Marijana Dakovic | University of Zagreb (original) (raw)
Papers by Marijana Dakovic
Transition Metal Chemistry, Oct 15, 2010
Cobalt(II) and copper(II) complexes of 3-hydroxypicolinamide (3-OHpia), namely [Co(3-OHpia)2(H2O)... more Cobalt(II) and copper(II) complexes of 3-hydroxypicolinamide (3-OHpia), namely [Co(3-OHpia)2(H2O)2](NO3)2 (1), [Co(3-Opia)2(H2O)2] (2) and [Cu(3-OHpia)2(NO3)2] (3), were prepared and characterized by IR spectroscopy and TG/DTA methods. The molecular and crystal structures of 1 and 3 were determined by X-ray crystal structure analysis. Complexes 1 and 3 were obtained by reaction of 3-hydroxypicolinamide with cobalt(II) nitrate or copper(II) nitrate, respectively, in a
CrystEngComm
Crystal screening by varying isonicotinamide content added to Ni(ii) thiocyanate in water led to ... more Crystal screening by varying isonicotinamide content added to Ni(ii) thiocyanate in water led to seven nickel complexes, whose structure and altered stoichiometries were analyzed by X-ray diffraction, NMR and IR spectroscopies, and DFT calculations.
Acta Crystallographica Section A Foundations and Advances
Recently, the traditional way of perceiving crystalline matter as static and brittle has started ... more Recently, the traditional way of perceiving crystalline matter as static and brittle has started to change, and nowadays we are witnessing a growing number of examples were crystals display a plethora of flexible response to a variety of stimuli. They were found to move, jump, split, flex, twist, curl, explode, or to display a salient behaviour under UV radiation or heating, but lately they were also found to respond to the applied external mechanical force [1]. Organic molecular crystals present a majority of examples of crystal adaptability to external stimuli, whilst metal-organic adaptable crystals are still quite rare. In the first report on mechanical flexibility of coordination polymers we have shown that crystals of a family of Cd(II) coordination polymers are capable of displaying not only exceptional mechanical elasticity but also variable flexible responses to applied external pressure [2]. They can actually differently tolerate exerted force and the different tolerability is a result of slight differences in the importance of intermolecular interactions in crystal packing. We the aim to understand the feature more deeply and to shed light on the underlying principles of the phenomenon, we have recently discovered unprecedented difference in plasticity of crystals of closely related class of Cd(II) coordination polymers [3]. In addition to variable plasticity, crystals also display remarkable pliability and ductility, not hitherto observed for metal-containing molecular crystals, which we present herein. To understand the phenomenon and rationalize observations, in addition to micro-focus SCXRD and AFM, we have also performed a series of custom-designed experiments and complemented those with an in-depth theoretical analysis. The results pointed at intermolecular interactions as the crucial structural feature in determining the type and extent of these highly unusual mechanical responses of crystalline metal-based polymeric materials. Figure 1. Pulling a crystal through sets of metal supporters; crystal immediately straighten as being upon pulled out.
Chemistry of Materials
Metrics & More Article Recommendations A n additional sentence has been added to the Acknowledgme... more Metrics & More Article Recommendations A n additional sentence has been added to the Acknowledgments paragraph. The full Acknowledgments paragraph is presented here.
Acta Crystallographica Section A Foundations and Advances, 2021
Controlling supramolecular synthetic output, with the aim to achieve targeted macroscopic propert... more Controlling supramolecular synthetic output, with the aim to achieve targeted macroscopic properties, is the main goal of crystal engineering.[1] Mechanical flexibility, as one of the highly desired properties of functional materials, has recently become a feature of a growing number of crystalline compounds.[2-5] Plastic deformation, together with elastic response, is frequently observed among organic molecular crystals,[3] but quite rarely noticed among crystalline metal-organic compounds.[4,5] Since the introduction of metal cations to organic systems allow us to achieve specific properties such as magnetic and electric ones, and therefore opens a wide range of possible applications, it is clear that there is a need for determining structural requirements that need to be fulfilled to equip metal-organic crystals with mechanical flexibility. Recently, it was shown that cadmium(II) coordination polymers equipped with halopyrazine ligands adaptably respond to applied external stimuli, displaying elastic flexibility.[5] It was observed that introducing a slight structural changes, simply by exchanging bridging halide anion or halogen atom on halopyrazine ligand, changes the extent of elastic response significantly, while the quantification of their mechanical behaviour clearly showed that they can be categorized into three main subgroups, highly, moderately and slightly elastic. To get an invaluable insight into the phenomenon, we decided to systematically examine similar classes of coordination polymers by introducing slight structural differences through the exchange of supramolecular functionalities only. Herein we opted for pyridine-based ligands decorated with cyano functionality to explore their impact on macroscopic mechanical output. It was determined that the position of cyano group on pyridine ring, as well as used bridging halide anion, dictate the nature and extent of mechanical response. For crystals that displayed elastic behaviour, the responses were quantified and correlated with structural features, primarily the strength and geometry of supramolecular interactions, and compared with the mechanical behaviour of similar metal-containing systems.
The design of desired supramolecular architectures requires deep and clear understanding of supra... more The design of desired supramolecular architectures requires deep and clear understanding of supramolecular interactions and the fine balance between them. Hydrogen bond has already been extensively studied in this context, and many useful strategies for effective supramolecular synthesis based on this particular interaction have been reported. Halogen bond, on the other hand, has only recently been recognized as a useful structure- directing interaction, and several guidelines for selectivity of halogen-bonding interaction in the assembly process of organic solids have been suggested. The understanding of halogen- bonding interaction in molecular recognition processes of metal-containing systems are still at an early stage of development. Here we have prepared and structurally characterized a series of hexafluoroacetylacetonate (hfac) complexes of Co(II), Ni(II) and Cu(II) with 3-iodopyridine with idea to explore the selectivity of the halogen-bonding interaction in the metal- conta...
It has been shown that NO2···NO2 interactions are comparable in strength to weak hydrogen bonds a... more It has been shown that NO2···NO2 interactions are comparable in strength to weak hydrogen bonds and can have a structure determining role in assembling organic molecules that lack stronger halogen or hydrogen bond donors and acceptors. Nitro groups are often found in nitrogen rich energetic materials where they generally contribute to destabilization of the material resulting in its thermal, shock or mechanical instability. While it is highly unlikely that NO2···NO2 interactions will ever be used as a crystal engineering tool for the design of energetic materials, better understanding of these interactions could further unveil the correlation between structure and properties of energetic materials. We have prepared a series of hexafluoroacetylacetate complexes with 3- nitropyridine, e.g. the complexes of cobalt(II), nickel(II) and copper(II), to investigate the structure directing potential of NO2···NO2 interactions in assemblies of metal-organic systems in the absence of stronger h...
CrystEngComm, 2020
The crystal structures of six novel Ag+ complexes with NO3− and dihalopyridines revealed intrigui... more The crystal structures of six novel Ag+ complexes with NO3− and dihalopyridines revealed intriguing differences that were interpreted by DFT calculations.
Acta Crystallographica Section A Foundations and Advances, 2019
Research based on Margaret Etter's Rules [1] has shown that hydrogen and halogen bond donor-accep... more Research based on Margaret Etter's Rules [1] has shown that hydrogen and halogen bond donor-acceptor pairings follow a hierarchy based on their strengths which can be correlated with calculated molecular electrostatic potential (MEP) values. Studies conducted on organic systems have shown that it is possible to predict the donoracceptor pairing if the difference in MEP values is significant. It still remains to be determined if insights obtained for organic systems can be used in a tandem with metal centers. We have shown in our previous work that MEP values can be used to rationalize the supramolecular connectivity in the metal-organic setting for both hydrogen [2] and halogen [3] bonds. We have also shown that it is possible to use MEP values to predict the supramolecular connectivity in 2,4-pentanedionate (acac)-based complexes (Ni II , Co II , Cu II), equipped with the lactam moiety [4]. The goal of our current research is to determine if it is possible to use MEP values to predict the supramolecular connectivity in systems displaying more conformational freedom. To assess this hypothesis, we used acac-based complexes of Co(II) and Ni(II) with small heterocyclic ligands equipped with the amide functionality, and here we are reporting on the results.
Acta Crystallographica Section E Crystallographic Communications, 2020
A 6-chloronicotinate (6-Clnic) salt of a one-dimensional cationic nickel(II) coordination polymer... more A 6-chloronicotinate (6-Clnic) salt of a one-dimensional cationic nickel(II) coordination polymer with 4,4′-bipyridine (4,4′-bpy), namely, catena-poly[[[tetraaquanickel(II)]-μ-4,4′-bipyridine-κ2 N:N′] bis(6-chloronicotinate) tetrahydrate], {[Ni(C10H8N2)(H2O)4](C6H3ClNO2)2·4H2O} n or {[Ni(4,4′-bpy)(H2O)4](6-Clnic)2·4H2O} n , (1), was prepared by the reaction of nickel(II) sulfate heptahydrate, 6-chloronicotinic acid and 4,4′-bipyridine in a mixture of water and ethanol. The molecular structure of 1 comprises a one-dimensional polymeric {[Ni(4,4′-bpy)(H2O)4]2+} n cation, two 6-chloronicotinate anions and four water molecules of crystallization per repeating polymeric unit. The nickel(II) ion in the polymeric cation is octahedrally coordinated by four water molecule O atoms and by two 4,4′-bipyridine N atoms in the trans position. The 4,4′-bipyridine ligands act as bridges and, thus, connect the symmetry-related nickel(II) ions into an infinite one-dimensional polymeric chain extending...
Acta Crystallographica Section E Crystallographic Communications, 2020
A copper(II) dimer with the deprotonated anion of 2-bromonicotinic acid (2-BrnicH), namely, tetra... more A copper(II) dimer with the deprotonated anion of 2-bromonicotinic acid (2-BrnicH), namely, tetrakis(μ-2-bromonicotinato-κ2 O:O′)bis[aquacopper(II)](Cu—Cu), [Cu2(H2O)2(C6H3BrNO2)4] or [Cu2(H2O)2(2-Brnic)4], (1), was prepared by the reaction of copper(II) chloride dihydrate and 2-bromonicotinic acid in water. The copper(II) ion in 1 has a distorted square-pyramidal coordination environment, achieved by four carboxylate O atoms in the basal plane and the water molecule in the apical position. The pair of symmetry-related copper(II) ions are connected into a centrosymmetric paddle-wheel dinuclear cluster [Cu...Cu = 2.6470 (11) Å] via four O,O′-bridging 2-bromonicotinate ligands in the syn-syn coordination mode. In the extended structure of 1, the cluster molecules are assembled into an infinite two-dimensional hydrogen-bonded network lying parallel to the (001) plane via strong O—H...O and O—H...N hydrogen bonds, leading to the formation of various hydrogen-bond ring motifs: dimeric R ...
Crystal Growth & Design, 2019
A crystalline cadmium(II) coordination trimer with pyridine-4-propanamide (4-propy), [Cd 3 Cl 4 (... more A crystalline cadmium(II) coordination trimer with pyridine-4-propanamide (4-propy), [Cd 3 Cl 4 (H 2 O) 4 (4propy) 6 ](CH 3 CH 2 COO) 2 , readily responds to external stimuli while preserving crystal integrity. Two polymorphic forms, Polymorph-I (triclinic form) and Polymorph-II (monoclinic form), undergo a reversible single-crystal-tosingle-crystal conformational polymorph transformation upon temperature change, while the triclinic form (Polymorph-I) additionally shows substantial reversible sorption/desorption potential via two pathways, in response to stimulation by (i) elevated temperature, and (ii) reduced pressure. The elucidation of the conformational transformation via a variety of ex situ and in situ methods (SCXRD, VT-PXRD, TG/DSC and VT-IR), complemented by in-depth theoretical studies, suggested that the conformational transformation might be a process that occurs slowly and continuously over a wider temperature range, with different processes (distinctive conformational changes) taking place over different temperature intervals.
