An Unprecedented Stimuli-Controlled Single-Crystal Reversible Phase Transition of a Metal-Organic Framework and Its Application to a Novel Method of Guest Encapsulation

Recent Advances in Carborane-Based Crystalline Porous Materials

The field of carborane research has witnessed continuous development, leading to the construction and development of a diverse range of crystalline porous materials for various applications. Moreover, innovative synthetic approaches are expanding in this field. Since the first report of carborane-based crystalline porous materials (CCPMs) in 2007, the synthesis of carborane ligands, particularly through innovative methods, has consistently posed a significant challenge in discovering new structures of CCPMs. This paper provides a comprehensive summary of recent advances in various synthetic approaches for CCPMs, along with their applications in different domains. The primary challenges and future opportunities are expected to stimulate further multidisciplinary development in the field of CCPMs.

Magnetic properties and magnetocaloric effect of Ln = Dy, Tb carborane-based metal-organic frameworks

We present the synthesis and magneto-thermal properties of carborane-based lanthanide metal-organic frameworks (MOFs) with the formula {[(Ln)3(mCB-L)4(NO3)(DMF)n]·Solv}, where Ln = Dy or Tb, characterized by dc and ac susceptibility, X-ray absorption spectroscopy (XAS), X-ray magnetic circular dichroism (XMCD) and heat capacity measurements. The MOF structure is formed by polymeric 1D chains of Ln ions with three different coordination environments (Ln1, Ln2, Ln3) running along the b-axis, linked by carborane-based linkers thus to provide a 3D structure. Static magnetic measurements reveal that these MOFs behave at low temperature as a system of S* = 1/2 Ising spins, weakly interacting ferromagnetically along the 1D polymeric chain (J*/kB = +0.45 K (+0.5 K) interaction constant estimated for Dy-MOF (Tb-MOF)) and coupled to Ln ions in adjacent chains through dipolar antiferromagnetic interactions. The Dy MOF exhibits slow relaxation of magnetization through a thermally activated process, transitioning to quantum tunneling of the magnetization at low temperatures, while both compounds exhibit field-induced relaxation through a very slow, direct process. The maximum magnetic entropy changes (-ΔSmaxm) for an applied magnetic field change of 2-0 T are 5.71 J kg-1 K-1 and 4.78 J kg-1 K-1, for Dy and Tb MOFs, respectively, while the magnetocaloric effect (MCE) peak for both occurs at T ∼ 1.6 K, approximately double that for the Gd counterpart.

Crystals of Ni6L12 Ellipsoidal Tubes as Single-Crystal-to-Single-Crystal Adsorption Matrix: Penetrative Study of Self-Assembled Crystals vs Guest-Exchanged Crystals

Informative similarities/differences between self-assembled and single-crystal-to-single-crystal (SCSC) guest-exchanged crystals based on both the molecular structure and adsorption nature are observed. The self-assembly of Ni(ClO4)2 with a dicyclopentyldi(pyridine-3-yl)silane bidentate ligand (L) in a mixture of toluene and acetonitrile gives rise to purple crystals consisting of double-stranded ellipsoidal tubes, [Ni6(ClO4)4(CH3CN)8L12]·8ClO4·4CH3CN·5C7H8. The coordinated acetonitriles as well as the solvates are removed at 170 °C to transform the purple crystals into blue crystals of [Ni(ClO4)2L2]n that return to the original crystals in the mixture of toluene and acetonitrile. Further, the toluene and acetonitrile solvates of the original crystals are replaced by o-, m-, and p-xylene isomers within 5 min in a SCSC manner. In the present study, SCSC xylene-exchanged crystals were compared with crystals obtained from direct self-assembly in a mixture of each xylene isomer and acetonitrile.

Supramolecular Architectures Bearing Half-Sandwich Iridium- or Rhodium-Based Carboranes: Design, Synthesis, and Applications

The utilization of carboranes in supramolecular chemistry has attracted considerable attention. The unique spatial configuration and weak interaction forces of carboranes can help to explore the properties of supramolecular complexes, particularly via host-guest chemistry. Additionally, certain difficulties encountered in carborane development─such as controlled B-H bond activation─can be overcome by judiciously selecting metal centers and their adjacent ligands. However, few studies are being conducted in this nascent research area. With advances in this field, novel carborane-based supramolecular complexes will likely be prepared, structurally characterized, and intrinsically investigated. To expedite these efforts, we present major findings from recent studies, including π-π interactions, host-guest associations, and steric effects, which have been leveraged to implement a regioselective process for activating B(2,9)-, B(2,8)-, and B(2,7)-H bonds of para-carboranes and B(4,7)-H bonds of ortho-carboranes. Future studies should clarify the unique weak interactions of carboranes and their potential for enhancing the utility of supramolecular complexes. Although carboranes exhibit several unique weak interactions (such as dihydrogen-bond [Bδ+-Hδ-···Hδ+-Cδ-], Bδ+-Hδ-···M+, and Bδ+-Hδ-···π interactions), the manner in which they can be utilized remains unclear. Supramolecular complexes, particularly those based on host-guest chemistry, can be utilized as a platform for demonstrating potential applications of these weak interactions. Owing to the importance of alkane separation, applications related to the recognition and separation of alkane isomers via dihydrogen-bond interactions are primarily summarized. Advances in the research of unique weak interactions in carboranes will certainly lead to more possibilities for supramolecular chemistry.

A Theoretical Perspective to Decipher the Origin of High Hydrogen Storage Capacity in Mn(II) Metal-Organic Framework

Herein, we report a detailed periodic DFT investigation of Mn(II)-based [(Mn₄ Cl)₃ (BTT)₈ ]^3- (BTT^3- =1,3,5-benzenetristetrazolate) metal-organic framework (MOF) to explore various hydrogen binding pockets, nature of MOF…H₂ interactions, magnetic coupling and, H₂ uptake capacity. Earlier experiments found an uptake capacity of 6.9 wt % of H_2, with the heat of adsorption estimated to be ∼10 kJ/mol, which is one among the highest for any MOFs reported. Our calculations unveil different binding sites with computed binding energy varying from -6 to -15 kJ/mol. The binding of H₂ at the Mn²⁺ site is found to be the strongest (site I), with H₂ found to bind Mn²⁺ ion in a η² fashion with a distance of 2.27 Å and binding energy of -15.4 kJ/mol. The bonding analysis performed using NBO and AIM reveal a strong donation of σ (H₂ ) to the d_z ² orbital of the Mn²⁺ ion responsible for such large binding energy. The other binding pockets, such as -Cl (site II) and BTT ligands (site III and IV) were found to be weaker, with the binding energy decreasing in the order I>II>III>IV. The average binding energy computed for these four sites put together is 9.6 kJ/mol, which is in excellent agreement with the experimental value of ∼10 kJ/mol. We have expanded our calculations to compute binding energy for multiple sites simultaneously, and in this model, the binding energy per site was found to decrease as we increased the number of H₂ molecules suggesting electronic and steric factors controlling the overall uptake capacity. The calculated adsorption isotherm using the GCMC method reproduces the experimental observations. Further, the magnetic coupling computed for the unbound MOF reveals moderate ferromagnetic and strong antiferromagnetic coupling within the tetrameric {Mn₄ } unit leading to a three-up-one-down spin configuration as the ground state. These were then coupled ferromagnetically to other tetrameric units in the MOF network. The magnetic coupling was found to alter only marginally upon gas binding, suggesting that both exchange interaction and the spin-states are unlikely to play a role in the H₂ uptake. This is contrary to the O₂ uptake studied lately, where strong dependence on exchange-coupling/spin state was witnessed, suggesting exchange-coupling/magnetic field dependent binding as a viable route for gas separation.

Adsorptive Separation of CO2 by a Hydrophobic Carborane-Based Metal-Organic Framework under Humid Conditions

We report that the carborane-based metal-organic framework (MOF) mCB-MOF-1 can achieve high adsorptive selectivity for CO₂:N₂ mixtures. This hydrophobic MOF presenting open metal sites shows high CO₂ adsorption capacity and remarkable selectivity values that are maintained even under extremely humid conditions. The comparison of mCB-MOF-1' with MOF-74(Ni) demonstrates the superior performance of the former under challenging moisture operation conditions.

