Inﬂuence of the Substituted Ethylenediamine Ligand on the Structure and Properties of [Cu(diamine) 2 Zn(NCS) 4 ] · Solv. Compounds

: In this paper, three new heterometallic compounds were described and compared with the molecular formula [Cu(pn) 2 Zn(NCS) 4 ] ( 1 ), [Cu( N , N -Me 2 -en) 2 Zn(NCS) 4 ] ( 2 ), [Cu( N -Me-en) 2 Zn(NCS) 4 ] · 12 H 2 O ( 3 ) where pn = 1,2 − diaminopropane, N , N -Me 2 -en = N , N -dimethylethylenediamine and N -Me-en = N -methylethylenediamine, respectively. The compounds mentioned above were characterized by elemental analysis, infrared (IR), electronic, electron paramagnetic resonance (EPR) spectra, and magnetic studies. Crystal structures for 1 and 2 were determined by X-ray analysis. Copper(II) in these complexes adopts 4 + 2 coordination with two elongated (in 2 very long and considered as semi-coordination) Cu-S bonds. The Cu-N and Cu-S bond lengths depend on substituent position affecting steric hindrance and hence a topology of the chain. Both chains form different zigzag patterns characterized by one or two Cu-Zn distance values. Weak magnetic interaction is observed, ferromagnetic in the case of 1 and antiferromagnetic in the case of 2 , due to diversity of the above structural features. 1,2-diaminopropane reﬁnement 0.6:0.4 reﬁned ﬁnal


Introduction
In recent decades, coordination polymers (CPs) have engaged attention owing to their interesting structural topology features and resulting properties. The key towards the diversity of CPs is the design of underlying topology and directionality, which is realized by a judicious choice of metal centers and ligands. The thiocyanato ligands are often considered because of their ambidentate nature [1-4] and ability to efficiently mediate super-exchange magnetic interaction between paramagnetic metal centers [5]. The thiocyanato-N/S-metalates in reaction with various cationic tectons form numerous zero- [6,7], one- [8,9], two- [10,11], and three-dimensional [4,12] thiocyanato bridged compounds, which manifest interesting structural, physicochemical properties, as well as sometimes potential applications.

Physical Measurements
Elemental analysis was performed on a Vario Macro CHN Analyzer (Elementar Analysensysteme GmbH, Langenselbold, Germany). Water content was determined on an SDT 2600 (TA Instruments, New Castle, USA) by simultaneous thermogravimetric analysis (TGA) and differential thermal analysis (DTA) in air atmosphere. Infrared spectra (IR) were recorded on a Vertex 70 v Spectrometer (Bruker Optik GmbH, Ettlingen, Germany) in the range 4000-100 cm -1 . Reflectance spectra were recorded in MgO on the SPECORD M40 Spectrophotometer (Carl Zeiss, Jena, DDR) in the range 30,000-12,000 cm -1 . Electron Paramagnetic Resonance (EPR) spectra of powdered samples were recorded at room temperature with an EPR SE/X 2541 M spectrometer (Radiopan, Poznań, Poland) in X band (ca. 9.33 GHz) with 100 kHz modulation. The microwave frequency was monitored with a frequency meter. The magnetic field was measured with an automatic NMR-type magnetometer. Magnetic measurements in the temperature range 1.8-300 K were performed using a SQUID MPMS-3 magnetometer (Quantum Design, San Diego, USA) at the magnetic field of 0.1 T. The data were corrected for the sample holder, diamagnetism using the Pascal's constants [23] (-278 and -302·10 -6 cm 3 mol -1 , for compounds 1 and 2, respectively) and temperature independent paramagnetism [24]. The effective magnetic moment was calculated from the equation: µ eff = 2.828 (χ M corr · T) 1/2 . Magnetization versus magnetic field measurements were carried out at 1.8 K in the magnetic field range 0-7 Tesla.