IUCrJ, 2018
In order to develop transferable and practical avenues for the assembly of coordination complexes... more In order to develop transferable and practical avenues for the assembly of coordination complexes into architectures with specific dimensionality, a strategy utilizing ligands capable of simultaneous metal coordination and self-complementary hydrogen bonding is presented. The three ligands used, 2(1H)-pyrazinone, 4(3H)-pyrimidinone and 4(3H)-quinazolinone, consistently deliver the required synthetic vectors in a series of CdII coordination polymers, allowing for reproducible supramolecular synthesis that is insensitive to the different steric and geometric demands from potentially disruptive counterions. In all nine crystallographically characterized compounds presented here, directional intermolecular N-H⋯O hydrogen bonds between ligands on adjacent complex building blocks drive the assembly and orientation of discrete building blocks into largely predictable topologies. Furthermore, whether the solids are prepared from solution or through liquid-assisted grinding, the structural o...
Acta Crystallographica Section A Foundations and Advances, 2016
Figure 1. Elastic bending in crystals of [CdBr 2 (I-pz) 2 ] n .
Acta Crystallographica Section A Foundations and Advances, 2015
Crystal Growth & Design, 2016
Acta Crystallographica Section A Foundations and Advances, 2015
Acta Crystallographica Section A Foundations and Advances, 2015
Crystal Growth & Design, 2016
Molecular electrostatic potential based guidelines for selectivity of halogen-bond interactions w... more Molecular electrostatic potential based guidelines for selectivity of halogen-bond interactions were explored via systematic co-crystallizations of 9 perfluorinated halogen-bond donors and 12 ditopic acceptors presenting two binding sites with different electrostatic potentials. A total of 89 of the 108 reactions resulted in co-crystal formation (as indicated by IR spectroscopy), and 35 new crystal structures were obtained. Methanol was exclusively used as a solvent for crystal growth in order to avoid any potential solvent−solute bias throughout these experiments. The structures were organized into three different groups depending upon the specific nature of the observed halogen-bond connectivities in each case. The electrostatic potential difference between the two acceptor sites on each molecule was defined as the ΔE value. Group 1 comprised acceptor molecules with a ΔE value below 35 kJ/mol units, and in this category halogen bonding took place on both binding sites in all co-crystals (9/9). Ditopic acceptor molecules in Group 2 were characterized by a ΔE value in the 35−65 kJ/mol range, and in this group half the structures showed halogen bonding to the best acceptor (11/22) and half the structures showed halogen bonding to both binding sites (11/22). In Group 3 the ΔE value was >167 kJ/mol, and in all of the co-crystals found herein (7/7), the halogen-bond donor favored the best acceptor site. These results allow us to propose some tentative guidelines and rationales for halogen-bond preferences in competitive systems. If ΔE < 35 kJ/mol, the electrostatic potential difference is not large enough to allow the donor molecules to form halogen bonds of sufficiently different thermodynamic strength to result in any pronounced molecular recognition preference (typically both, or several acceptors are then engaged in halogen bonding). Upon the basis of data produced in this study, in combination with relevant structures from the Cambridge Structural Database, it seems reasonable to suggest that if the ΔE value between two geometrically accessible halogen-bond acceptor sites is greater than 75 kJ/mol, the thermodynamic advantage of forming halogen bonds to the best acceptor provides a strong enough driving force that the best donor consistently interacts with the best acceptor; intermolecular selectivity is the result. However, if the ΔE resides between these two proposed boundaries, the outcome is unpredictable, and other factors are then likely to be responsible for the path that a particular supramolecular reaction will follow.
Transition Metal Chemistry, Oct 15, 2010
Cobalt(II) and copper(II) complexes of 3-hydroxypicolinamide (3-OHpia), namely [Co(3-OHpia)2(H2O)... more Cobalt(II) and copper(II) complexes of 3-hydroxypicolinamide (3-OHpia), namely [Co(3-OHpia)2(H2O)2](NO3)2 (1), [Co(3-Opia)2(H2O)2] (2) and [Cu(3-OHpia)2(NO3)2] (3), were prepared and characterized by IR spectroscopy and TG/DTA methods. The molecular and crystal structures of 1 and 3 were determined by X-ray crystal structure analysis. Complexes 1 and 3 were obtained by reaction of 3-hydroxypicolinamide with cobalt(II) nitrate or copper(II) nitrate, respectively, in a
CrystEngComm
Crystal screening by varying isonicotinamide content added to Ni(ii) thiocyanate in water led to ... more Crystal screening by varying isonicotinamide content added to Ni(ii) thiocyanate in water led to seven nickel complexes, whose structure and altered stoichiometries were analyzed by X-ray diffraction, NMR and IR spectroscopies, and DFT calculations.
Acta Crystallographica Section A Foundations and Advances
Recently, the traditional way of perceiving crystalline matter as static and brittle has started ... more Recently, the traditional way of perceiving crystalline matter as static and brittle has started to change, and nowadays we are witnessing a growing number of examples were crystals display a plethora of flexible response to a variety of stimuli. They were found to move, jump, split, flex, twist, curl, explode, or to display a salient behaviour under UV radiation or heating, but lately they were also found to respond to the applied external mechanical force [1]. Organic molecular crystals present a majority of examples of crystal adaptability to external stimuli, whilst metal-organic adaptable crystals are still quite rare. In the first report on mechanical flexibility of coordination polymers we have shown that crystals of a family of Cd(II) coordination polymers are capable of displaying not only exceptional mechanical elasticity but also variable flexible responses to applied external pressure [2]. They can actually differently tolerate exerted force and the different tolerability is a result of slight differences in the importance of intermolecular interactions in crystal packing. We the aim to understand the feature more deeply and to shed light on the underlying principles of the phenomenon, we have recently discovered unprecedented difference in plasticity of crystals of closely related class of Cd(II) coordination polymers [3]. In addition to variable plasticity, crystals also display remarkable pliability and ductility, not hitherto observed for metal-containing molecular crystals, which we present herein. To understand the phenomenon and rationalize observations, in addition to micro-focus SCXRD and AFM, we have also performed a series of custom-designed experiments and complemented those with an in-depth theoretical analysis. The results pointed at intermolecular interactions as the crucial structural feature in determining the type and extent of these highly unusual mechanical responses of crystalline metal-based polymeric materials. Figure 1. Pulling a crystal through sets of metal supporters; crystal immediately straighten as being upon pulled out.
Chemistry of Materials
Metrics & More Article Recommendations A n additional sentence has been added to the Acknowledgme... more Metrics & More Article Recommendations A n additional sentence has been added to the Acknowledgments paragraph. The full Acknowledgments paragraph is presented here.
