Novel Pb(II) Complexes: X-Ray Structures, Hirshfeld Surface Analysis and DFT Calculations

: Herein we report the synthesis and detailed structural characterization of two new centrosymmetric dinuclear coordination compounds of Pb(II) [Pb 2 L 2 (NCS) 4 ] ( 1 ) and [Pb 2 L 2 (NO 3 ) 4 ] · 2MeOH ( 2 ), using the organic ligand 1,2-diphenyl-1,2-bis((methyl(pyridin-2-yl)methylene)hydrazono)ethane ( L ). In both complexes, each subunit [PbLX 2 (X = NO 3 or NCS)] adopts a quasi-aromatic Möbius metal chelate structure. Each ligand L is coordinated in a tetradentate coordination mode to Pb(II), yielding the 12 π electron chelate ring via two pyridyl-imine units. In compound ( 1 ), the coordination sphere is completed by one disordered N,S-coordinated thiocyanate anion and two µ 1,1 -bridging N-coordinated thiocyanate anions. In compound ( 2 ), the coordination sphere of Pb(II) is completed by two monodentate and two bidentate nitrato ligands (two of them acting as bridging ligands). Crystal packing of both compounds is stabilized by intermolecular hydrogen bonds, intra- and intermolecular C–H ··· π interactions. The Hirshfeld molecular surfaces of ( 1 ) and ( 2 ) demonstrate that their packing is dominated by C–H ··· O / N / S interactions as well as by far less favored H ··· H contacts.


Introduction
The development of new ligands capable of trapping Pb(II) is of continuous interest [1]. The rich and versatile coordination chemistry of Pb(II) is related to its large size in combination with the presence of a 6s 2 electron pair, which can remain inert or stereoactive [2]. In fact, the coordination number usually ranges from four to nine. This extraordinary versatility has been exploited for the preparation of a variety of hybrid inorganic-organic polymers and complexes [3][4][5]. In spite of the negative implications of lead related to health and environmental issues, it is used for the production of materials with interesting properties like semiconductors, NLO (non-linear optical) and ferroelectric materials [6].

Reagents
All reactants were used as received without further purification. The ligand was synthesized following the protocol available in the literature [26].

Crystallography
Single crystal X-ray diffraction data was collected at 293(2)K by using a Bruker APEX-II CCD diffractometer (Bruker, Karlsruhe, Germany) with MoKα radiation (λ = 0.71073 Å). The Bruker SAINT [27] program was used for data reduction and absorption correction was performed through the multi-scan method [28]. The title structures were solved by direct method through the program SHELXS-14 [29] and then refined by SHELXL-18 [30]. The calculations were performed using the programs WinGX V2014.1 [31] and PLATON [32]. The details of crystal data and structure refinement factors are included in Table 1. CCDC 2005501-2005502 contain the crystallographic data. Table 1. Crystal data and structure refinement parameters for compounds (1) and (2).

Other Physical Measurements
Microanalyses were performed using a Heraeus CHN-O-Rapid analyser (Heraeus, Hanau, Germany). The FTIR spectra were recorded on a Bruker Tensor 27 FTIR spectrometer (Bruker, Karlsruhe, Germany).

Synthesis
Complexes were synthesized using a methodology consisting of the utilization of a branched tube as described in the literature [26]. A suspension of L (0.222 g) and Pb(NCS) 2 or Pb(NO 3 ) 2 (0.162 and 0.166 g, respectively; 0.5 mmol) was placed in the main arm of a branched tube. EtOH or MeOH (15 mL) was carefully added to fill the arms. The tube was sealed and immersed in an oil bath at 60 • C while the branched arm was kept at ambient temperature. After about one week, X-ray suitable single crystals of the corresponding complex were formed in the cooler arm of the tube. Crystals were isolated by filtration.

Hirshfeld Surface Analysis
The molecular Hirshfeld surface [33][34][35] depends on the molecular electron distribution. By using Equation (1), the normalized contact distance (d norm ) is calculated by identifying both internal and Crystals 2020, 10, 568 4 of 15 external intermolecular contacts simultaneously [36]. d i and d e are the distances from the point to the nearest nucleus internal and external to the surface respectively. r i vdw and r e vdw are the internal and external van der Waals (vdW) radii. The 2D fingerprint plot  provides all intermolecular contacts that are involved in the crystal structures. The Hirshfeld surfaces were calculated by using the program CrystalExplorer [41]. (1)

Synthetic Considerations
The reaction of a suspension of either Pb(NCS) 2 or Pb(NO 3 ) 2 with L in a branched tube apparatus at 60 • C in MeOH yields dinuclear discrete complexes (1) and (2) in moderate to good yields, as represented in Scheme 1.