Understanding the Structural Collapse during Activation of Metal-Organic Frameworks with Copper Paddlewheels

Many metal-organic frameworks (MOFs) suffer from stability issues as they can be easily amorphized from various external stimuli. In particular, it is common to observe structural collapse during the activation process of removing the synthesis solvent. In this study, we conduct high-throughput computational analysis that focuses on the activation status of MOFs that possess copper paddlewheel metal nodes. From the analysis, various mechanical properties (e.g., bulk, Young's, and shear moduli) were found to be good predictors for collapse. Furthermore, we have identified anomaly MOFs with good mechanical stability that were previously reported to collapse. Accordingly, the activation process was reattempted with improved techniques, and one of these MOFs was successfully activated.

Water-Stable Carborane-Based Eu3+/Tb3+ Metal-Organic Frameworks for Tunable Time-Dependent Emission Color and Their Application in Anticounterfeiting Bar-Coding

Luminescent lanthanide metal-organic frameworks (Ln-MOFs) have been shown to exhibit relevant optical properties of interest for practical applications, though their implementation still remains a challenge. To be suitable for practical applications, Ln-MOFs must be not only water stable but also printable, easy to prepare, and produced in high yields. Herein, we design and synthesize a series of m CB-Eu _y Tb _1-y (y = 0-1) MOFs using a highly hydrophobic ligand mCBL1: 1,7-di(4-carboxyphenyl)-1,7-dicarba-closo-dodecaborane. The new materials are stable in water and at high temperature. Tunable emission from green to red, energy transfer (ET) from Tb³⁺ to Eu³⁺, and time-dependent emission of the series of mixed-metal m CB-Eu _y Tb _1-y MOFs are reported. An outstanding increase in the quantum yield (QY) of 239% of mCB-Eu (20.5%) in the mixed mCB-Eu_0.1Tb_0.9 (69.2%) is achieved, along with an increased and tunable lifetime luminescence (from about 0.5 to 10 000 μs), all of these promoted by a highly effective ET process. The observed time-dependent emission (and color), in addition to the high QY, provides a simple method for designing high-security anticounterfeiting materials. We report a convenient method to prepare mixed-metal Eu/Tb coordination polymers (CPs) that are printable from water inks for potential applications, among which anticounterfeiting and bar-coding have been selected as a proof-of-concept.

Enhancement of Output Performance of Triboelectric Nanogenerator by Switchable Stimuli in Metal-Organic Frameworks for Photocatalysis

Precise control of the structure of crystalline materials is an efficient strategy to manipulate the fundamental performance of solids. In metal-organic framework (MOF) materials, this control can be realized by reversible cation-exchange through chemically driven changes in the crystalline state. Herein, we reported that the reversible structural transformations between an anionic Zn-MOF (1) and a topologically equivalent bimetallic Zn/Co-MOF (2) were accomplished. Both MOFs powders and their hybrid composites were used as positive electrode materials to assemble triboelectric nanogenerators (TENGs). The results demonstrated that the output performance of the Zn/Co-MOF-TENG was effectively improved because the introduction of Co ions makes electron transfer easier. Moreover, the output performance of the TENGs based on MOF@PVDF (PVDF = polyvinylidene fluoride) composite films showed that the Zn/Co-MOF@PVDF-TENG possessed much higher output than these corresponding film-based and MOF-based TENGs. As a practical application, the superior output of Zn/Co-MOF@PVDF-TENG was used to light an ultraviolet lamp plate for the [2 + 2] photochemical cycloaddition of organometallic macrocycles.

N-Aminoacyl-3-amino-nido-carboranes as a Group of Boron-Containing Derivatives of Natural Amino Acids

A new group of nido-carboranyl derivatives of natural (S)-amino acids containing from 9 to 18 boron atoms was obtained in good yields as a result of acylation of 3-amino-1,2-dicarba-closo-dodecaborane followed by deboronation. The proposed approach is convenient and based on the use of readily available reagents and is suitable for the synthesis of enantiopure nido-carboranyl derivatives of amino acids with various side chains, including water-soluble boron-containing amino acids (17 examples).

Orientational isomerisation of guest molecules in equilibrium in a tubular host crystal formed via halogen and hydrogen bonding

Fine-tuning of the ratio of two different states is important in controlling the structures and functions of crystalline materials. Here we report that clathrated guest molecules inside a tubular host...

Synthesis and structural properties of a 2D Zn(II) dodecahydroxy-closo-dodecaborate coordination polymer

In this work, we discuss the synthesis and characterization of a 2D coordination polymer composed of a dianionic perhydroxylated boron cluster, [B12(OH)12]2-, coordinated to Zn(II)—the first example of a transition...

