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Article

The (Bipyridyl)copper(II) Acetate System: (2,2′-Bipyridyl)copper(II) Acetate Pentahydrate (Ribbons of Planar (H2O)6 Rings Fused with Planar (H2O)4 Rings) and (2,2′-Bipyridyl)copper(II) Acetate Acetonitrile Solvate

by
Paul D. Entzminger
,
Edward J. Valente
* and
Eugenijus Urnezius
*
Department of Chemistry & Biochemistry, University of Portland, 5000 North Willamette Blvd., Portland, OR 97203, USA
*
Authors to whom correspondence should be addressed.
Compounds 2026, 6(1), 11; https://doi.org/10.3390/compounds6010011
Submission received: 17 November 2025 / Revised: 18 January 2026 / Accepted: 27 January 2026 / Published: 2 February 2026
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Abstract

Two crystalline complexes, (2,2′-bipyridine)Cu(CH3COO)2·5H2O (3) and (2,2′-bipyridine)Cu(CH3COO)2·CH3CN (4), have been isolated and characterized by low-temperature single-crystal X-ray diffraction experiments. Crystals of phase 3 were studied previously at room temperature (296 K) under conditions leading to rapid desolvation and less distinct characterization of the waters of crystallization. With our redetermination of 3 at 100(2) K, we present a detailed description of ribbon-like structure formed by water molecules in crystals of (2,2′-bipyridine)Cu(CH3COO)2·5H2O. Acetate oxygens are linked by hydrogen-bonding to two inequivalent waters separated by 4.72 Å; the other three water molecules are trapped in polymeric ribbons of anticooperative hydrogen-bonded six-membered rings fused with cooperative hydrogen-bonded four-rings. Water oxygens of the fused ring ribbons associate only with other water oxygens, and this water structure has a local density and pair distribution function which resembles that of liquid water. Crystals of 4 are monoclinic, with acetonitrile of solvation unassociated with the complex. In both 3 and 4, bipyridine planes interleave through π-aryl stacking.

Graphical Abstract

1. Introduction

We stumbled upon the complexity of crystalline phases consisting of 2,2′-bipyridine/(bipy)/copper(II)/acetate/solvent while investigating the reactivity of 2,5-difluoro-1,4-dihydroquinone appended with two –P(=O)(iPr)2 groups towards various (bipy)CuX2 complexes (X = Cl−, BF4−, or CH3COO−) [1]. When (2,2′-bipyridyl)copper(II) acetate hydrate (2) was used as source of (bipy)Cu(II), these reactions also produced crystalline byproducts. Two of them were isolated and determined to be 2,2′-bipyridyl)copper(II) acetate pentahydrate (3), and (2,2′-bipyridine)Cu(CH3COO)2·CH3CN (4). Complex 3 described as a colorless solid, together with its room temperature structure, has been reported earlier [2]. Many systematic studies of chelating systems (metal ion, carboxylate, bidentate N-donor, solvent) have been described [2,3,4,5,6,7,8,9,10,11,12,13,14], and the evidence from the literature suggests that systems composed of 2,2′-bipyridine (bipy), copper(II), and acetate display diverse structural possibilities. While 2,2′-bipyridine and similarly o-phenanthroline are predictably bidentate ligands to copper(II) [4,5,7,8,11,12], carboxylates are also known for monodentate and bridging coordination [8]. The molecular structures from crystal studies of (bipy)copper(II) acetate include a report on an anhydrous form 1 [9] and a monohydrate (actually a dimer dihydrate) 2, Scheme 1 [10,11]. Compound 1, a neutral monomeric complex, probably contains a distorted six-coordinate copper(II), with a bidentate bipyridyl ligand and two unsymmetrical bidentate acetate ligands. A synthesis of this phase was not successful (vide infra) in our hands. Each copper(II) in the dimer dihydrate 2 has a bidentate bipyridyl ligand, a bidentate acetate, and two bridging monodentate acetates for six-coordination [11]. The water of crystallization does not coordinate with copper(II). A polymeric form of “(bipy)Cu(acetate)” [11], formed from 1 with added bipyridine and acetonitrile, is a tetra-acetoxy bridged copper(II) dimer linked through two monodentate μ-acetates with a dinuclear (bipy)Cu(acetate). The structure amounts to {-[Cu2(acetate)4](acetate)[Cu2(bipy)2(acetate)2] (acetate)-}, and the overall stoichiometry is neutral [(bipy)1/2Cu(acetate)2] [11].
Compound 3 is a very water-soluble phase and can be made directly with stoichiometric mixtures of complex components crystallizing from water/dimethylformamide (10:1) or from solutions of 2 in water on evaporation (see Figure S1). As will be discussed below, this pentahydrate is particularly wet for a coordination complex without coordinated water, and partially desolvates over the course of a few days from deep blue crystals in contact with the crystalizing solutions drying in air to form light crystals of blue dimer dihydrate (2). Since previous structure determination was carried out at room temperature, we thought it was best to undertake a redetermination of the structure of 3 at low temperature (100 K) due to the interesting structure of the non-coordinating waters of hydration and the efflorescence of the phase.
Where hydrate 2 is dehydrated by heating and the residual is recrystallized from acetonitrile, a monomer (bipy)copper(II) acetate acetonitrile solvate (4) forms blue crystals on slow evaporation of acetonitile absent access to atmospheric humidity. In this work, we characterize these two monomeric (bipy)copper(II) acetates (3, 4) at low temperatures.

2. Experimental Procedures

2.1. Syntheses

Reagents and solvents were obtained from VWR Corp (Wayne, PA, USA), Sigma-Aldrich Corp (St. Louis, MO, USA), and TCI America (Portland, OR, USA) and used as received. IR spectra were measured on a Nicolet iS10 FT-IR spectrometer with ATR adapter (Thermo Fisher Scientific, Waltham, MA, USA) running Omnic software (version 9.8.372) [15].
(2,2′-Bipyridyl)copper(II) acetate (anhydrous), 1. Following the method in [9], copper(II) acetate hydrate (1.0 equivalent) and 0.67 equivalents of bipyridine were dissolved in acetonitrile, which then slowly formed a pale blue-green crystalline precipitate. This was identified as the dimer dihydrate 2, rather than the anhydrous form. This phase was characterized by crystallography: crystals of 2 at 295 K are triclinic, P-1, with a = 7.8064 Å, b = 8.8695 Å, c = 12.1838 Å, α = 101.609°, β = 105.976°, γ = 106.641°, and V = 740.26 Å3 [11].
(2,2′-Bipyridyl)copper(II) acetate pentahydrate, 3. Dimer dihydrate 2 (vide infra) was dissolved in water or in water/dimethylformamide (10:1) to form a deep blue solution. On evaporation at ambient temperature, rods with lengths greater than 1–2 cm formed (Figure S1). The crystals are stable indefinitely if allowed to remain in contact with their crystallizing liquor, but lose water to form dull blue phase 2 on efflorescence in dry air (Figure S1). Water could be replaced with D2O by reconstituting phase 3 by dissolving 2 in D2O and slowly evaporating the solution. Key IR vibrations associated with the water νOH (and ν OD) bands are shown in Figures S2 and S3.
(2,2′-Bipyridyl)copper(II) acetate acetonitrile solvate, 4. Blue crystals of the dimer dihydrate 2 were heated briefly to drive water away, and the resulting grayish-white solid was dissolved in acetonitrile to form a blue solution. Evaporation of the solvent at ambient temperature produced small light blue prisms of 4. The crystals are stable indefinitely in the atmosphere.

2.2. Crystallography

A representative crystal of 3 was retrieved from its aqueous liquor and snagged with a nylon loop and quickly transported to the goniometer which had previously been cooled to 100(2) K. From experience, crystals of 3 selected at leisure, mounted conventionally on a fine glass fiber, and examined at 296 K for several hours resulted in a small amount of sample decomposition. None is observed when handled at lower temperatures. Data were collected on an Oxford-Rigaku Gemini diffractometer [16]. The structures were solved and refined with SHELX programs [17]. Non-hydrogen atoms were refined with anisotropic librational parameters, and ligand hydrogens were placed at calculated positions. Water hydrogens were located in difference Fourier maps and are ordered; their locations were allowed to refine with the restraint that the O-H distances were 0.84(2) Å, representing the usual distance bias owing to the inadequacy of the spherical atom model, distortion of the location of O-H bond density, and librational anisotropy. For hydrogens, the associated isotropic librational factors were set to 150% of the equivalent isotropic librational factors of the attached non-hydrogen atoms. The H-O-H interbond angles were refined to 105.6(16)°. When the refinement was unrestrained, mean O-H distances became 0.77(5) Å, which is within the large estimated uncertainty of the usual biased value, and the mean angle subtended at water oxygens was 104.9(15)°, which agrees with the accepted value for isolated water at 104.5°. A summary of the data collection and refinement details is given in Table 1. Methyl hydrogens are ordered. Final difference maps showed that the major residual electron density peaks were near bond saddle points. At 296(1) K, compound 3 gave cell constants a = 7.066(5) Å, b = 12.437(11) Å, c = 12.943(9) Å, α = 114.39(7)°, β = 100.94(6)°, and γ = 96.74(7)°. For comparison, the study [2] gave a = 7.056(2) Å, b = 12.4461(9) Å, c = 12.9342(10) Å, α = 114.443(2)°, β = 100.752(2)°, and γ = 96.716(2)°. The a axis contracts by 2.0% on cooling to 100(2) K, while the b and c axes were less than 0.7% shorter. Data collection was carried out on crystals of 4 similarly, and no visible evidence of crystal desolvation was observed. Absorption corrections were applied to both data sets. Drawings of the structures were prepared with Mercury software (version 2025.1.1) [18].

3. Discussion

There are now three structures known for monomeric (bipy)copper(II) acetate. Little can be told about the parent non-hydrated form 1, as the original study could not be repeated and metrics relevant to this phase were unavailable [11]. Here, we report the monomer in a low-temperature redetermination of the pentaquo solvate (3), and an acetonitrile solvate (4). The asymmetric units of complex 3 are given in Figure 1, and for complex 4 in Figure 2. Copper(II) ions in 3, 4, and 1 are six-coordinate, described by distorted octahedrons. Axial and equatorial acetate oxygens of the bidentate acetates show considerably unsymmetrical Cu-O lengths (Jahn–Teller distortions). The axial lengths are longer than the equatorial by about 0.6 Å, while the Cu-N(bipy) bond lengths among the monomeric complexes are within 0.04 Å (Table 2).

3.1. Water and the Crystal Structure of the Pentahydrate Compound 3

This phase contains discrete (bipy)copper(II) acetate complexes in general positions of space group P-1. Water oxygens are not coordinated to the copper(II) ion, but two (of the five) have hydrogen-bonding interactions with the coordinated acetate oxygens. Cell volumes of the various (bipy)copper(II) acetate phases are instructive on the nature of the waters of crystallization. The density of the dimer dihydrate (2) (Z = 1, complexes on inversion centers of P-1) is 1.626 Mg/m3 (130 K) [12] and 1.624 Mg/m3 (295 K, cell reported above). The monomeric form 1 described in the literature has a similar density, calculated to be 1.623 Mg/m3 (293 K) [9]. An implied dehydration of the dimer dihydrate 2 therefore could involve a cell volume decrease (740 Å3 in 2 to 690 Å3 in 1) consistent with a loss of about two waters per cell (~50 Å3) from the ambient temperature determinations. Atom coordinates were not supplied or deposited for 1, so this cannot be checked further. In contrast, the density of monomeric pentahydrate 3 is calculated to be 1.479 Mg/m3 (100 K) and 1.432 Mg/m3 (296 K). At 296 K for 3, this involves an increase of 301 Å3 (for 10 waters in the triclinic unit cell) relative to the monomeric anhydride 1. This difference (30.1 Å3 per water) implies a local density of the water clusters in 3 of 0.994 Mg/m3, similar to the values found for the crystalline water(s) of pig lysozyme (30.23 Å3) [19], and liquid water (29.92 Å3, density 0.9970 g/cm3 at 298 K). In contrast, ice has a water volume of 32.64 Å3 and a density of 0.934 g/cm3. This is similar to that found in a nickel(II) complex containing water dodecamers (volume of 309 Å3 per water decamer at 143 K), which appear as ice-like clusters and have a water density of 0.967 g/cm3 [20,21].
The five water molecules in the asymmetric units of 3 cluster around centers of symmetry in the triclinic space group, P-1. Three of the five (O1W, O2W, O3W) and their inversion relatives form a nearly planar anticooperative hydrogen-bonded and slightly elongated hexagon [by centrosymmetry, O…O distances 2.8504(19) Å, 2.766(2) Å, 2.8001(19) Å, angles of 109.23°, 118.11°, 132.65°, with torsions of 1.56°, −1.31°, 1.68°]. This hexamer is fused to a rigidly planar cooperative hydrogen-bonded rectangle of water oxygens O1W, O2W centered on a −1 site with O…O distances of 2.766(2) Å and 2.791(2)Å, and angles of 89.78°, 90.22° (Figure 3). Together, the rings form an infinite ladder with alternating six- and four-membered fused hydrogen-bonded rings. Waters O3W of the six-ring are not shared between rings but are hydrogen-bonded to two inequivalent exo-waters [O4W and O5W, O…O distances 2.6564(19) Å and 2.752(2) Å] which then donate pairs of hydrogen bonds to acetate ligand oxygens [O1 and O2, O…O distances 2.8023(18) Å and 2.7951(19) Å] (Figure 4) of translation relatives of the complex ion. This laddered water structure is a corrugated water column or tape extending through the structure along the crystallographic a axis with an inter-ring angle of 42.08°. Ring hydrogen bonds are ordered, and this is assisted by the carboxylate oxygens, which are acceptors only. Thus, O4W and O5W only donate hydrogen bonds to the acetates and accept hydrogen bonds from the double donors O3W (and inversion relative). In the six-ring, the hydrogen-bonding motif is R66(12) with O3W as a double acceptor, O2W as a single acceptor and single donor, and O1W as a double donor [22]. In the four-ring, the hydrogen-bonding motif is R44(8), with O2W and O3W being single donors and single acceptors. Water molecules have three or four oxygen neighbors, and the waters of the fused ring tape make hydrogen bonds only with other waters. Possibly, O1W has a weak contact with H-C5(bipy).
In the extended structure of 3, the bipyridyl ligands are packed in an extended π-π array with a spacing of 3.463 Å along the crystallographic a axis (3.42 Å in graphite [23]) (Figure 5). The laddered waters in their channels ran parallel with the stacked complexes (Figure 3). The O1…O2(acetate) inter-complex ion spacing was 4.719 Å. The a axis of 3 showed the largest temperature-dependent decline (2.0%), while the other two axes were barely a third as large (0.7%) on cooling from 296 K to 100 K (cell information vide infra). In phase 4, the same bipyridyl packing was found as in 3 (compare Figure 6 with Figure 5) with this packing approximately normal to [−1 2 2] planes of the monoclinic cell. The molecular volumes of the monomeric complex, taken from the cell volumes with less water or acetonitrile volumes, were calculated to be 330 Å3 (3), 346 Å3, (296 K, [2]), 346 Å3 (1), and 358 Å3 (4).