Structural Description
Complex (1) crystallizes in the triclinic space group P-1 with half of the dinuclear complex in the asymmetric unit, as represented in Figure 1. Each metal center is seven-coordinated by two pyridyl-imine units of the parent ligand L, one disordered terminal thiocyanate anion and two bridging N-coordinated thiocyanate anions. The S(1), C (30) and N(8) atoms of the terminal thiocyanate anion are disordered over two sets of sites with refined occupancies 0.880(7) and 0.120 (7). Each L exhibits a µ 4 -coordination mode towards Pb(II). The Pb-N Py distances are slightly longer than the Pb-N imine ones within the same pyridyl-imine fragment (see Table 2).

Hirshfeld Surface Analysis
The molecular Hirshfeld surface [33][34][35] depends on the molecular electron distribution. By using Equation (1), the normalized contact distance (dnorm) is calculated by identifying both internal and external intermolecular contacts simultaneously [36]. di and de are the distances from the point to the nearest nucleus internal and external to the surface respectively. ri vdw and re vdw are the internal and external van der Waals (vdW) radii. The 2D fingerprint plot  provides all intermolecular contacts that are involved in the crystal structures. The Hirshfeld surfaces were calculated by using the program CrystalExplorer [41].

Synthetic Considerations
The reaction of a suspension of either Pb(NCS)2 or Pb(NO3)2with L in a branched tube apparatus at 60 °C in MeOH yields dinuclear discrete complexes (1) and (2) in moderate to good yields, as represented in Scheme 1.

Structural Description
Complex (1) crystallizes in the triclinic space group P-1 with half of the dinuclear complex in the asymmetric unit, as represented in Figure 1. Each metal center is seven-coordinated by two pyridylimine units of the parent ligand L, one disordered terminal thiocyanate anion and two bridging Ncoordinated thiocyanate anions. The S(1), C (30) and N(8) atoms of the terminal thiocyanate anion are disordered over two sets of sites with refined occupancies 0.880(7) and 0.120 (7). Each L exhibits a μ 4coordination mode towards Pb(II). The Pb-NPy distances are slightly longer than the Pb-Nimine ones within the same pyridyl-imine fragment (see Table 2).

Figure 1.
View of the asymmetric unit of compound (1) with a partial atom numbering scheme. Hydrogen atoms are omitted for clarity. The unlabeled counterpart is generated through the symmetry operation. Thermal ellipsoids are drawn at the 30% probability level.  (1) with a partial atom numbering scheme. Hydrogen atoms are omitted for clarity. The unlabeled counterpart is generated through the symmetry operation. Thermal ellipsoids are drawn at the 30% probability level. Table 2. Selected (Å) and bond angles ( • ) for compounds (1) and (2) as determined by X-ray diffraction.

Complex-(1)
118. 16(8) Compound (1) exhibits C-H···N and C-H···S unconventional hydrogen-bonding contacts (see Table 3) and C-H···π interactions (see Table 4). The unconventional H-bonds involve (see Figure 2) the thiocianate group as H-bond acceptor and C-H donors belonging to the methyl or pyridine groups. The acidity of the H-atoms that participate in the H-bonding interactions is enhanced due to the coordination of the ligand (L) to the Pb(II) metal center, as further analyzed below. The C-H···π interactions are represented in Figure 3, where one carbon atom C(2) of the pyridine ring is in contact with the centroid of another pyridine ring (N6/C24-C28) at (1 + x, y, z) by leading the molecules to propagate along the [100] direction. Moreover, one methyl hydrogen atom (C23-H23) interacts with the centroid of the aryl ring (C16-C21) of the partner molecule at (−x, 2 − y, 1 − z). This interconnection of the parallel chains leads to the formation of a supramolecular assembly in the (101) plane as depicted in Figure 3. Table 3. Relevant hydrogen bonding parameters of compounds (1) and (2).

Y-X···Cg(I) X···Cg Y···Cg Y-X···Cg X-Perp Symmetry
Compound (1)  Table 3) and C-H•••π interactions (see Table 4). The unconventional H-bonds involve (see Figure 2) the thiocianate group as H-bond acceptor and C-H donors belonging to the methyl or pyridine groups. The acidity of the H-atoms that participate in the H-bonding interactions is enhanced due to the coordination of the ligand (L) to the Pb(II) metal center, as further analyzed below. The C-H•••π interactions are represented in Figure 3, where one carbon atom C(2) of the pyridine ring is in contact with the centroid of another pyridine ring (N6/C24-C28) at (1 + x, y, z) by leading the molecules to propagate along the [100] direction. Moreover, one methyl hydrogen atom (C23-H23) interacts with the centroid of the aryl ring (C16-C21) of the partner molecule at (−x, 2 − y, 1 − z). This interconnection of the parallel chains leads to the formation of a supramolecular assembly in the (101) plane as depicted in Figure 3.    (1) and (2).  Complex (2) crystallizes in the triclinic space group P-1 with half of the complex and one lattice MeOH molecule in the asymmetric unit ( Figure 4). Each metal center is nine-coordinated by two pyridyl-imine units of the parent ligand L, two types of bidentate nitrate anions (one terminal and one bridging ligand) and one monodentate nitrato bridging ligand. The ORTEP view of complex (2) is included in Figure 4 and, as noticed, the bond lengths and bond angles are in normal range ( Table 2) and are comparable with related structures reported earlier [2,9]. The carbon atoms (C11-C15) of one phenyl ring are disordered over two sets of sites and refined with half-occupancies. 2) and are comparable with related structures reported earlier [2,9]. The carbon atoms (C11-C15) of one phenyl ring are disordered over two sets of sites and refined with half-occupancies.  (Tables 3 and 4). In one substructure, the aryl ring carbon atom C21 interacts with the nitrate oxygen atom O4 at (-1 -x, -y, -z); therefore, forming a centrosymmetric dimeric ring centered at (1/2, 0, 0) (see Figure 5). These dimeric rings lead the molecules to propagate along the [010] direction. These parallel chains are further interconnected through the C7-H7B•••N3 hydrogen bonds by generating another centrosymmetric dimer centered at (0, ½, ½). The interconnection of these two centrosymmetric dimeric rings generates a supramolecular framework in the (011) plane (see Figure 5).   (2) with partial atom numbering scheme. Hydrogen atoms are omitted for clarity. The unlabeled counterpart is generated through the symmetry operation. Thermal ellipsoids are drawn at the 30% probability level.
In the solid-state, compound (2) is stabilized through weak C-H···O and C-H···N unconventional hydrogen bonds and C-H···π interactions (Tables 3 and 4). In one substructure, the aryl ring carbon atom C21 interacts with the nitrate oxygen atom O4 at (-1 -x, -y, -z); therefore, forming a centrosymmetric dimeric ring centered at (1/2, 0, 0) (see Figure 5). These dimeric rings lead the molecules to propagate along the [010] direction. These parallel chains are further interconnected through the C7-H7B···N3 hydrogen bonds by generating another centrosymmetric dimer centered at (0, 1 2 , 1 2 ). The interconnection of these two centrosymmetric dimeric rings generates a supramolecular framework in the (011) plane (see Figure 5). 2) and are comparable with related structures reported earlier [2,9]. The carbon atoms (C11-C15) of one phenyl ring are disordered over two sets of sites and refined with half-occupancies.  (Tables 3 and 4). In one substructure, the aryl ring carbon atom C21 interacts with the nitrate oxygen atom O4 at (-1 -x, -y, -z); therefore, forming a centrosymmetric dimeric ring centered at (1/2, 0, 0) (see Figure 5). These dimeric rings lead the molecules to propagate along the [010] direction. These parallel chains are further interconnected through the C7-H7B•••N3 hydrogen bonds by generating another centrosymmetric dimer centered at (0, ½, ½). The interconnection of these two centrosymmetric dimeric rings generates a supramolecular framework in the (011) plane (see Figure 5).  In another substructure, compound (2) generates a network in the (110) plane through weak C-H···O bonds where C3-H3 and C12-H12 groups acts as donors to the O2 and O1 atoms at (−1 + x, y, z) and (x, -1 + y, z), respectively ( Figure 6 and Table 3). The pyridine ring via the C28-H28 group acts as a donor to the centroid of another pyridine ring of the partner molecule at (1 + x, y, z) to build another network in (2) (see Figure 7 and Table 4). In another substructure, compound (2) generates a network in the (110) plane through weak C-H•••O bonds where C3-H3 and C12-H12 groups acts as donors to the O2 and O1 atoms at (−1 + x, y, z) and (x, -1 + y, z), respectively ( Figure 6 and Table 3). The pyridine ring via the C28-H28 group acts