Rational design of carborane-based Cu2-paddle wheel coordination polymers for increased hydrolytic stability

A new unsymmetric carborane-based dicarboxylic linker provided a 1D Cu₂-paddle wheel coordination polymer (2) with much higher hydrolytic stability than the corresponding 2D Cu₂-paddle wheel polymer (1), obtained from a related more symmetrical carborane-based linker. Both 1 and 2 were used as efficient heterogeneous catalysts for a model aza-Michael reaction but only 2 can be reused several times without significant degradation in catalytic activity.

Diblock copolymers directing construction of hierarchically porous metal-organic frameworks for enhanced-performance supercapacitors

A rationally designed strategy is developed to synthesize hierarchically porous Fe-based metal-organic frameworks (P-Fe-MOF) via solution-based self-assembly of diblock copolymers. The well-chosen amphiphilic diblock copolymers (BCP) of polystyrene-block-poly(acrylic acid) (PS-b-PAA) exhibits outstanding tolerance capability of rigorous conditions (e.g. strong acidity or basicity, high temperature and pressure), steering the peripheral crystallization of Fe-based MOF by anchoring ferric ions with outer PAA block. Importantly, the introduction of BCP endows MOF materials with additional mesopores (∼40 nm) penetrating whole crystals, along with their inherent micropores and introduced macropores. The unique hierarchically porous architecture contributes to fast charge transport and electrolyte ion diffusion, and thus promotes their redox reaction kinetics processes. Accordingly, the resultant P-Fe-MOF material as a new electrode material for supercapacitors delivers the unprecedented highest specific capacitance up to 78.3 mAh g^-1 at a current density of 1 A g^-1, which is 9.8 times than that of Fe-based MOF/carbon nanotubes composite electrode reported previously. This study may inspire new design of porous metal coordination polymers and advanced electrode materials for energy storage and conversion field.

Linker Expansion and Its Impact on Switchability in Pillared-Layer MOFs

Linker elongation is an important method to systematically adjust porosity and pore size in isoreticular MOFs. In flexible structures, this approach opens the possibility for the systematic analysis of the building blocks and their contribution to the overall flexible behavior enabling tuning of the framework responsivity toward molecular stimuli. In this work, we report two new compounds isoreticular to the highly flexible pillared layer structure DUT-8(Ni) ([Ni₂(2,6-ndc)₂(dabco)]_n, 2,6-ndc = 2,6-naphthalenedicarboxylate, dabco = 1,4-diazabicylo[2.2.2]octane). Aromatic linker 2,6-ndc was substituted by longer carboxylic linkers, namely, 4,4'-biphenyldicarboxylate (4,4'-bpdc) and 4,4'-stilbenedicarboxylate (4,4'-sdc), while the dabco pillar was retained. The structural response of the new compounds toward the desolvation and adsorption of various fluids was studied using advanced in situ PXRD techniques, demonstrating distinct differences in the flexible behavior of three compounds and disclosing the impact of linker structure on the framework response. Theoretical calculations provide mechanistic insights and an energetic rationale for the pronounced differences in switchability observed. The energetics of linker bending and linker-linker dispersion interactions govern the phase transitions in investigated MOFs.

Post-synthetic modification of a highly flexible 3D soft porous metal–organic framework by incorporating conducting polypyrrole: enhanced MOF stability and capacitance as an electrode material

Porous, stable and functional MOF polymer hybrids can be prepared by the in situ polymerization of otherwise unstable soft crystals.

Destruction of Metal-Organic Frameworks: Positive and Negative Aspects of Stability and Lability

Metal-organic frameworks (MOFs), constructed from organic linkers and inorganic building blocks, are well-known for their high crystallinity, high surface areas, and high component tunability. The stability of MOFs is a key prerequisite for their potential practical applications in areas including storage, separation, catalysis, and biomedicine since it is essential to guarantee the framework integrity during utilization. However, MOFs are prone to destruction under external stimuli, considerably hampering their commercialization. In this Review, we provide an overview of the situations where MOFs undergo destruction due to external stimuli such as chemical, thermal, photolytic, radiolytic, electronic, and mechanical factors and offer guidelines to avoid unwanted degradation happened to the framework. Furthermore, we discuss possible destruction mechanisms and their varying derived products. In particular, we highlight cases that utilize MOF instability to fabricate varying materials including hierarchically porous MOFs, monolayer MOF nanosheets, amorphous MOF liquids and glasses, polymers, metal nanoparticles, metal carbide nanoparticles, and carbon materials. Finally, we provide a perspective on the utilization of MOF destruction to develop advanced materials with a superior hierarchy for various applications.

