their versatile roles such as in analytical chemistry, in catalysis, in electrochemistry, in ring-opening metathesis polymerization and biochemistry (Lehleh et al., 2011). Additionally, the pyridine rings can not only interact with each other viastacking interactions, but also act as hydrogen-bond donors and acceptors (Cao et al., 2014;Hao et al., 2011;Lehleh et al., 2011).
In this context, we report the synthesis, structural characterization and Hirshfeld surface analysis of the title compound [Co(C 10 H 9 O 3 )(C 12 H 8 N 2 ) 2 (H 2 O)] NO 3 .

Structural commentary
The asymmetric unit of the title compound, illustrated in Fig. 1, consists of a Co II complex cation and one nitrate anion. The Co II ion is in a distorted octahedral geometry, coordinated by two 1,10-phenanthroline (phen) units through both N atoms in the usual bidentate manner, one water molecule and one 3-methoxy cinnamate in a monodentate fashion. The Co-N phen bond distances range from 2.1356 (16) to 2.1488 (17) Å , while the Co-O cin and Co-O water bond lengths are 2.0525 (13) and 2.1011 (17) Å , respectively. The axial bond angles around the Co II ions are in the range 166.30 (7)-173.94 (6) ( Table 1). The large deviation of the axial bond angles from an ideal octahedral geometry (180 ) clearly indicates that the coordination environment around the Co II ion is best described as distorted octahedral. The 3-methoxy cinnamate molecule shows disorder over two positions with occupancies of 0.735 (6) and 0.265 (6).

Supramolecular features
The structure presents extensive hydrogen bonding with numerical details given in An ellipsoid plot of the title compound showing the atom-labelling scheme with ellipsoids drawn at the 50% probability level and H atoms shown as small spheres of arbitrary radii.   (Fig. 2). The complex moieties are interconnected via moderate C-HÁ Á ÁO hydrogen bonds between the 1,10-phenanthroline unit and the coordinating O atom of the 3-meo cinnamate ligand of a neighbouring complex on one side and between the 1,10-phenanthroline molecules and the O atoms of the nitrate anions on the other side, generating supramolecular hydrogen-bonded chains along the c-axis direction (Fig. 2). The chains are linked through slippedstacking interactions with intercentroid distances ranging from 3.729 (2) to 3.891 (2) Å , the most significant being between the pyridyl rings containing phenanthroline atom N4 of each molecule [Cg4Á Á ÁCg4(1 À x, Ày, 1 À z) = 3.7998 (18) Å ], forming layers parallel to the bc plane (Fig. 3, Table 3).

(Hirshfeld surface analysis
To further characterize the intermolecular interactions in the title compound, we carried out a Hirshfeld surface (HS) analysis (Spackman & Jayatilaka, 2009) using Crystal Explorer 21 (Spackman et al., 2021) and generated the associated twodimensional fingerprint plots (McKinnon et al., 2007). The HS mapped over d norm in the range 0.5087 to +1.3878 a.u. is illustrated in Fig. 4 using colours to indicate contacts that are shorter (red areas), equal to (white areas), or longer than (blue areas) the sum of the van der Waals radii (Ashfaq et al., 2021). The red spots on the surface mapped over d norm (Fig. 4a) indicate the involvement of atoms in hydrogen-bonding interactions. The HS mapped over shape-index ( Fig. 4b) is used to check for the presence of interactions such as C-HÁ Á Á andstacking (Ashfaq et al., 2021). The existence of adjacent red and blue triangular regions around the aromatic rings confirms the presence ofstacking interactions in the title compound (Fig. 4b), and the curvedness plots ( Fig. 4c) show flat surface patches characteristic of planar stacking. The two-dimensional fingerprint plots provide quantitative information about the non-covalent interactions and the crystal packing in terms of the percentage contribution of the interatomic contacts (Spackman & McKinnon, 2002;Ashfaq et al., 2021). Crystal packing of the title compound showing the layers parallel to the bc plane formed by thestacking interactions between the pyridyl rings of the 1,10-phenanthroline units (blue and cyan). Hydrogen bonds are shown by dashed cyan lines. Table 3 stacking interactions (Å ).

Cg
Ring

Synthesis and crystallization
A mixture of Co(NO 3 ) 2 Á6H 2 O (0.240 g, 1 mmol), 3-methoxy cinnamic acid (0.178 g, 1 mmol), NaOH (0.04 g, 1 mmol) and 1,10-phen (0.180 g, 1 mmol) were dissolved in 10 mL of mixed solution (MeOH/H 2 O: 2/1) in a 20 mL Teflon-lined stainless steel reactor and heated to 393 K for 24 h. It was then allowed to cool to room temperature in a water bath. Green crystals suitable for X-ray analysis were obtained.

Aqua[3-(3-methoxyphenyl)prop-2-enoato-κO]bis(1,10-phenanthroline-κ 2 N,N′)cobalt(II) nitrate
Crystal data  Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.