Hirshfeld Surface
We have examined the Hirshfeld surfaces to quantify the contribution of noncovalent interactions in the crystal packing. In the present study, we have evaluated the contacts that are responsible in building the supramolecular assemblies. The symmetry-generated counterparts of the structures were not included in the Hirshfeld surface calculations. The Hirshfeld surface of In another substructure, compound (2) generates a network in the (110) plane through weak C-H•••O bonds where C3-H3 and C12-H12 groups acts as donors to the O2 and O1 atoms at (−1 + x, y, z) and (x, -1 + y, z), respectively ( Figure 6 and Table 3). The pyridine ring via the C28-H28 group acts as a donor to the centroid of another pyridine ring of the partner molecule at (1 + x, y, z) to build another network in (2) (see Figure 7 and Table 4).

Hirshfeld Surface
We have examined the Hirshfeld surfaces to quantify the contribution of noncovalent interactions in the crystal packing. In the present study, we have evaluated the contacts that are responsible in building the supramolecular assemblies. The symmetry-generated counterparts of the structures were not included in the Hirshfeld surface calculations. The Hirshfeld surface of

Hirshfeld Surface
We have examined the Hirshfeld surfaces to quantify the contribution of noncovalent interactions in the crystal packing. In the present study, we have evaluated the contacts that are responsible in Crystals 2020, 10, 568 9 of 15 building the supramolecular assemblies. The symmetry-generated counterparts of the structures were not included in the Hirshfeld surface calculations. The Hirshfeld surface of compounds (1) and (2) are mapped over d norm in Figure 8 (in the ranges (−0.3775 to 1.6794 Å) in (1) and (−0.5624 to 1.3287 Å) in (2)) and fragment patches (0.000 to 25.000 Å in (1) and 0.000 to 29.000 Å in (2), respectively). The d norm surfaces (Figure 8a,b) have been plotted based on the normalized function d i and d e using a white, red and blue color scheme. The circular deep red spots that are noticeable on the d norm surface of both compounds are due to the coordination bonds, since the symmetrically generated counterparts (see Figures 1 and 4) have not been included in the calculation. The nearest neighbor coordination environment of the molecules is identified from the color patches on the Hirshfeld surface based on their closeness to adjacent molecules. Therefore, the fragment patches show the appropriate approach for the identification of the nearest neighboring coordination environment of compounds (1) and (2) (see Figure 8c,d).
Crystals 2020, 10, x FOR PEER REVIEW 9 of 15 compounds (1) and (2) are mapped over dnorm in Figure 8 (in the ranges (-0.3775 to 1.6794 Å) in (1) and (-0.5624 to 1.3287 Å) in (2)) and fragment patches (0.000 to 25.000 Å in (1) and 0.000 to 29.000 Å in (2), respectively). The dnorm surfaces (Figure 8a,b) have been plotted based on the normalized function di and de using a white, red and blue color scheme. The circular deep red spots that are noticeable on the dnorm surface of both compounds are due to the coordination bonds, since the symmetrically generated counterparts (see Figures 1 and 4) have not been included in the calculation. The nearest neighbor coordination environment of the molecules is identified from the color patches on the Hirshfeld surface based on their closeness to adjacent molecules. Therefore, the fragment patches show the appropriate approach for the identification of the nearest neighboring coordination environment of compounds (1) and (2) (see Figure 8c,d).  The scattered points of the fingerprint plots (Figures 9 and 10) evidence all interactions involved within the structures. The long coordination bonds (Pb···N/N···Pb) and (Pb···O/O···Pb) are characterized in the fingerprint plots of (1) and (2), respectively. In (2), the (Pb···O/O···Pb) contacts contributed 1.7% to the total surface area of (2), whereas compound (1) contributed 1.9% due to (Pb···N/N···Pb) interaction (See Figures 9 and 10). In (2), (O···H/H···O) interaction comprises 28.5%, whereas compound (1) contributed 17.8% (S···H/H···S) interactions. The N···H/H···N interactions for both compounds are verified by two distinct spikes on the fingerprint plot (see Figures 9 and 10). The contribution of C···H/H···C contacts is higher in compound (1) compared to compound (2), and for both structures the C···H contact contributed more than its H···C counterpart. Moreover, the wings on the fingerprint plot of both structures designate the presence of C-H···π interaction. The total C···H/H···C contacts comprise 29.2% and 22.1% in compounds (1) and (2), respectively. All other contacts that are involved within the structures of the title compounds are quantified accordingly and are included in Figures 9 and 10. Crystals 2020, 10, x FOR PEER REVIEW 10 of 15

Mep Surface Analysis
In order to rationalize the noncovalent interactions described above in the crystal packing of compounds (1) and (2), the molecular electrostatic potential (MEP) surfaces have been computed for both compounds using the asymmetric unit. The MEP surface of compound (1) is shown in Figure 11, and it shows that the most negative MEP is located at the negative belt around the S-atom of the N-coordinated thiocyanate ligand (see Figure 11a). The MEP at the extension of the C=S bond is significantly smaller (in absolute value) than that at the belt. The MEP value at the N-atom of the S-coordinated thiocyanate ligand is slightly smaller (-52 kcal/mol). The most positive MEP value is located at the aromatic H-atoms of the Pb(II)-coordinated pyridine ring (+35 kcal/mol) due to inductive effects. The MEP value over the aromatic phenyl ring is slightly negative (-4 kcal/mol). The MEP values are also positive at the H-atoms of the methyl group and the phenyl rings. The formation of dinuclear centrosymmetric dimers, as observed in the X-ray structure, is favored electrostatically since the MEP value at the Pb(II) atom is positive (+10 kcal/mol) and negative at the N-atom of the thiocyanate ligand (-49 kcal/mol). In addition, the formation of the supramolecular H-bonded self-assembled dimers in (1)

Mep Surface Analysis
In order to rationalize the noncovalent interactions described above in the crystal packing of compounds (1) and (2), the molecular electrostatic potential (MEP) surfaces have been computed for both compounds using the asymmetric unit. The MEP surface of compound (1) is shown in Figure  11, and it shows that the most negative MEP is located at the negative belt around the S-atom of the N-coordinated thiocyanate ligand (see Figure 11a). The MEP at the extension of the C=S bond is significantly smaller (in absolute value) than that at the belt. The MEP value at the N-atom of the Scoordinated thiocyanate ligand is slightly smaller (-52 kcal/mol). The most positive MEP value is located at the aromatic H-atoms of the Pb(II)-coordinated pyridine ring (+35 kcal/mol) due to inductive effects. The MEP value over the aromatic phenyl ring is slightly negative (-4 kcal/mol). The MEP values are also positive at the H-atoms of the methyl group and the phenyl rings. The formation of dinuclear centrosymmetric dimers, as observed in the X-ray structure, is favored electrostatically since the MEP value at the Pb(II) atom is positive (+10 kcal/mol) and negative at the N-atom of the thiocyanate ligand (-49 kcal/mol). In addition, the formation of the supramolecular H-bonded selfassembled dimers in (1)   The MEP surface of compound (2) is shown in Figure 12, showing that the most negative MEP is located at the equatorial nitrato ligand (-60 kcal/mol). The MEP at the O-atom of the axial nitrato ligand is slightly smaller in absolute value (-55 kcal/mol). Similarly to compound (1), the most positive MEP value is located at the aromatic H-atoms of the Pb(II)-coordinated pyridine ring (+32 kcal/mol), due to the enhancement of their acidity upon complexation. The MEP value over the aromatic phenyl ring is slightly negative (-1 kcal/mol), and positive over the coordinated pyridine ligand (+8 kcal/mol). The MEP values are also positive at the H-atoms of the methyl group (+23 kcal/mol) and the phenyl rings (+21 kcal/mol). The formation of the dinuclear centrosymmetric dimer, as observed in the X-ray structure, is more favored electrostatically than that in (1) since the MEP value at the Pb(II) atom is more positive (+22 kcal/mol), and at the O-atom of the nitrato ligand (-49 kcal/mol) more negative than those of compound (1) (see Figure 11). Moreover, the formation of the two-dimensional network in compound (2) generated through C-H•••O hydrogen bonds in the (011) plane (see Figure 5) also agrees well with the MEP surface of (2), since the H-bond acceptor is the The MEP surface of compound (2) is shown in Figure 12, showing that the most negative MEP is located at the equatorial nitrato ligand (−60 kcal/mol). The MEP at the O-atom of the axial nitrato ligand is slightly smaller in absolute value (−55 kcal/mol). Similarly to compound (1), the most positive MEP value is located at the aromatic H-atoms of the Pb(II)-coordinated pyridine ring (+32 kcal/mol), due to the enhancement of their acidity upon complexation. The MEP value over the aromatic phenyl ring is slightly negative (−1 kcal/mol), and positive over the coordinated pyridine ligand (+8 kcal/mol).
The MEP values are also positive at the H-atoms of the methyl group (+23 kcal/mol) and the phenyl rings (+21 kcal/mol). The formation of the dinuclear centrosymmetric dimer, as observed in the X-ray structure, is more favored electrostatically than that in (1) since the MEP value at the Pb(II) atom is more positive (+22 kcal/mol), and at the O-atom of the nitrato ligand (−49 kcal/mol) more negative than those of compound (1) (see Figure 11). Moreover, the formation of the two-dimensional network in compound (2) generated through C-H···O hydrogen bonds in the (011) plane (see Figure 5) also agrees well with the MEP surface of (2), since the H-bond acceptor is the most negative O-atom. The C-H···N bonds that are also formed in the 2D layer are expected to be weaker, since the MEP value at the non-coordinated N-atom of the ligand is only −5 kcal/mol (see Figure 11a). This is also in good agreement with the Hirshfeld surface analysis of (2), since the quantification of the contribution of the O···H/H···O contacts is 28.5% and the contribution of the N-H/H-N contacts is only 7.4%.
Crystals 2020, 10, x FOR PEER REVIEW 12 of 15 most negative O-atom. The C-H•••N bonds that are also formed in the 2D layer are expected to be weaker, since the MEP value at the non-coordinated N-atom of the ligand is only -5 kcal/mol (see Figure 11a). This is also in good agreement with the Hirshfeld surface analysis of (2)