Reversible Phase Transition of Porous Coordination Polymers

Porous coordination polymers or metal-organic frameworks with reversible phase-transition behavior possess some attractive properties, and can respond to external stimuli, including physical and chemical stimuli, in a dynamic fashion. Their phase transitions can be triggered by adsorption/desorption of guest molecules, temperature changes, high pressure, light irradiation, and electric fields; these mainly include two types of transitions: crystal-amorphous and crystal-crystal transitions. These types of porous coordination polymers have received much attention because of their interesting properties and potential applications. Herein, reversible phase transition porous coordination polymers are summarized and classified based on different stimuli sources. Corresponding typical examples are then introduced. Finally, examples of their applications in gas separation, chemical sensors, guest molecule encapsulation, and energy storage are also presented.

3-(4-Methylthiophenyl)acetylacetone – ups and downs of flexibility in the synthesis of mixed metal–organic frameworks. Ditopic bridging of hard and soft cations and site-specific desolvation

Different Pearson-hardness of O and S donors leads to well-ordered mixed metal–organic frameworks.

Reversible Polymorphic Transition and Hysteresis-Driven Phase Selectivity in Single-Crystalline C8-BTBT Rods

Organic semiconductors (OSCs) are highly susceptible to the formation of metastable polymorphs that are often transformed by external stimuli. However, thermally reversible transformations in OSCs with stability have not been achieved due to weak van der Waals forces, and poor phase homogeneity and crystallinity. Here, a polymorph of a single crystalline 2,7-dioctyl[1] benzothieno[3,2-b][1]benzothio-phene rod on a low molecular weight poly(methyl methacrylate) (≈120k) that limits crystal coarsening during solvent vapor annealing is fabricated. Molecules in the polymorph lie down slightly toward the substrate compared to the equilibrium state, inducing an order of greater resistivity. During thermal cycling, the polymorph exhibits a reversible change in resistivity by 5.5 orders with hysteresis; this transition is stable toward bias and thermal cycling. Remarkably, varying cycling temperatures leads to diverse resistivities near room temperature, important for nonvolatile multivalue memories. These trends persist in the carrier mobility and on/off ratio of the polymorph field-effect transistor. A combination of in situ grazing incident wide angle X-ray scattering analyses, visualization for electronic and structural analysis simulations, and density functional theory calculations reveals that molecular tilt governs the charge transport characteristics; the polymorph transforms as molecules tilt, and thereby, only a homogeneous single-crystalline phase appears at each temperature.

Functionalized Dynamic Metal-Organic Frameworks as Smart Switches for Sensing and Adsorption Applications

Over the past two decades, metal-organic frameworks (MOFs) with flexible structures or dynamic behavior have shown great potential as functional materials in many fields. This paper presents a review of these dynamic and functional MOFs, which can undergo controllable and reversible transformation, with regard to their application as smart switches. Trigger conditions, which include physical/chemical stimuli (e.g., guest molecules, light, temperature, pressure), are also discussed. Research methods for investigating the dynamic processes and mechanisms involving experimental characterization and computational modeling are briefly mentioned as well. The emphasis is on the aspects of the design and functionalization of dynamic MOFs. The pre-design of metal nodes, organic linkers, and topology, as well as post-modification of components, increases the possibility of obtaining functionalized dynamic materials. Recent advances with regard to potential applications for dynamic frameworks as smart switches for adsorption and sensing are also reviewed.

Metal-Organic Frameworks in Modern Physics: Highlights and Perspectives

Owing to the synergistic combination of a hybrid organic-inorganic nature and a chemically active porous structure, metal-organic frameworks have emerged as a new class of crystalline materials. The current trend in the chemical industry is to utilize such crystals as flexible hosting elements for applications as diverse as gas and energy storage, filtration, catalysis, and sensing. From the physical point of view, metal-organic frameworks are considered molecular crystals with hierarchical structures providing the structure-related physical properties crucial for future applications of energy transfer, data processing and storage, high-energy physics, and light manipulation. Here, the perspectives of metal-organic frameworks as a new family of functional materials in modern physics are discussed: from porous metals and superconductors, topological insulators, and classical and quantum memory elements, to optical superstructures, materials for particle physics, and even molecular scale mechanical metamaterials. Based on complementary properties of crystallinity, softness, organic-inorganic nature, and complex hierarchy, a description of how such artificial materials have extended their impact on applied physics to become the mainstream in material science is offered.