Structural Analysis
Diffraction data were collected at BL14.2 beamline (HZB, Berlin, BESSY II synchrotron) at 100 K for [Cu(pn) 2 ][Zn(NCS) 4 ] (1) and on Oxford Sapphire with CCD area detector [25] at room temperature for [Cu(N,N-Me 2 en) 2 Zn(NCS) 4 ] (2). The data were processed using XDS for 1 and CrysAlis for 2. Subsequently, these data were reprocessed with CrysAlis to apply the numerical absorption correction (RED171 package of programs, Oxford Diffraction, 2000 [25]). Both structures were solved by direct methods and refined by full-matrix least-squares techniques on F 2 with a SHELXL program [26] with anisotropic thermal displacement parameters for all heavy atoms. Positions of hydrogen atoms attached to carbon atoms were assigned at calculated positions, whereas positions of hydrogen atoms attached to nitrogen atoms were found from difference electron density maps. All hydrogen atoms were refined with isotropic thermal displacement parameters fixed to a value of 20% or 50% higher than those of the corresponding C or N atoms. In 1, we found two sets for positionally disordered CH 2 and CH groups from 1,2-diaminopropane ligands. The refinement showed that they are populated 0.6:0.4 and 0.7:0.3 for Cu2 and Cu3 moieties, respectively. In 2, positional disorder for CH 2 and CH 3 groups is also observed with two sets refined with final occupancies 0.62 and 0. 38. In 2, two geometrical restraints (DFIX) were applied for C5-H5C/D bonds. Additionally, an extinction coefficient was also refined showing value of 0.0264. All figures were prepared in DIAMOND [27] and ORTEP-3 [28,29]. The details concerning the data collection and refinement processes of the compound reported in this paper are presented in Table 1.
CCDC 1946058 and 1946055 contain the supplementary crystallographic data for 1 and 2, respectively. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre [30].

General Characterization
Compounds 1 and 2 were synthesized by mixing stochiometric amounts of in situ prepared aqueous solutions of the appropriate bis(diamine)copper(II) congeners and tetra(thiocyanato-N)zincate(II) complexes. Elemental analyses confirmed the composition of the complexes investigated. All obtained compounds are air stable, water soluble, and could be easily recrystallized giving violet or dark violet crystals.

. Infrared Spectra
The infrared spectra of 1 and 2 are quite similar to each other and to that of [Cu(en) 2 Zn(NCS) 4 ]·H 2 O [19]. They show the characteristic absorptions due to thiocyanato ligands as follows: an intense bands at 2085, 2047 (1), 2133sh, 2097 cm −1 (2), a medium band at 831 (1), 820 cm −1 (2), and strong band at 477 (1), 472 cm −1 (2) due to vibrations of the CN, CS, and deformation of NCS groups, respectively [13,14,40]. The broad and split band in the region 2150-2000 cm −1 corresponds to the presence of bridging and N-bonded thiocyanate groups. As pointed out in the literature, the shoulder at the higher frequency (ca. and above 2100 cm −1 ) can be assigned to bridging ions [40]. The expected low intensity new ν CS bands are masked by strong and medium bands from rocking NH 2