Acta Crystallographica Section A Foundations and Advances, 2021
Controlling supramolecular synthetic output, with the aim to achieve targeted macroscopic propert... more Controlling supramolecular synthetic output, with the aim to achieve targeted macroscopic properties, is the main goal of crystal engineering.[1] Mechanical flexibility, as one of the highly desired properties of functional materials, has recently become a feature of a growing number of crystalline compounds.[2-5] Plastic deformation, together with elastic response, is frequently observed among organic molecular crystals,[3] but quite rarely noticed among crystalline metal-organic compounds.[4,5] Since the introduction of metal cations to organic systems allow us to achieve specific properties such as magnetic and electric ones, and therefore opens a wide range of possible applications, it is clear that there is a need for determining structural requirements that need to be fulfilled to equip metal-organic crystals with mechanical flexibility. Recently, it was shown that cadmium(II) coordination polymers equipped with halopyrazine ligands adaptably respond to applied external stimuli, displaying elastic flexibility.[5] It was observed that introducing a slight structural changes, simply by exchanging bridging halide anion or halogen atom on halopyrazine ligand, changes the extent of elastic response significantly, while the quantification of their mechanical behaviour clearly showed that they can be categorized into three main subgroups, highly, moderately and slightly elastic. To get an invaluable insight into the phenomenon, we decided to systematically examine similar classes of coordination polymers by introducing slight structural differences through the exchange of supramolecular functionalities only. Herein we opted for pyridine-based ligands decorated with cyano functionality to explore their impact on macroscopic mechanical output. It was determined that the position of cyano group on pyridine ring, as well as used bridging halide anion, dictate the nature and extent of mechanical response. For crystals that displayed elastic behaviour, the responses were quantified and correlated with structural features, primarily the strength and geometry of supramolecular interactions, and compared with the mechanical behaviour of similar metal-containing systems.
The design of desired supramolecular architectures requires deep and clear understanding of supra... more The design of desired supramolecular architectures requires deep and clear understanding of supramolecular interactions and the fine balance between them. Hydrogen bond has already been extensively studied in this context, and many useful strategies for effective supramolecular synthesis based on this particular interaction have been reported. Halogen bond, on the other hand, has only recently been recognized as a useful structure- directing interaction, and several guidelines for selectivity of halogen-bonding interaction in the assembly process of organic solids have been suggested. The understanding of halogen- bonding interaction in molecular recognition processes of metal-containing systems are still at an early stage of development. Here we have prepared and structurally characterized a series of hexafluoroacetylacetonate (hfac) complexes of Co(II), Ni(II) and Cu(II) with 3-iodopyridine with idea to explore the selectivity of the halogen-bonding interaction in the metal- conta...
It has been shown that NO2···NO2 interactions are comparable in strength to weak hydrogen bonds a... more It has been shown that NO2···NO2 interactions are comparable in strength to weak hydrogen bonds and can have a structure determining role in assembling organic molecules that lack stronger halogen or hydrogen bond donors and acceptors. Nitro groups are often found in nitrogen rich energetic materials where they generally contribute to destabilization of the material resulting in its thermal, shock or mechanical instability. While it is highly unlikely that NO2···NO2 interactions will ever be used as a crystal engineering tool for the design of energetic materials, better understanding of these interactions could further unveil the correlation between structure and properties of energetic materials. We have prepared a series of hexafluoroacetylacetate complexes with 3- nitropyridine, e.g. the complexes of cobalt(II), nickel(II) and copper(II), to investigate the structure directing potential of NO2···NO2 interactions in assemblies of metal-organic systems in the absence of stronger h...
CrystEngComm, 2020
The crystal structures of six novel Ag+ complexes with NO3− and dihalopyridines revealed intrigui... more The crystal structures of six novel Ag+ complexes with NO3− and dihalopyridines revealed intriguing differences that were interpreted by DFT calculations.
Acta Crystallographica Section A Foundations and Advances, 2019
Research based on Margaret Etter's Rules [1] has shown that hydrogen and halogen bond donor-accep... more Research based on Margaret Etter's Rules [1] has shown that hydrogen and halogen bond donor-acceptor pairings follow a hierarchy based on their strengths which can be correlated with calculated molecular electrostatic potential (MEP) values. Studies conducted on organic systems have shown that it is possible to predict the donoracceptor pairing if the difference in MEP values is significant. It still remains to be determined if insights obtained for organic systems can be used in a tandem with metal centers. We have shown in our previous work that MEP values can be used to rationalize the supramolecular connectivity in the metal-organic setting for both hydrogen [2] and halogen [3] bonds. We have also shown that it is possible to use MEP values to predict the supramolecular connectivity in 2,4-pentanedionate (acac)-based complexes (Ni II , Co II , Cu II), equipped with the lactam moiety [4]. The goal of our current research is to determine if it is possible to use MEP values to predict the supramolecular connectivity in systems displaying more conformational freedom. To assess this hypothesis, we used acac-based complexes of Co(II) and Ni(II) with small heterocyclic ligands equipped with the amide functionality, and here we are reporting on the results.