Concluding Remarks
The protocol to synthesize two new dinuclear Pb(II) coordination compounds involving 1,2diphenyl-1,2-bis((methyl(pyridin-2-yl)methylene)hydrazono)ethane ligand and SCN − and NO3 − counter anions is reported in this manuscript. Both complexes were characterized in the solid state by X-ray diffraction. The crystal packing of both compounds is dominated by C-H•••O,N,S noncovalent interactions, which is further evidenced by the Hirshfeld surface analysis and rationalized using the MEP surface analysis. The latter demonstrates that the most electron rich regions of the complexes that correspond to the anionic coligands are the most electron poor to the aromatic H-atoms, thus favoring the C-H•••O,N,S H-bonds. Moreover, although the ligand presents an extended aromatic surface (composed by four aromatic rings) π-π interactions are not observed. Interestingly, C-H•••π interactions seem to dominate the crystal packing in both compounds (1) and (2).
Author Contributions: Conceptualization, AF and G.M.; methodology, F.I.Z.; software, A.F. and S.K.S.; investigation, all authors; writing-original draft preparation, A.B., A.F. and S.K.S., writing-review and editing, all authors; visualization, A.F. and S.K.S.; project administration, A.F. and F.I.Z.; funding acquisition, A.F. and F.I.Z. All authors have read and agreed to the published version of the manuscript.

Funding:
The publication has been prepared with the support of the "RUDN University Program 5-100" (recipient F. I. Zubkov, synthesis of the ligands). This research was funded by the MICIU/AEI of Spain (project CTQ2017-85821-R FEDER funds).

Concluding Remarks
The protocol to synthesize two new dinuclear Pb(II) coordination compounds involving 1,2-diphenyl-1,2-bis((methyl(pyridin-2-yl)methylene)hydrazono)ethane ligand and SCN − and NO 3 − counter anions is reported in this manuscript. Both complexes were characterized in the solid state by X-ray diffraction. The crystal packing of both compounds is dominated by C-H···O,N,S noncovalent interactions, which is further evidenced by the Hirshfeld surface analysis and rationalized using the MEP surface analysis. The latter demonstrates that the most electron rich regions of the complexes that correspond to the anionic coligands are the most electron poor to the aromatic H-atoms, thus favoring the C-H···O,N,S H-bonds. Moreover, although the ligand presents an extended aromatic surface (composed by four aromatic rings) π-π interactions are not observed. Interestingly, C-H···π interactions seem to dominate the crystal packing in both compounds (1)  Funding: The publication has been prepared with the support of the "RUDN University Program 5-100" (recipient F. I. Zubkov, synthesis of the ligands). This research was funded by the MICIU/AEI of Spain (project CTQ2017-85821-R FEDER funds).