Structure of Compound (1)
Compound 1 crystallizes in the triclinic P -1 space group. In the asymmetric unit of the unit cell, a zinc block with four thiocyanate anions and two halves of copper units was found with only one symmetrically independent molecule of pn in the coordination sphere of each copper ions ( Figure 1). In this structure, both copper atoms are positioned at the inversion centers. CH 2 and CH groups in both copper units reveal positional disorder with two populations: 0.6:0.4 and 0.7:0.3 for Cu2 and Cu3, respectively, which is related to both enantiomers of chiral pn ligand (S and R, respectively) coordinated to both copper(II) ions from the asymmetric unit cell. The selected bond distances and angles are listed in Table 2 and Table S1. Both copper coordination spheres are composed of four nitrogen atoms from two pn molecules and two sulfur atoms from two thiocyanate anions. Both copper(II) ion adopt 4 + 2 coordination with four short Cu−N bonds ranging from 1.993(2) to 2.031(3) Å for Cu2 and from 2.006(3) to 2.017(3) Å for Cu3. Hence, only in the Cu2 block, we observe asymmetry in Cu-N bonds: NH 2 group next to the CH group shows significant shortening of the Cu−N bond. The N−Cu−N angles show values of 84.92(10) and 84.73(13) • inside Cu2 and Cu3 chelate rings, respectively, 95.08(10) and 95.27(13) • for atoms belonging to two different organic ligands and 180.0 • for trans oriented nitrogen atoms. Both crystallographically independent [Cu(pn) 2 ] 2+ moieties are inclined by 30.94(17) • . The coordination sphere is completed by two sulfur atoms from thiocyanato ligands occupying trans positions and found at long distances but significantly differing: 2.9718(8) and 3.0432(9) Å for S3 and S4 atoms, respectively. They form S−Cu−N angles ranging from 85.47(8) to 94.53(8) • and from 88.00(8) to 92.00(8) • for S3 and S4 atoms, respectively. Zinc(II) ion was found in a tetrahedral environment with four nitrogen atoms from thiocyanate anions forming the coordination sphere. Zn−N bonds are slightly shorter for non-bridging nitrogen atoms (1.950(3) and 1.965(3) Å), whereas, for both bridging nitrogen atoms, we found 1.969(3) Å. The N−Zn−N angles range from 103.74(13) to 114.19(12) • for angles between bridging and terminal thiocyanato ligands. The angles between the non-bridging ligands (111.90(12) • ) as well as between the bridging ligands (105. 56(15) • ) fall into this broad range. Generally, the Zn(NCS) 4 2− unit has geometrical parameters consistent with those normally observed [43]. The detailed analysis of Cu(II) and Zn(II) coordination spheres for 1, 2, and comparison with Cu(en) 2    In the packing, we observe infinite chains running along the [1 0 −1] direction with alternately arranged copper and zinc ions showing the following repeating motif: …ZnCu2ZnCu3…( Figures  2,3). Copper atoms form the axis of the zigzag, whereas zinc(II) cations were found above and below the axis of the chain propagation. Due to the presence of two crystallographically distinct blocks, there is a variety of intermetallic distances. In the chain, Zn1−Cu3 separation is small (5.0391(5) Å), whereas Zn1−Cu2 distance is much longer (6.3630(6) Å). Hence, Zn−Zn distance across Cu2 atom is 12.726 and across Cu3 atom 10.078 Å. These differences are due to the Zn−S−Cu angle, which, for S3 thiocyanato bridging, Cu2 and Zn1 atoms are much bigger (108.77(2)°) than for S4 anion coupling Cu3 and Zn1 atoms (77.83(2)°). It results in an "irregular" zigzag with one side significantly It should be noted that a term "irregular" means that two values describe adjacent Cu-Zn distances, whereas "regular" corresponds to only one such value (compare Figures 2,5), which is related to the number of independent copper moieties in the asymmetric units. In 1, the shortest intermetallic distances between paramagnetic copper(II) ions are 7.569, 8.481, and 8.663 Å. The second value corresponds to intrachain separation, whereas other In the packing, we observe infinite chains running along the [1 0 −1] direction with alternately arranged copper and zinc ions showing the following repeating motif: . . . ZnCu2ZnCu3 . . . (Figures 2  and 3). Copper atoms form the axis of the zigzag, whereas zinc(II) cations were found above and below the axis of the chain propagation. Due to the presence of two crystallographically distinct blocks, there is a variety of intermetallic distances. In the chain, Zn1−Cu3 separation is small (5.0391(5) Å), whereas Zn1−Cu2 distance is much longer (6.3630(6) Å). Hence, Zn−Zn distance across Cu2 atom is 12.726 and across Cu3 atom 10.078 Å. These differences are due to the Zn−S−Cu angle, which, for S3 thiocyanato bridging, Cu2 and Zn1 atoms are much bigger (108.77(2) • ) than for S4 anion coupling Cu3 and Zn1 atoms (77.83(2) • ). It results in an "irregular" zigzag with one side significantly extended (Zn1−Cu2−Zn1[1−x, 1−y, 1−z]). It should be noted that a term "irregular" means that two values describe adjacent Cu-Zn distances, whereas "regular" corresponds to only one such value (compare Figure 2 with Figure 5), which is related to the number of independent copper moieties in the asymmetric units. In 1, the shortest intermetallic distances between paramagnetic copper(II) ions are 7.569, 8.481, and 8.663 Å. The second value corresponds to intrachain separation, whereas other distances describe separations between copper(II) ions in adjacent chains translated along a and c axes, respectively. The crystal structure is maintained by N−H . . . N and N−H . . . S hydrogen bonds ( Table 3). The former interactions are observed for N21−H21 from the pn molecule and N1 as well as N4 atoms from thiocyanate anions and result in a shorter Cu3−Zn1 distance and more compact structure of this part of the chain. There were not detected any similar interactions between N11 ligand and thiocyanate anion, and, consequently, that part of the zigzag exposes a more extended structure. N-H . . . S hydrogen bonds mediate interactions between adjacent chains forming a robust network of hydrogen bonds. They involve rather non-bridging sulfur atoms, and the N21−H21a . . . S3[1−x, 1−y, 2−z] bond is the only exception. This hydrogen bonds pattern is due to significant differences in thiocyanate geometry with adjacent metal ions. The detailed analysis of Zn-N-C angles can be found in Supplementary Materials. N4 atoms from thiocyanate anions and result in a shorter Cu3−Zn1 distance and more compact structure of this part of the chain. There were not detected any similar interactions between N11 ligand and thiocyanate anion, and, consequently, that part of the zigzag exposes a more extended structure. N-H…S hydrogen bonds mediate interactions between adjacent chains forming a robust network of hydrogen bonds. They involve rather non-bridging sulfur atoms, and the N21−H21a…S3[1−x, 1−y, 2−z] bond is the only exception. This hydrogen bonds pattern is due to significant differences in thiocyanate geometry with adjacent metal ions. The detailed analysis of Zn-N-C angles can be found in Supplementary Materials.    N4 atoms from thiocyanate anions and result in a shorter Cu3−Zn1 distance and more compact structure of this part of the chain. There were not detected any similar interactions between N11 ligand and thiocyanate anion, and, consequently, that part of the zigzag exposes a more extended structure. N-H…S hydrogen bonds mediate interactions between adjacent chains forming a robust network of hydrogen bonds. They involve rather non-bridging sulfur atoms, and the N21−H21a…S3[1−x, 1−y, 2−z] bond is the only exception. This hydrogen bonds pattern is due to significant differences in thiocyanate geometry with adjacent metal ions. The detailed analysis of Zn-N-C angles can be found in Supplementary Materials.     Compound 2 crystallizes in the monoclinic centrosymmetric P 2 1 /m space group with copper positioned at the inversion center and zinc and two (S1 and S2) thiocyanates located at the m plane. In the asymmetric unit of the unit cell, a copper unit was found with only one symmetrically independent N,N-Me 2 -en molecule and a zinc block with three thiocyanate anions ( Figure 4). In this structure, N,N-Me 2 -en reveals a positional disorder for CH 2 and CH 3 groups with two populations: 0.62:0. 38. The selected bond distances and angles are listed in Table 4 and Table S2. Both copper coordination spheres are composed of four nitrogen atoms from two N,N-Me 2 -en molecules and two sulfur atoms from two thiocyanate anions. Hence, copper(II) ion adopt 4 + 2 coordination with four short Cu−N bonds ranging from 1.980(2) to 2.085(2) Å and two sulfur atoms from thiocyanate anions found at very long identical distances 3.3477(14) Å that can be considered only as a semi-coordination. The N−Cu−N angles show following values 84.79(9) inside the Cu2 chelate ring, 95.21(9) • for atoms belonging to two different organic ligands, and 180.0 • for trans oriented nitrogen atoms. Sulfur atoms form S−Cu−N angles ranging from 86.86 (7) to 93.14(7) • . The zinc(II) ion was found in the tetrahedral environment with four nitrogen atoms from thiocyanate anions forming the coordination sphere. Zn−N bonds are slightly shorter for nitrogen atoms from bridging thiocyanates (1.950(3) Å), whereas, for nitrogen atoms from both non-bridging ligands, we found 1.955 (4) 4)  Compound 2 crystallizes in the monoclinic centrosymmetric P 21/m space group with copper positioned at the inversion center and zinc and two (S1 and S2) thiocyanates located at the m plane.