A Reversible Phase Transition of 2D Coordination Layers by B-H∙∙∙Cu(II) Interactions in a Coordination Polymer

Materials that combine flexibility and open metal sites are crucial for myriad applications. In this article, we report a 2D coordination polymer (CP) assembled from CuII ions and a flexible meta-carborane-based linker [Cu₂(L1)₂(Solv)₂]•xSolv (1-DMA, 1-DMF, and 1-MeOH; L1: 1,7-di(4-carboxyphenyl)-1,7-dicarba-closo-dodecaborane). 1-DMF undergoes an unusual example of reversible phase transition on solvent treatment (i.e., MeOH and CH₂Cl₂). Solvent exchange, followed by thermal activation provided a new porous phase that exhibits an estimated Brunauer-Emmett-Teller (BET) surface area of 301 m² g^-1 and is capable of a CO₂ uptake of 41 cm³ g^-1. The transformation is reversible and 1-DMF is reformed on addition of DMF to the porous phase. We provide evidence for the reversible process being the result of the formation/cleavage of weak but attractive B-H∙∙∙Cu interactions by a combination of single-crystal (SCXRD), powder (PXRD) X-ray diffraction, Raman spectroscopy, and DFT calculations.

A Microporous Metal-Organic Framework Supramolecularly Assembled from a CuII Dodecaborate Cluster Complex for Selective Gas Separation

A novel 3D metal-organic framework BSF-1 based on the closo-dodecaborate cluster [B₁₂ H₁₂ ]^2- was readily prepared at room temperature by supramolecular assembly of CuB₁₂ H₁₂ and 1,2-bis(4-pyridyl)acetylene. The permanent microporous structure was studied by X-ray crystallography, powder X-ray diffraction, IR spectroscopy, thermogravimetric analysis, and gas sorption. The experimental and theoretical study of the gas sorption behavior of BSF-1 for N₂ , C₂ H₂ , C₂ H₄ , CO₂ , C₃ H₈ , C₂ H₆ , and CH₄ indicated excellent separation selectivities for C₃ H₈ /CH₄ , C₂ H₆ /CH₄ , and C₂ H₂ /CH₄ as well as moderately high separation selectivities for C₂ H₂ /C₂ H₄ , C₂ H₂ /CO₂ , and CO₂ /CH₄ . Moreover, the practical separation performance of C₃ H₈ /CH₄ and C₂ H₆ /CH₄ was confirmed by dynamic breakthrough experiments. The good cyclability and high water/thermal stability render it suitable for real industrial applications.

All inorganic coordination polymers have been made possible with the m-carboranylphosphinate ligand

New examples of 1D coordination polymers (CPs) and complexes containing the purely inorganic carboranylphosphinate ligand [1-OPH(O)-1,7-closo-C2B10H11]- are reported. The reaction of Na[1-OPH(O)-1,7-closo-C2B10H11] salt with MCl2 (M = Mn, Co, Ni, Cu, Zn and Cd) in MeOH or EtOH leads to compounds 1-8. All compounds have been exhaustively characterized by analytical and spectroscopic techniques. X-ray analysis and spectroscopy characterization revealed the differences between the isolated compounds: 1D polymeric chains (CPs) with carboranylphosphinate ligand bridges have been obtained with MnII, CdII or ZnII centres, whereas compounds with low nuclearity have been isolated with CuII, CoII and NiII. No polymeric structures were obtained in the CoII and NiII complexes due to the higher affinity of these metals for water than that for the m-carboranylphosphinate and accordingly, these complexes generate supramolecular hydrophobic/hydrophilic structures. The reactivity of manganese polymer 1 with water leads to the breakage of the polymer with the formation of a new mononuclear compound 2, and that in methanol leads back to the initial polymer 1. However, the reactivity of polymer 1 with 2,2'-bpy maintains the core present in the initial polymer, leading to the CP 3, which in methanol/water medium produces species of lower nuclearity. The magnetic properties of the compounds studied show weak antiferromagnetic coupling.