3.2. Non-Bonded Interactions

For the water (w) and carboxylate (c) oxygen components of phase 3, we have extracted the non-bonded Ow,c…Ow,c pair distribution function at 0.1 Å increments (Figure S4). As in liquid water, there was an Ow…Ow peak at about 2.6–2.8 Å separation for contacts within hydrogen-bonding distances [24,25,26]. In 3, this was followed by a 3.8–4.0 Å Ow…Ow peak associated with next nearest neighbors in four-rings. Then, a broad group from 4.4 to 5.1 Å was associated with six-ring 1,3-contacts and other second neighbors. The contribution from Oc…Ow at the hydrogen-bonded distance was in the shorter hydrogen-bonded group, as expected. The O…O contacts in 3 were somewhat related to those identified in bulk liquid water modeled with a cage structure [24]. The 3.8–4.0 Å contacts were muted in water compared to phase 3, which has four-ring contributors [24,27]. In general, the liquid water radial O…O distributions showed a pronounced nearest neighbor peak (2.8 Å), followed by a second broad peak from 3.2 to 5.3 Å (near ambient temperature) [27,28]. In 3, the O…O contacts from 3.6 to 5.1 Å were in this broad envelope. In Figure S4, the O…O distributions have been overlaid with the C…Ow,c pair distribution. The shortest non-bonded C…O contact in 3 was 3.144 Å (aryl bipyridyl C to acetate O), just less than the van der Waals contact distance; all others were longer.
The waters of phase 3 amount to 21.1% of the mass of the contents of the unit cell. The waters are isolated in the ladders (vide infra) and contact the complex ion through hydrogen-bonding with a non-ladder water, which hydrogen-bonds with the carboxylate oxygens. How does this exceptionally hydrated structure compare with other reported hydrates? A survey of recent structures (Refs. [29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46]) has been undertaken with the results summarized in a survey in Table S1. These include four- and six-ring water clusters, which may employ coordinated or uncoordinated (in the case of metal ions) water and ligand oxygens. Four-ring structures are very nearly planar (or exactly planar if required by inversion symmetry in many cases). Six-ring water structures are more varied in conformation. Water content ranges from 6.4% to 24.1% for the 21 surveyed water-cluster phases, and phase 3 (entry P) is second-highest in the survey. The water of entry I bears some structural resemblance to phase 3; it is an organic water clathrate with additional waters of crystallization. Its six-ring is nearly planar, composed only of waters of crystallization, and with cooperative hydrogen bonds [29]. Another planar six-ring structure is found in entry H (11.0% water), a zinc(II) complex, where the waters of the hexagon are each hydrogen-bonded (both donors and acceptors) with carboxylate oxygens of the complex [30]. Entry J (24.8% water) is an organic compound with waters of crystallization in space group R -3 (#148), which shows a pair of inversion-related planar six-rings with six fused (planar) four-ring sides. Half of the twelve waters are hydrogen-bonded to host nitrogen acceptors [31]. In contrast, entries K (9.2% water) [33], L (9.4% water) [34], M (12.4% water) [34], N (9% water) [35], O (0% water) [36], Q (16.8% water) [37], and S (6.9% water) [38] all have chair-structured six-rings, and of these, only entry Q, a hetero-organic amine, forms the coordinated hydrogen-bonded six-ring only with waters. Computations on isolated water hexamers show the importance of these types of aggregates in the structures of water [36,47,48]. The isolated chair water hexamer was found to be the most stable of a variety of related structures. The planar conformation is usually not included in these comparisons.

3.3. Infrared Spectrum of Phase 3

The higher energy end of the infrared spectra of the solid 3 could be deconvoluted and showed five νOH peaks from the broad profile of the 3200–3700 cm−1 region (Figure S2). On recrystallization of phase 3 in D2O, the infrared spectrum again showed five broadened peaks shifted to lower frequency (Figure S3) consistent with the H/D isotope replacement. The vOD peaks are broadened, and the average H/D ratio observed was 1.390. For comparison, in liquid water, νOH/D is 3490 (2540), νOH/D is 3280 (2450) cm−1, and H/D ratios from water are 1.374 and 1.339, with an average of 1.356. Other infrared bands for phase 3 were unaffected by deuterium exchange.

4. Conclusions

Re-examining the single-crystal diffraction structure of (bipy)Cu(CH3COO)2·5H2O using X-ray diffraction data collected on a sample at 100 K allowed for better assessment of intricate water aggregates present in the solid. A ribbon-like structure formed by H2O molecules in (bipy)Cu(CH3COO)2·5H2O is compared to known structural motifs reported for (H2O)n fragments in other crystalline substances with heavy water content. Our study suggests that coordination complexes composed of 2,2′-bipyridine, Cu(II), and two carboxylate ligands may serve as a fertile ground for other (H2O)n clusters. The packing of the monomer complexes is remarkably similar between the two structures, their metal ions are unsolvated, and their solvation components are distinct from the complex structures.