D-H A d(D-H) [Å] d(H•••A) [Å] d(D•••A) [Å] <DHA [°]
In the asymmetric unit of the unit cell, a copper unit was found with only one symmetrically independent N,N-Me2-en molecule and a zinc block with three thiocyanate anions ( Figure 4). In this structure, N,N-Me2-en reveals a positional disorder for CH2 and CH3 groups with two populations: 0.62:0. 38. The selected bond distances and angles are listed in Table 4 and Table S2. Both copper coordination spheres are composed of four nitrogen atoms from two N,N-Me2-en molecules and two sulfur atoms from two thiocyanate anions. Hence, copper(II) ion adopt 4 + 2 coordination with four short Cu−N bonds ranging from 1.980(2) to 2.085(2) Å and two sulfur atoms from thiocyanate anions found at very long identical distances 3.3477(14) Å that can be considered only as a semi-coordination. The N−Cu−N angles show following values 84.79(9) inside the Cu2 chelate ring, 95.21(9)° for atoms belonging to two different organic ligands, and 180.0° for trans oriented nitrogen atoms. Sulfur atoms form S−Cu−N angles ranging from 86.86(7) to 93.14(7)°. The zinc(II) ion was found in the tetrahedral environment with four nitrogen atoms from thiocyanate anions forming the coordination sphere. Zn−N bonds are slightly shorter for nitrogen atoms from bridging thiocyanates     In packing, we observe chains running along the b-axis showing a regular zigzag pattern with copper(II) ions indicating the axis of this zigzag and zinc(II) cations positioned above and below it ( Figures 5 and 6). There is one intermetallic value describing separation between copper and zinc ions in the chain being 6.879 Å, whereas distances between adjacent copper cations and adjacent zinc cations are much bigger, being 8.249 and 13.758 Å, respectively. The Cu2−S3−Zn1 angle is 116.31 • . The shortest distances between paramagnetic copper ions are 8.249 and 8.263 Å. The former corresponds to intrachain separation, and it is a half of the b-axis, whereas the latter describes a distance between copper(II) ions from two adjacent chains translated along the a-axis. The crystal network is maintained via few hydrogen bonds created by sulfur atoms (Table 5). An intrachain hydrogen bond was detected between H9A from the main population of the CH 3 group and a bridging S3 sulfur atom. Additionally, there are two N−H . . . S hydrogen bonds between adjacent chains. Hence, NH 2 group is crucial for crystal network formation. In packing, we observe chains running along the b-axis showing a regular zigzag pattern with copper(II) ions indicating the axis of this zigzag and zinc(II) cations positioned above and below it ( Figures 5,6). There is one intermetallic value describing separation between copper and zinc ions in the chain being 6.879 Å, whereas distances between adjacent copper cations and adjacent zinc cations are much bigger, being 8.249 and 13.758 Å, respectively. The Cu2−S3−Zn1 angle is 116. 31°. The shortest distances between paramagnetic copper ions are 8.249 and 8.263 Å. The former corresponds to intrachain separation, and it is a half of the b-axis, whereas the latter describes a distance between copper(II) ions from two adjacent chains translated along the a-axis. The crystal network is maintained via few hydrogen bonds created by sulfur atoms (Table 5). An intrachain hydrogen bond was detected between H9A from the main population of the CH3 group and a bridging S3 sulfur atom. Additionally, there are two N−H…S hydrogen bonds between adjacent chains. Hence, NH2 group is crucial for crystal network formation.    In packing, we observe chains running along the b-axis showing a regular zigzag pattern with copper(II) ions indicating the axis of this zigzag and zinc(II) cations positioned above and below it (Figures 5,6). There is one intermetallic value describing separation between copper and zinc ions in the chain being 6.879 Å, whereas distances between adjacent copper cations and adjacent zinc cations are much bigger, being 8.249 and 13.758 Å, respectively. The Cu2−S3−Zn1 angle is 116. 31°. The shortest distances between paramagnetic copper ions are 8.249 and 8.263 Å. The former corresponds to intrachain separation, and it is a half of the b-axis, whereas the latter describes a distance between copper(II) ions from two adjacent chains translated along the a-axis. The crystal network is maintained via few hydrogen bonds created by sulfur atoms (Table 5). An intrachain hydrogen bond was detected between H9A from the main population of the CH3 group and a bridging S3 sulfur atom. Additionally, there are two N−H…S hydrogen bonds between adjacent chains. Hence, NH2 group is crucial for crystal network formation.     The crystal structure of the compound 3 is unknown (see Experimental and Supplementary Materials).