Acta Crystallographica Section E Crystallographic Communications, 2020
A 6-chloronicotinate (6-Clnic) salt of a one-dimensional cationic nickel(II) coordination polymer... more A 6-chloronicotinate (6-Clnic) salt of a one-dimensional cationic nickel(II) coordination polymer with 4,4′-bipyridine (4,4′-bpy), namely, catena-poly[[[tetraaquanickel(II)]-μ-4,4′-bipyridine-κ2 N:N′] bis(6-chloronicotinate) tetrahydrate], {[Ni(C10H8N2)(H2O)4](C6H3ClNO2)2·4H2O} n or {[Ni(4,4′-bpy)(H2O)4](6-Clnic)2·4H2O} n , (1), was prepared by the reaction of nickel(II) sulfate heptahydrate, 6-chloronicotinic acid and 4,4′-bipyridine in a mixture of water and ethanol. The molecular structure of 1 comprises a one-dimensional polymeric {[Ni(4,4′-bpy)(H2O)4]2+} n cation, two 6-chloronicotinate anions and four water molecules of crystallization per repeating polymeric unit. The nickel(II) ion in the polymeric cation is octahedrally coordinated by four water molecule O atoms and by two 4,4′-bipyridine N atoms in the trans position. The 4,4′-bipyridine ligands act as bridges and, thus, connect the symmetry-related nickel(II) ions into an infinite one-dimensional polymeric chain extending...
Acta Crystallographica Section E Crystallographic Communications, 2020
A copper(II) dimer with the deprotonated anion of 2-bromonicotinic acid (2-BrnicH), namely, tetra... more A copper(II) dimer with the deprotonated anion of 2-bromonicotinic acid (2-BrnicH), namely, tetrakis(μ-2-bromonicotinato-κ2 O:O′)bis[aquacopper(II)](Cu—Cu), [Cu2(H2O)2(C6H3BrNO2)4] or [Cu2(H2O)2(2-Brnic)4], (1), was prepared by the reaction of copper(II) chloride dihydrate and 2-bromonicotinic acid in water. The copper(II) ion in 1 has a distorted square-pyramidal coordination environment, achieved by four carboxylate O atoms in the basal plane and the water molecule in the apical position. The pair of symmetry-related copper(II) ions are connected into a centrosymmetric paddle-wheel dinuclear cluster [Cu...Cu = 2.6470 (11) Å] via four O,O′-bridging 2-bromonicotinate ligands in the syn-syn coordination mode. In the extended structure of 1, the cluster molecules are assembled into an infinite two-dimensional hydrogen-bonded network lying parallel to the (001) plane via strong O—H...O and O—H...N hydrogen bonds, leading to the formation of various hydrogen-bond ring motifs: dimeric R ...
Crystal Growth & Design, 2019
A crystalline cadmium(II) coordination trimer with pyridine-4-propanamide (4-propy), [Cd 3 Cl 4 (... more A crystalline cadmium(II) coordination trimer with pyridine-4-propanamide (4-propy), [Cd 3 Cl 4 (H 2 O) 4 (4propy) 6 ](CH 3 CH 2 COO) 2 , readily responds to external stimuli while preserving crystal integrity. Two polymorphic forms, Polymorph-I (triclinic form) and Polymorph-II (monoclinic form), undergo a reversible single-crystal-tosingle-crystal conformational polymorph transformation upon temperature change, while the triclinic form (Polymorph-I) additionally shows substantial reversible sorption/desorption potential via two pathways, in response to stimulation by (i) elevated temperature, and (ii) reduced pressure. The elucidation of the conformational transformation via a variety of ex situ and in situ methods (SCXRD, VT-PXRD, TG/DSC and VT-IR), complemented by in-depth theoretical studies, suggested that the conformational transformation might be a process that occurs slowly and continuously over a wider temperature range, with different processes (distinctive conformational changes) taking place over different temperature intervals.