Supplementary Materials

The following supporting information can be downloaded at https://www.mdpi.com/article/10.3390/compounds6010011/s1, Figure S1: Pictures of fully hydrated and dehydrated samples of complex 4; Figure S2: Infrared spectrum of slightly aged sample of pentahydrate 3 in the 3000–3800 cm−1 range; Figure S3: Infrared spectrum of fresh pentahydrate 3 recrystallized from D2O in the 1900–2900 cm−1 range; Figure S4: Non-bonded pair distributions for C…O and O…O contacts in 3; Table S1: A survey of 4-ring and 6-ring water cluster types found in crystal environments. Additional supporting materials have been deposited for this publication. Crystallographic information has been deposited with Cambridge Crystallographic Data Centre (see Table 1).

Author Contributions

Methodology, P.D.E., E.J.V. and E.U.; Software, E.J.V.; Formal analysis, P.D.E., E.J.V. and E.U.; Investigation, P.D.E.; Resources, E.J.V. and E.U.; Data curation, E.J.V. and E.U.; Writing—original draft, E.J.V.; Writing—review & editing, P.D.E. and E.U.; Supervision, E.U. All authors have read and agreed to the published version of the manuscript.

Funding

Authors acknowledge the National Science Foundation (MRI #0604188) for a grant for crystallographic equipment.

Data Availability Statement

The data presented in this study are openly available in Cambridge Crystallographic Data Center (CCDC deposition numbers 2477031 (compound 3) and 2477032 (compound 4).

Conflicts of Interest

The authors declare no conflicts of interest.

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Compounds 06 00011 sch001
Scheme 1. Formation of some (2,2′-bipyridyl)copper(II) acetates.
Scheme 1. Formation of some (2,2′-bipyridyl)copper(II) acetates.
Compounds 06 00011 sch001
Compounds 06 00011 g001
Figure 1. Ellipsoid plot (50% probability) of the asymmetric unit of (bipyridyl)copper(II) acetate pentahydrate (3).
Figure 1. Ellipsoid plot (50% probability) of the asymmetric unit of (bipyridyl)copper(II) acetate pentahydrate (3).
Compounds 06 00011 g001
Compounds 06 00011 g002
Figure 2. Ellipsoid plot (50% probability) of the asymmetric unit of (bipyridyl)copper(II) acetate acetonitrile solvate (4).
Figure 2. Ellipsoid plot (50% probability) of the asymmetric unit of (bipyridyl)copper(II) acetate acetonitrile solvate (4).
Compounds 06 00011 g002
Compounds 06 00011 g003
Figure 3. Water ribbon structure in 3; the horizontal direction is approximately the crystallographic a axis.
Figure 3. Water ribbon structure in 3; the horizontal direction is approximately the crystallographic a axis.
Compounds 06 00011 g003
Compounds 06 00011 g004
Figure 4. Connectivity of water ribbon to (bipy)Cu(CH3COO)2 units in the structure of 3. Hydrogen bonds are represented by dotted lines.
Figure 4. Connectivity of water ribbon to (bipy)Cu(CH3COO)2 units in the structure of 3. Hydrogen bonds are represented by dotted lines.
Compounds 06 00011 g004
Compounds 06 00011 g005
Figure 5. Stacking of complex cations in 3; the horizontal direction is approximately the crystallographic a axis.
Figure 5. Stacking of complex cations in 3; the horizontal direction is approximately the crystallographic a axis.
Compounds 06 00011 g005
Compounds 06 00011 g006
Figure 6. Stacking of complex cations in 4; the horizontal direction is approximately normal to [−1 2 2] planes.
Figure 6. Stacking of complex cations in 4; the horizontal direction is approximately normal to [−1 2 2] planes.
Compounds 06 00011 g006
Table 1. Crystal data and structure refinement for (2,2′-bipyridyl)copper(II) acetate pentahydrate (3) and acetonitrile solvate (4) 1.
Table 1. Crystal data and structure refinement for (2,2′-bipyridyl)copper(II) acetate pentahydrate (3) and acetonitrile solvate (4) 1.
Compound34
CCDC deposition number24770312477032
FormulaC14H14CuN2O4·5 H2OC14H14CuN2O4·C2H3N
Formula weight g/mol427.89378.87
Temperature K100(2)105(2)
Crystal systemTriclinicMonoclinic
Space groupP-1 (#2)P 2(1)/c (#14)
Radiation: molybdenum; Å0.710730.71073
Cell dimensions
a Å6.9252(5)11.7202(14)
b „12.3844(8)18.8566(16)
c „12.8498(9)8.1151(7)
α degrees114.869(7)90.000
β „100.207(6)100.894(11)
γ „96.758(6)90.000
Volume Å3960.97(13)1761.1(3)
Z, Z’2, 24, 1
Density Mg/m31.4791.429
Absorption coefficient mm−11.1841.267
F(000)446780
Crystal size, mm1.03 × 0.21 × 0.100.40 × 0.23 × 0.12
Data range, θ, degrees3.32 to 32.263.55 to 32.30
Data collected, unique, Rint12,558, 6196, 0.029819,160, 5795, 0.0674
Data, I > 2σI55973932
Parameters, restraints265, 10217, 0
Refinement methodFull-matrix least-squares, F2Full-matrix least-squares, F2
Goodness of fit1.0451.033
R1, wR2 for I > 2 σI0.0324, 0.08580.0501, 0.1085
R1, wR2 for all data0.0378, 0.08890.0865, 0.1309
Difference ρ, max, min; e·Å−3+0.580, −0.830+1.074, −0.845
1 estimated uncertainties in parentheses.
Table 2. Coordination sphere distances in monomeric (bipyridyl)copper(II) acetate structures, in Å.
Table 2. Coordination sphere distances in monomeric (bipyridyl)copper(II) acetate structures, in Å.
CompoundCu-O(acetate), EquatorialCu-O(acetate), AxialCu-N(bipy)
11.927(4), 1.952(4)unreported2.015(5), 2.020(5)
3 (296 K)1.941(3), 1.931(3)2.619(4), 2.745(4)1.989(3), 2.004(3)
3 (100 K)1.9507(17),1.9755(18)2.537(2), 2.611(2)2.005(2), 2.010(2)
41.9371(11), 1.9439(11)2.600(2), 2.753(2)1.9890(13), 2.0024(13)
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Entzminger, P.D.; Valente, E.J.; Urnezius, E. The (Bipyridyl)copper(II) Acetate System: (2,2′-Bipyridyl)copper(II) Acetate Pentahydrate (Ribbons of Planar (H2O)6 Rings Fused with Planar (H2O)4 Rings) and (2,2′-Bipyridyl)copper(II) Acetate Acetonitrile Solvate. Compounds 2026, 6, 11. https://doi.org/10.3390/compounds6010011