EPR
The compounds 1 and 2 exhibit an axial type of EPR spectra. The room temperature EPR spectra are shown in Figure 7 (for 3, see Figure S1). This category of spectra is consistent with copper(II) complex of axial "effective symmetry" of ligand field in line with the pseudooctahedral environment [33]. The EPR spectra were simulated using the program SPIN written by Dr. Andrew Ozarowski from NHMFL, University of Florida, with the resonance field calculated by full diagonalization of an energy matrix. A large anisotropy of the line width had to be used in the simulation procedure in the case of 1. The line width for 2 is ca. 2.5 to 5 times smaller than that for 1 for perpendicular and parallel orientation, respectively (compare Figure 7b with Figure 7a). The simulated g-values, 2.190 (1) and 2.195 (2) for g || , and 2.054 (1) and 2.046 (2) for g ⊥ , respectively, correspond to d x 2 −y 2 ground state of copper(II) ion.
According to the perturbation theory, using only the first-order terms in the formulas for g || and g ⊥ , the G value defined as G = (g || − 2) / (g ⊥ − 2) for the d x 2 −y 2 ground state should be about 4 [33,46]. In our case, those values are 3.5−4.2. Hence, the observed crystal g values are valid and equal to the molecular g values describing the symmetry of single paramagnetic center, while the exchange coupling is small but not insignificant (see below) [46]. The crystal structure of the compound 3 is unknown (see Experimental and Supplementary Materials).