IUCrJ, 2018
In order to develop transferable and practical avenues for the assembly of coordination complexes... more In order to develop transferable and practical avenues for the assembly of coordination complexes into architectures with specific dimensionality, a strategy utilizing ligands capable of simultaneous metal coordination and self-complementary hydrogen bonding is presented. The three ligands used, 2(1H)-pyrazinone, 4(3H)-pyrimidinone and 4(3H)-quinazolinone, consistently deliver the required synthetic vectors in a series of CdII coordination polymers, allowing for reproducible supramolecular synthesis that is insensitive to the different steric and geometric demands from potentially disruptive counterions. In all nine crystallographically characterized compounds presented here, directional intermolecular N-H⋯O hydrogen bonds between ligands on adjacent complex building blocks drive the assembly and orientation of discrete building blocks into largely predictable topologies. Furthermore, whether the solids are prepared from solution or through liquid-assisted grinding, the structural o...
Acta Crystallographica Section A Foundations and Advances, 2016
Figure 1. Elastic bending in crystals of [CdBr 2 (I-pz) 2 ] n .
Acta Crystallographica Section A Foundations and Advances, 2015
Crystal Growth & Design, 2016
Acta Crystallographica Section A Foundations and Advances, 2015
Acta Crystallographica Section A Foundations and Advances, 2015
Crystal Growth & Design, 2016
Molecular electrostatic potential based guidelines for selectivity of halogen-bond interactions w... more Molecular electrostatic potential based guidelines for selectivity of halogen-bond interactions were explored via systematic co-crystallizations of 9 perfluorinated halogen-bond donors and 12 ditopic acceptors presenting two binding sites with different electrostatic potentials. A total of 89 of the 108 reactions resulted in co-crystal formation (as indicated by IR spectroscopy), and 35 new crystal structures were obtained. Methanol was exclusively used as a solvent for crystal growth in order to avoid any potential solvent−solute bias throughout these experiments. The structures were organized into three different groups depending upon the specific nature of the observed halogen-bond connectivities in each case. The electrostatic potential difference between the two acceptor sites on each molecule was defined as the ΔE value. Group 1 comprised acceptor molecules with a ΔE value below 35 kJ/mol units, and in this category halogen bonding took place on both binding sites in all co-crystals (9/9). Ditopic acceptor molecules in Group 2 were characterized by a ΔE value in the 35−65 kJ/mol range, and in this group half the structures showed halogen bonding to the best acceptor (11/22) and half the structures showed halogen bonding to both binding sites (11/22). In Group 3 the ΔE value was >167 kJ/mol, and in all of the co-crystals found herein (7/7), the halogen-bond donor favored the best acceptor site. These results allow us to propose some tentative guidelines and rationales for halogen-bond preferences in competitive systems. If ΔE < 35 kJ/mol, the electrostatic potential difference is not large enough to allow the donor molecules to form halogen bonds of sufficiently different thermodynamic strength to result in any pronounced molecular recognition preference (typically both, or several acceptors are then engaged in halogen bonding). Upon the basis of data produced in this study, in combination with relevant structures from the Cambridge Structural Database, it seems reasonable to suggest that if the ΔE value between two geometrically accessible halogen-bond acceptor sites is greater than 75 kJ/mol, the thermodynamic advantage of forming halogen bonds to the best acceptor provides a strong enough driving force that the best donor consistently interacts with the best acceptor; intermolecular selectivity is the result. However, if the ΔE resides between these two proposed boundaries, the outcome is unpredictable, and other factors are then likely to be responsible for the path that a particular supramolecular reaction will follow.