AMA Style

Entzminger PD, Valente EJ, Urnezius E. The (Bipyridyl)copper(II) Acetate System: (2,2′-Bipyridyl)copper(II) Acetate Pentahydrate (Ribbons of Planar (H2O)6 Rings Fused with Planar (H2O)4 Rings) and (2,2′-Bipyridyl)copper(II) Acetate Acetonitrile Solvate. Compounds. 2026; 6(1):11. https://doi.org/10.3390/compounds6010011

Chicago/Turabian Style

Entzminger, Paul D., Edward J. Valente, and Eugenijus Urnezius. 2026. "The (Bipyridyl)copper(II) Acetate System: (2,2′-Bipyridyl)copper(II) Acetate Pentahydrate (Ribbons of Planar (H2O)6 Rings Fused with Planar (H2O)4 Rings) and (2,2′-Bipyridyl)copper(II) Acetate Acetonitrile Solvate" Compounds 6, no. 1: 11. https://doi.org/10.3390/compounds6010011

APA Style

Entzminger, P. D., Valente, E. J., & Urnezius, E. (2026). The (Bipyridyl)copper(II) Acetate System: (2,2′-Bipyridyl)copper(II) Acetate Pentahydrate (Ribbons of Planar (H2O)6 Rings Fused with Planar (H2O)4 Rings) and (2,2′-Bipyridyl)copper(II) Acetate Acetonitrile Solvate. Compounds, 6(1), 11. https://doi.org/10.3390/compounds6010011

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