EPR
The compounds 1 and 2 exhibit an axial type of EPR spectra. The room temperature EPR spectra are shown in Figure 7 (for 3, see Figure S1). This category of spectra is consistent with copper(II) complex of axial "effective symmetry" of ligand field in line with the pseudooctahedral environment [33]. The EPR spectra were simulated using the program SPIN written by Dr. Andrew Ozarowski from NHMFL, University of Florida, with the resonance field calculated by full diagonalization of an energy matrix. A large anisotropy of the line width had to be used in the simulation procedure in the case of 1. The line width for 2 is ca. 2.5 to 5 times smaller than that for 1 for perpendicular and parallel orientation, respectively (compare Figure 7b with Figure 7a). The simulated g-values, 2.190 (1) and 2.195 (2) for g||, and 2.054 (1) and 2.046 (2) for g ⊥ , respectively, correspond to dx 2 -y 2 ground state of copper(II) ion. According to the perturbation theory, using only the first-order terms in the formulas for g|| and g ⊥ , the G value defined as G = (g|| − 2) / (g ⊥ − 2) for the dx 2 -y 2 ground state should be about 4 [33,46]. In our case, those values are 3.5−4.2. Hence, the observed crystal g values are valid and equal to the molecular g values describing the symmetry of single paramagnetic center, while the exchange coupling is small but not insignificant (see below) [46].

Modelling of Magnetic Interactions
The compounds 1 and 2 investigated in this work form an infinite chains of alternating paramagnetic copper(II) and diamagnetic zinc(II) ions connected by thiocyanato anions forming a pattern -SCN-Zn-NCS-Cu-. In such a case with paramagnetic centers separated by eight bonds and at least 8.2 Å, we can expect rather weak interactions. Despite this, in order to describe the magnetic properties, we can try to use a Heisenberg-Dirac-Van Vleck Hamiltonian (HDVV) (Equation (1)): where J is the exchange parameter, and S is the spin operator. The behavior of a coupled chain of quantum spins with S = ½ was calculated based on classical Fisher [48], and Boner and Fisher papers [49], and a polynomial approximation given by Hiller et al. [50] (Equation (2)): continue the Brillouin function (Figures 8,9; for 3, see Figure S2). Values of magnetizations of 1.02 and 1.05 B.M. at 7 T, for 1 and 2, respectively, confirm the presence of S = 1/2.

Modelling of Magnetic Interactions
The compounds 1 and 2 investigated in this work form an infinite chains of alternating paramagnetic copper(II) and diamagnetic zinc(II) ions connected by thiocyanato anions forming a pattern -SCN-Zn-NCS-Cu-. In such a case with paramagnetic centers separated by eight bonds and at least 8.2 Å, we can expect rather weak interactions. Despite this, in order to describe the magnetic properties, we can try to use a Heisenberg-Dirac-Van Vleck Hamiltonian (HDVV) (Equation (1)): where J is the exchange parameter, and S is the spin operator. The behavior of a coupled chain of quantum spins with S = ½ was calculated based on classical Fisher [48], and Boner and Fisher papers [49], and a polynomial approximation given by Hiller et al. [50] (Equation (2)):

Modelling of Magnetic Interactions
The compounds 1 and 2 investigated in this work form an infinite chains of alternating paramagnetic copper(II) and diamagnetic zinc(II) ions connected by thiocyanato anions forming a pattern -SCN-Zn-NCS-Cu-. In such a case with paramagnetic centers separated by eight bonds and at least 8.2 Å, we can expect rather weak interactions. Despite this, in order to describe the magnetic properties, we can try to use a Heisenberg-Dirac-Van Vleck Hamiltonian (HDVV) (Equation (1)): where J is the exchange parameter, and S is the spin operator. The behavior of a coupled chain of quantum spins with S = 1 2 was calculated based on classical Fisher [48], and Boner and Fisher papers [49], and a polynomial approximation given by Hiller et al. [50] (Equation (2)): where x = |J|/ kT and A = 0.25000, B = 0.18297, C = 1.5467, D = 3.4443 for S = 1 2 , and the other symbols have their usual meaning. Least-squares fitting of experimental data for 1 and 2 to Equation (2) gives the 2J, g, and R values collected in Table 6 (R is the factor defined as (Equation 3): Exchange interactions in 1 and 2 are undeniably very weak. The reasons are as follows. For the elongated octahedral copper(II) complex, the dx 2 −y 2 SOMO orbital is not directed to the bridging ligand. Nevertheless, it is very possible that some spin density also exists on the dz 2 orbital of copper(II) ion considering the deformation of coordination sphere from an "ideal" elongated octahedron. As a consequence of these, a very weak magnetic coupling was observed. A similar effect has been previously observed for some thiocyanato bridged compounds, although the bridging units were paramagnetic  The molecular field approximation was also applied as an alternation. It seems very rational remembering that the Cu···Cu distances within and between the chains are comparable ( Table 7). The hydrogen bonds (Tables 3 and 5) could also transmit magnetic interaction between paramagnetic centers [17,58]. The temperature dependencies of magnetic susceptibilities in the whole measured range for 1 and the above 10 K for 2 obey the Curie-Weiss law (Equation (4)): a Definition-see above p. 3.2.1; b Data were calculated on the basis of cif files; they were not given in the original paper [18].
The Weiss constant is defined as Equation (5): where J' is the molecular field exchange parameter, and z is the number of the nearest neighbors [59].
The best fitted values of the Curie (C) and Weiss constants (θ), and R factors defined as above are given in Table 6 along with calculated average g and zJ' values. The Curie constant implies the g values that are smaller than average values calculated from EPR spectra. Disagreement between the g values (EPR vs. magnetic susceptibility) are common.

Comparison of Structures
Structure 1 and Structure 2 copper(II) ions adopt 4 + 2 coordination sphere (distorted octahedron), and a distorted tetrahedral environment of Zn(II) ions occurs in both structures ( Table 7). The main difference concerns the topology of the chain in 1 and 2. For 1, the "irregular" run of the main chain can be observed, while the chain of the 2 shows the characteristic zigzag shape (Figure 10 (Table 7). The difference also relates to the localization of zinc ions according to chain direction determined by copper(II) ions. In 1, angles between the Cu2−Cu3 and Cu2−Zn1 as well as Cu3−Zn1 are 36.3 and 48.3 • , respectively, whereas, in 2, there is only one angle characterizing mutual positions of copper and zinc atoms, and it is much bigger being 53.2 • (Scheme 1).
relates to the localization of zinc ions according to chain direction determined by copper(II) ions. In 1, angles between the Cu2−Cu3 and Cu2−Zn1 as well as Cu3−Zn1 are 36.3 and 48.3°, respectively, whereas, in 2, there is only one angle characterizing mutual positions of copper and zinc atoms, and it is much bigger being 53.2° (Scheme 1). The shortest distances between paramagnetic copper ions are comparable in the both structures and show values as follows: 7.569, 8.481, 8.663 and 8.249, 8.263 Å for 1 and 2, respectively. The intermetallic value describing separation between copper and zinc ions in the chain of 2 is much longer (6.879 Å) than the Cu−Zn distances in 1 (5.0391(5) and 6.3630(6) Å) ( Table 7). Furthermore, the difference in the presence of the crystallographically distinct Cu blocks has an influence on the angles of the coordination sphere of Cu and Zn atoms. In the case of 1, the C−S−Cu angles directly bonded with the irregular line of the chain are as follows: C3−S3−Cu2 with value 110.38(12) and C4−S4−Cu3 with value 85.00 (11). For the C−S−Cu angles in 2, there is one value 113.30(12). In 1 as well as in 2, the S−Cu−S angles are 180.0, which indicate the trans positions of the S atoms in Cu blocks. In 1, there is bigger discrepancy for angles included in coordination sphere of Zn, while, in 2, the range of the values of N-Zn-N angles (with one except: the angle N3−Zn1−N3 i ) is more similar (Table S1 and Table S2). The occurrence of N−H•••N beside the N−H•••S hydrogen bond in 1 has the influence on the more compact structure of this part of the chain where they are located, whereas the The shortest distances between paramagnetic copper ions are comparable in the both structures and show values as follows: 7.569, 8.481, 8.663 and 8.249, 8.263 Å for 1 and 2, respectively. The intermetallic value describing separation between copper and zinc ions in the chain of 2 is much longer (6.879 Å) than the Cu−Zn distances in 1 (5.0391(5) and 6.3630(6) Å) (Table 7). Furthermore, the difference in the presence of the crystallographically distinct Cu blocks has an influence on the angles of the coordination sphere of Cu and Zn atoms. In the case of 1, the C−S−Cu angles directly bonded with the irregular line of the chain are as follows: C3−S3−Cu2 with value 110. 38(12) and C4−S4−Cu3 with value 85.00 (11). For the C−S−Cu angles in 2, there is one value 113.30(12). In 1 as well as in 2, the S−Cu−S angles are 180.0, which indicate the trans positions of the S atoms in Cu blocks. In 1, there is bigger discrepancy for angles included in coordination sphere of Zn, while, in 2, the range of the values of N-Zn-N angles (with one except: the angle N3−Zn1−N3 i ) is more similar (Tables S1 and S2). The occurrence of N−H···N beside the N−H···S hydrogen bond in 1 has the influence on the more compact structure of this part of the chain where they are located, whereas the extended structure is observed if they are missing. This feature does not exist in the case of 2 with only N−H···S hydrogen bonds detected. Furthermore, the non-bridging sulfur atoms in 1 play an important role in maintaining the crystal structure. The same situation takes place in the previously described compound in [19].
The previously described compounds, which show solvatomorphism with the formula [Cu(en) 2  , are also complexes being one-dimensional chains. However, they show different chain topology (Table 7 and Figure 10). As it was observed in 2, in [Cu(en) 2 Zn(NCS) 4 ]·H 2 O, a regular zigzag pattern occurred with a single Cu-Zn distance characterizing the intermetallic separation in the chain. Relatively similar metal arrangement with a zigzag pattern was observed in 1, but the crucial difference relied on two copper units introducing some irregularities with compressed and extended parts of the chain. The structure containing half of the water molecule adopted a helical shape with a turn being 8.269 Å. The helical structure of the coordination polymer affected the Cu-Cu distance with 9.001 Å within the chain compared to shorter distances in zigzags (7.484 in [Cu(en) 2 Zn(NCS) 4 ]·H 2 O, 8.481 (1) and 8.249 Å (2)). The shortest Cu-Cu distances (6.308 Å) occurs in a compound with acetonitrile molecule. However, it is related to interactions between copper(II) ions mediated by only S2 atoms-in this compound, the same thiocyanate transfers coupling between both Cu(II) cations. In the case of Zn-Zn distances, the shortest (8.261 Å) occurs in a compound with half of the water molecule, with the largest being 13.758 Å in 2. It should be noted that, due to zinc positions in zigzags, Zn-Zn interchain distances are usually much shorter than intrachain ones except for a helical structure presenting substantially different metal unit arrangement. This compound has the longest Cu-S bond among the compared complexes. This significant elongation of the Cu ions binding towards sulfur atoms may result from steric hindrance caused by the presence of two methyl substituents beard by nitrogen atoms of the diamine amino group. An additional methyl group attached to a carbon atom in 1 results in very short Cu-S bonds observed also for unsubstituted en molecules in the helical structure [18] and [Cu(en) 2 Zn(NCS) 4 ]·H 2 O [19]. Therefore, it seems that subtle factors such as solvents (its kind and number of molecules) present in the crystal network are even more crucial for Cu-S distances. It is confirmed by a large range of these contacts for en complexes ranging from 2.921 Å to 3.232 Å [18]. On the contrary, Cu-N bonds usually depend on the substituents attached to nitrogen atoms with the longest distances found for 2, whereas these bonds in pn and en complexes are similar. The helical structure is exceptional because it shows huge asymmetry with very short and very long Cu-N bonds. In the latter case, they are such length as for the unsubstituted ligand as for N,N-Me 2 -en with two nitrogen atoms bearing two methyl groups in 2.

Conclusions
In this paper, we presented three new heterometallic compounds with the formula [Cu(diamine) 2 Zn(NCS) 4 ]·nH 2 O (diamine / n = pn / 0; N,N-Me 2 -en, 0; N-Me-en, 1 2 ) were characterized by elemental analysis, IR, electronic, and EPR spectra, single crystal XRD, and magnetic studies. At least in two cases, 1D chains were detected with thiocyanates acting as bridges. In these cases, Cu-S elongated coordination bonds complete the copper(II) spheres resulting in 4 + 2 coordination. The details of the coordination concerning Cu-S and Cu-N bonds depend on substituent position affecting steric hindrance and hence a topology of the chain revealing different zigzag patterns characterized by one (regular) or two ("irregular") Cu-Zn distance values. Pryma et al. [18] reported two similar chain structures but showing another topology i.e., helical or linear, with different connectivity and/or mutual unit orientations. It proves that even subtle changes of solvent, water molecules numbers, synthesis conditions, and diamine results in the different observed topologies.
Solid state magnetic characterization of [Cu(diamine) 2 Zn(NCS) 4 ]·nH 2 O compounds reveals a ferromagnetic (pn) vs. antiferromagnetic (N,N-Me 2 -en) interactions between paramagnetic copper(II) metal centers. Presumably, the used diamine ligand, shape of the zigzag chain, and hydrogen interactions have the influence on the occurrence and type of magnetic interaction in obtained compounds. Both approaches of treatment of magnetic data, i.e., one-dimensional chain (HDVV) and simple Curie-Weiss models, give similar results (Table 6), which suggests that the interactions through thiocyanato bridges are negligible or comparable with interactions through hydrogen bonds. This is not strange, considering the structural aspects discussed above. Missing magnetic data for structures reported by Pryma et al. [18] impede any magnetostructural correlations.