Crystal structures of trans-diaqua(3-R-1,3,5,8,12-pentaazacyclotetradecane)copper(II) isophthalate hydrates (R = benzyl or pyridin-3-ylmethyl)

The complex cations of the title compounds, (I) and (II), contain tetragonally distorted CuN4O2 octahedra with four N atoms of the azamacrocyclic ligand in the equatorial planes and two O atoms of the water molecules in the axial positions. In the crystals, the isophthalate counter-ions form layers as a result of O—H⋯O hydrogen bonds with the water molecules, which are pillared with the macrocyclic cations and lie parallel to the (01) and (100) planes in (I) and (II), respectively.

Though the isophthalate (1,3-benzenedicarboxylate) dianion is often used as bridging ligand in the construction of MOFs, a very limited number of its compounds with azamacrocyclic cations have been described to date and all they are complexes of the Ni II ion.

Structural commentary
Each Cu II ion in the complex cations in the title compounds (I) and (II) is coordinated in the equatorial plane by four secondary amine N atoms of the azamacrocyclic ligand in a square-planar fashion, and by two O atoms from the water molecules in the axial positions, resulting in a tetragonally distorted octahedral geometry (Table 1, Fig. 1 and Fig. 2).
The average equatorial Cu-N bond lengths are significantly shorter than the average axial Cu-O bond lengths [2.020 (9) versus 2.495 (12) Å for (I) and 2.015 (4) versus 2.507 (7) Å for (II)], which can be attributed to a large Jahn-Teller distortion. The Cu II ions are displaced from the nearly planar (r.m.s. deviations less than 0.01 Å ) mean planes of the N 4 donor atoms towards the O1W water molecule by 0.024 and 0.033 Å in (I) and (II), respectively. Both coordinated macrocyclic ligands adopt the most energetically favourable trans-III (R,R,S,S) conformation (Bosnich et al., 1965) with the five-membered chelate rings in gauche [bite angles 86.28 (1) for (I) and 86.30 (7) for (II)] and six-membered chelate rings in chair [bite angles 93.7 (2) for (I) and 93.7 (9) for (II)] conformations. The methylene group of the substituent at the non-coordinated nitrogen atoms N3 in the six-membered chelate rings is axially oriented and the sum of the C-N-C angles around these atoms [345.6 and 348.1 for (I) and (II), respectively] indicates their partial sp 2 character (Tsymbal et al., 2019).
The isophthalate dianions in the title compounds counterbalance the charge of the complex cations. One carboxylic group of the isophthalate (O1/O2/C) is nearly coplanar with the mean plane of the aromatic fragment [dihedral angles being 2.4 (3) and 3.6 (4) in (I) and (II), respectively], while the second (O3/O4/C) is tilted by 11.6 (3) and 21.1 (4) in (I) and (II), respectively. The C-O bond lengths in the carboxylic groups are nearly equal, thus indicating essential electron delocalization.
Among the water molecules of crystallization, O3W in (I) is fully occupied, while that in (II) has a site occupancy of 50%.

Figure 2
View of the asymmetric unit of (II), showing the atom-labelling scheme, with displacement ellipsoids drawn at the 30% probability level. H atoms attached to carbon atoms have been omitted for clarity.

Figure 1
View of the asymmetric unit of (I), showing the atom-labelling scheme, with displacement ellipsoids drawn at the 30% probability level. H atoms attached to carbon atoms have been omitted for clarity.
Additionally, two positions for disordered water molecules (O4W and O5W), each with 20% population, were found in (II). Because of their low partial population, these were not considered further in the analysis of the hydrogen-bonding network.

Figure 4
Nearest surrounding of the macrocyclic cation in (II) formed by hydrogen bonding (dashed lines). [Symmetry codes: (i) x + 1, y, z; (ii) x + 1, Ày between the methylene and methine groups of the macrocyclic ligand and oxygen atoms of carboxylic groups, the water molecule O3W and atom N6 of the substituent in the neighbouring macrocycle (Table 3). As can be seen from Figs. 3 and 4, because of the hydrogen bonding, two pairs of isophthalate anions are situated above and below the imaginary plane of the macrocyclic ligand. Each pair is further bound with symmetry-related partners via hydrogen bonding with the water molecule of crystallization, O3W, thus forming layers of anions lying parallel to the (101) and (100) planes in (I) and (II), respectively (Figs. 5 and 6), which thus are pillared with macrocyclic cations.

Database survey
A search of the Cambridge Structural Database (CSD, version 5.39, last update August 2018; Groom et al., 2016) indicated that only three Cu II -perchlorate complexes of azacyclam macrocycles bearing N-alkyl groups decorated with aromatic rings have been reported (Tsymbal et al., 2010). In addition, four related dicopper(II) complexes with a p-xylylene-bridged bis(azacyclam) ligand and terephthalate anion have been described, none of which includes the diaqua Cu II azacyclam cation . At the same time, four complexes containing macrocyclic cations and an isophthalate dianion have been reported, all of them being formed by an Ni II ion coordinated to a C-methyl-substituted cyclam. Thus, the title compounds (I) and (II) are the first examples of diaqua Cu II azacyclam cations described so far.

Synthesis and crystallization
All chemicals and solvents used in this work were purchased from Sigma-Aldrich and used without further purification. The starting complexes, [Cu(L1)](ClO 4 ) 2 and [Cu(L2)](ClO 4 ) 2 , were prepared by a method reported in the literature (Tsymbal et al., 2010) using benzylamine or 3-picolylamine, respectively, as locking reagents.
Safety note: perchlorate salts of metal complexes are potentially explosive and should be handled with care.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 4 Sheets of isophthalate dianions parallel to the (101) plane in (I).
Macrocyclic ligands and H atoms at carbon atoms of the carboxylate anions are omitted, only water molecules coordinated to Cu II (balls) participating in the formation of a carboxylate layer are shown (O1Wgreen, O2W -dark blue, O3W -violet). Hydrogen bonds are shown as dashed lines.

Figure 6
Sheets of isophthalate dianions parallel to the (100) plane in (II). Macrocyclic ligands and H atoms at carbon atoms of the carboxylate anions are omitted, only water molecules coordinated to Cu II (balls) participating in the formation of a carboxylate layer are shown (O1Wgreen, O2W -dark blue, O3W -violet). Hydrogen bonds are shown as dashed lines.

Computing details
For both structures, data collection: APEX2 (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT (Bruker, 2007); program(s) used to solve structure: SHELXS2014 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015b); molecular graphics: Mercury (Macrae et al., 2008); software used to prepare material for publication: publCIF (Westrip, 2010). 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (