Versatile Tailoring of Paddle‐Wheel ZnII Metal–Organic Frameworks through Single‐Crystal‐to‐Single‐Crystal Transformations

A new tetracarboxylate ligand having short and long arms formed 2D layer Zn^II coordination polymer 1 with paddle‐wheel secondary building units under solvothermal conditions. The framework undergoes solvent‐specific single crystal‐to‐single crystal (SC‐SC) transmetalation to produce 1_Cu . With a sterically encumbered dipyridyl linker, the same ligand forms non‐interpenetrated, 3D, pillared‐layer Zn^II metal–organic framework (MOF) 2 , which takes part in SC‐SC linker‐exchange reactions to produce three daughter frameworks. The parent MOF 2 shows preferential incorporation of the longest linker in competitive linker‐exchange experiments. All the 3D MOFs undergo complete SC‐SC transmetalation with Cu^II, whereby metal exchange in different solvents and monitoring of X‐ray structures revealed that bulky solvated metal ions lead to ordering of the shortest linker in the framework, which confirms that the solvated metal ions enter through the pores along the linker axis.     

Single‐Crystal to Single‐Crystal Linker Substitution,Linker Place Exchange,and Transmetalation Reactions in Interpenetrated Pillared–Bilayer Zinc(II) Metal–Organic Frameworks

A twofold interpenetrated pillared–bilayer framework, {[Zn₃( L )₂( L₂ )(DMF)] ? (18DMF)(6H₂O)}_n ( 1 ), has been synthesized from the ligands tris(4′‐carboxybiphenyl)amine ( H₃L ) and 1,2‐bis(4‐pyridyl)ethylene ( L₂ ). The structure contains [Zn₃(COO)₆] secondary building units (SBUs), in which three Zn^II ions are almost linear with carboxylate bridging. This framework undergoes reversible pillar linker substitution reactions at the terminal Zn^II centers with three different dipyridyl linkers of different lengths to afford three daughter frameworks, 2 – 4 . Frameworks 2 – 4 are interconvertible through reversible linker substitution reactions. Also, competitive linker‐exchange experiments show preferential incorporation of linker L₃ in the parent framework 1 . The larger linker L₅ does not undergo such substitution reactions and framework 5 , which contains this linker, can be synthesized solvothermally as a twofold interpenetrated structure. Interestingly, when framework 5 is dipped in a solution of L₃ in DMF, linker substitution takes place as before, but linker L₅ now moves and diagonally binds two Zn^II centers to afford 6 as a nonpenetrated single framework. This linker place exchange reaction is unprecedented. All of these reactions take place in a single‐crystal to single‐crystal (SC‐SC) manner, and have been observed directly through X‐ray crystallography. In addition, each 3D framework undergoes complete copper(II) transmetalation.     

Unprecedented Second‐Timescale Blue/Green Emissions and Iodine‐Uptake‐Induced Single‐Crystal‐to‐Single‐Crystal Transformation in ZnII/CdII Metal–Organic Frameworks

The long‐persistent phosphorescent metal–organic framework (MOF) is a kind of highly desirable but rare material. Here, two new molecular MOF materials, {[Zn(tipa)Cl] ? NO₃ ? 2 DMF}_n ( 1 ) and {[Cd₂(tipa)₂Cl₄] ? 6 DMF}_n ( 2 ) (tipa=tri(4‐imidazolylphenyl)amine), which have 3D twofold interpenetrated ( utp ) and 2D noninterpenetrated ( kgd ) topologies, respectively, are reported. They exhibit unexpected long‐persistent emissions yet reported: At 77 K, they persist in glowing after stopping the UV irradiation on a timescale up to seconds at 77 K, which can be detected by the naked eye (ca. 2 s). Compounds 1 and 2 also undergo single‐crystal‐to‐single‐crystal (SC‐SC) transformations through different routes; a simple anion‐exchange route for 1 and a complicated replacement of μ₁‐Cl^? ions by DMF molecules accompanying I₃^? captured in the void for 2 .     

Breathing Effect in a Cobalt Phosphonate upon Dehydration/Rehydration: A Single‐Crystal‐to‐Single‐Crystal Study

Two cobalt phosphonates, [Co₂(2,2′‐bpy)₂(H₂O)(pbtcH)] ( 1 ) and [Co₂(H₂O)(pbtcH)(phen)₂] ( 2 ; pbtcH₅=5‐phosphonatophenyl‐1,2,4‐tricarboxylic acid, 2,2′‐bpy=2,2′‐bipyridine, phen=1,10‐phenanthroline), with layer structures are reported. Compound 1 contains O‐C‐O and O‐P‐O bridged tetramers of Co₄, which are further connected by pbtcH^4? units to form a layer. In compound 2 , the cobalt tetramers made up of water‐bridged Co₂ dimers and O‐P‐O linkages are connected into a layer by pbtcH^4? units. Upon dehydration, compounds 1 and 2 experience single‐crystal‐to‐single‐crystal (SC–SC) structural transformations to form [Co₂(2,2′‐bpy)₂(pbtcH)] ( 1 a ) and [Co₂(pbtcH)(phen)₂] ( 2 a ), respectively. The process is reversible in each case. Notably, a breathing effect is observed for 1 , accompanied by pore opening and closing due to the reorientation of the coordinated 2,2′‐bpy molecules. The transformation was also monitored by in situ IR measurements. Magnetic studies reveal that antiferromagnetic interactions are mediated between the magnetic centers in compounds 1 and 1 a , whereas ferromagnetic interactions are dominant in compound 2 .     

Two Robust Porous Metal–Organic Frameworks Sustained by Distinct Catenation: Selective Gas Sorption and Single‐Crystal‐to‐Single‐Crystal Guest Exchange

Assembly of copper(I) halide with a new tripodal ligand, benzene‐1,3,5‐triyl triisonicotinate (BTTP4), afforded two porous metal–organic frameworks, [Cu₂I₂(BTTP4)]?2 CH₃CN ( 1? 2 CH₃CN) and [CuBr(BTTP4)]?(CH₃CN ? CHCl₃ ? H₂O) ( 2? solvents), which have been characterized by IR spectroscopy, thermogravimetry (TG), single‐crystal, and powder X‐ray diffraction (PXRD) methods. Compound 1.CH3CN is a polycatenated 3D framework that consists of 2D (6,3) networks through inclined catenation, whereas 2 is a doubly interpenetrated 3D framework possessing the ThSi₂‐type ( ths ) (10,3)‐b topology. Both frameworks contain 1D channels of effective sizes 9×12 and 10×10 Ų, which amounts to 43 and 40 % space volume accessible for solvent molecules, respectively. The TG and variable‐temperature PXRD studies indicated that the frameworks can be completely evacuated while retaining the permanent porosity, which was further verified by measurement of the desolvated complex [Cu₂I₂(BTTP4)] ( 1′ ). The subsequent guest‐exchange study on the solvent‐free framework revealed that various solvent molecules can be adsorbed through a single‐crystal‐to‐single‐crystal manner, thus giving rise to the guest‐captured structures [Cu₂I₂(BTTP4)]?C₆H₆ ( 1.benzene ), [Cu₂I₂(BTTP4)]?2 C₇H₈ ( 1.2toluene ), and [Cu₂I₂(BTTP4)]?2 C₈H₁₀ ( 1.2ethyl benzene ). The gas‐adsorption investigation disclosed that two kinds of frameworks exhibited comparable CO₂ storage capacity (86–111 mL g^?1 at 1 atm) but nearly none for N₂ and H₂, thereby implying its separation ability of CO₂ over N₂ and H₂. The vapor‐adsorption study revealed the preferential inclusion of aromatic guests over nonaromatic solvents by the empty framework, which is indicative of selectivity toward benzene over cyclohexane.     

Post‐Synthetic Reversible Incorporation of Organic Linkers into Porous Metal–Organic Frameworks through Single‐Crystal‐to‐Single‐Crystal Transformations and Modification of Gas‐Sorption Properties

The porous metal–organic framework (MOF) {[Zn₂(TCPBDA)(H₂O)₂]?30 DMF?6 H₂O}_n ( SNU‐30 ; DMF=N,N‐dimethylformamide) has been prepared by the solvothermal reaction of N,N,N′,N′‐tetrakis(4‐carboxyphenyl)biphenyl‐4,4′‐diamine (H₄TCPBDA) and Zn(NO₃)₂?6 H₂O in DMF/tBuOH. The post‐synthetic modification of SNU‐30 by the insertion of 3,6‐di(4‐pyridyl)‐1,2,4,5‐tetrazine (bpta) affords single‐crystalline {[Zn₂(TCPBDA)(bpta)]?23 DMF?4 H₂O}_n ( SNU‐31 SC ), in which channels are divided by the bpta linkers. Interestingly, unlike its pristine form, the bridging bpta ligand in the MOF is bent due to steric constraints. SNU‐31 can be also prepared through a one‐pot solvothermal synthesis from Zn^II, TCPBDA^4?, and bpta. The bpta linker can be liberated from this MOF by immersion in N,N‐diethylformamide (DEF) to afford the single‐crystalline SNU‐30 SC , which is structurally similar to SNU‐30 . This phenomenon of reversible insertion and removal of the bridging ligand while preserving the single crystallinity is unprecedented in MOFs. Desolvated solid SNU‐30′ adsorbs N₂, O₂, H₂, CO₂, and CH₄ gases, whereas desolvated SNU‐31′ exhibits selective adsorption of CO₂ over N₂, O₂, H₂, and CH₄, thus demonstrating that the gas adsorption properties of MOF can be modified by post‐synthetic insertion/removal of a bridging ligand.     

A 3D Hybrid Praseodymium–Antimony–Oxochloride Compound: Single‐Crystal‐to‐Single‐Crystal Transformation and Photocatalytic Properties

A 3D organic–inorganic hybrid compound, (2‐MepyH)₃ [{Fe(1,10‐phen)₃}₃][{Pr₄Sb₁₂O₁₈(OH) Cl_11.5}(TDC)_4.5({Pr₄Sb₁₂O₁₈(OH)Cl_9.5} Cl)] ? 3 (2‐Mepy) ? 28 H₂O ( 1 ; 2‐Mepy=2‐methylpyridine, 1,10‐phen=1,10‐phenanthroline, H₂TDC=thiophene‐2,5‐dicarboxylic acid), was hydrothermally synthesized and structurally characterized. Unusually, two kinds of high‐nuclearity clusters, namely [(Pr₄Sb₁₂O₁₈ (OH)Cl₁₁)(COO)₅]^5? and [(Pr₄Sb₁₂O₁₈ (OH)Cl₉)Cl(COO)₅]^4?, coexist in the structure of compound 1 ; two of the latter clusters are doubly bridged by two μ₂‐Cl^? moieties to form a new centrosymmetric dimeric cluster. An unprecedented spontaneous and reversible single‐crystal‐to‐single‐crystal transformation was observed, which simultaneously involved a notable organic‐ligand movement between the metal ions and an alteration of the bridging ion in the dimeric cluster, induced by guest‐release/re‐adsorption, thereby giving rise to the interconversion between compound 1 and the compound (2‐MepyH)₃[{Fe(1,10‐phen)₃}₃][{Pr₄Sb₁₂O₁₈(OH)Cl_11.5}(TDC)₄({Pr₄Sb₁₂O₁₈Cl_10.5(TDC)_0.5(H₂O)_1.5}O_0.5)] ? 25 H₂O ( 1′ ). The mechanism of this transformation has also been discussed in great detail. Photocatalytic H₂‐evolution activity was observed for compound 1′ under UV light with Pt as a co‐catalyst and MeOH as a sacrificial electron donor.     

Postsynthetic Improvement of the Physical Properties in a Metal–Organic Framework through a Single Crystal to Single Crystal Transmetallation

A single crystal to single crystal transmetallation process takes place in the three‐dimensional (3D) metal–organic framework (MOF) of formula Mg^II₂{Mg^II₄[Cu^II₂(Me₃mpba)₂]₃}?45 H₂O ( 1 ; Me₃mpba^4?=N,N′‐2,4,6‐trimethyl‐1,3‐phenylenebis(oxamate)). After complete replacement of the Mg^II ions within the coordination network and those hosted in the channels by either Co^II or Ni^II ions, 1 is transmetallated to yield two novel MOFs of formulae Co₂^II{Co^II₄[Cu^II₂(Me₃mpba)₂]₃}?56 H₂O ( 2 ) and Ni₂^II{Ni^II₄[Cu^II₂(Me₃mpba)₂]₃}? 54 H₂O ( 3 ). This unique postsynthetic metal substitution affords materials with higher structural stability leading to enhanced gas sorption and magnetic properties.     

One‐Pot Tandem Photoredox and Cross‐Coupling Catalysis with a Single Palladium Carbodicarbene Complex

The combination of conventional transition‐metal‐catalyzed coupling (2 e^? process) and photoredox catalysis (1 e^? process) has emerged as a powerful approach to catalyze difficult cross‐coupling reactions under mild reaction conditions. Reported is a palladium carbodicarbene (CDC) complex that mediates both a Suzuki–Miyaura coupling and photoredox catalysis for C?N bond formation upon visible‐light irradiation. These two catalytic pathways can be combined to promote both conventional transition‐metal‐catalyzed coupling and photoredox catalysis to mediate C?H arylation under ambient conditions with a single catalyst in an efficient one‐pot process.     

Metal‐Ion Metathesis and Properties of Triarylboron‐Functionalized Metal–Organic Frameworks

An anionic metal–organic framework, H₃[(Mn₄Cl)₃ L ₈]?30 H₂O?2.5 DMF?5 Diox ( UPC‐15 ), was successfully prepared by the reaction of MnCl₂ with tris(p‐carboxylic acid)tridurylborane (H₃ L ) under solvothermal conditions. UPC‐15 with wide‐open pores (～18.8 Å) is constructed by packing of octahedral and cuboctahedral cages, and exhibits high gas‐sorption capabilities. Notably, UPC‐15 shows selective adsorption of cationic dyes due to the anion framework. Moreover, the catalytic and magnetic properties were investigated, and UPC‐15 can highly catalyze the cyanosilylation of aromatic aldehydes. UPC‐15 exhibits the exchange of metal ions from Mn to Cu in a single‐crystal‐to‐single‐crystal manner to generate UPC‐16 , which could not be obtained by the direct solvothermal reaction of CuCl₂ and H₃ L. UPC‐16 exhibits similar properties for gas sorption, dye separation, and catalytic activity. However, the magnetic behaviors for UPC‐15 and UPC‐16 are distinct due to the metal‐specific properties. Below 47 K, UPC‐15 exhibits a ferromagnetic coupling but UPC‐16 shows a dominant antiferromagnetic behavior.     

Effect of Functionalized Groups on Gas‐Adsorption Properties: Syntheses of Functionalized Microporous Metal–Organic Frameworks and Their High Gas‐Storage Capacity

The microporous metal–organic framework (MMOF) Zn₄O(L1)₂ ? 9 DMF ? 9 H₂O ( 1‐H ) and its functionalized derivatives Zn₄O(L1‐CH₃)₂ ? 9 DMF ? 9 H₂O ( 2‐CH₃ ) and Zn₄O(L1‐Cl)₂ ? 9 DMF ? 9 H₂O ( 3‐Cl ) have been synthesized and characterized (H₃L1=4‐[N,N‐bis(4‐methylbenzoic acid)amino]benzoic acid, H₃L1‐CH₃=4‐[N,N‐bis(4‐methylbenzoic acid)amino]‐2‐methylbenzoic acid, H₃L1‐Cl=4‐[N,N‐bis(4‐methylbenzoic acid)amino]‐2‐chlorobenzoic acid). Single‐crystal X‐ray diffraction analyses confirmed that the two functionalized MMOFs are isostructural to their parent MMOF, and are twofold interpenetrated three‐dimensional (3D) microporous frameworks. All of the samples possess enduring porosity with Langmuir surface areas over 1950 cm² g^?1. Their pore volumes and surface areas decrease in the order 1‐H > 2‐CH₃ > 3‐Cl . Gas‐adsorption studies show that the H₂ uptakes of these samples are among the highest of the MMOFs (2.37 wt % for 3‐Cl at 77 K and 1 bar), although their structures are interpenetrating. Furthermore, this work reveals that the adsorbate–adsorbent interaction plays a more important role in the gas‐adsorption properties of these samples at low pressure, whereas the effects of the pore volumes and surface areas dominate the gas‐adsorption properties at high pressure.     

Hydrogen Storage in a Potassium‐Ion‐Bound Metal–Organic Framework Incorporating Crown Ether Struts as Specific Cation Binding Sites

To develop a metal–organic framework (MOF) for hydrogen storage, SNU‐200 incorporating a 18‐crown‐6 ether moiety as a specific binding site for selected cations has been synthesized. SNU‐200 binds K⁺, NH₄⁺, and methyl viologen(MV²⁺) through single‐crystal to single‐crystal transformations. It exhibits characteristic gas‐sorption properties depending on the bound cation. SNU‐200 activated with supercritical CO₂ shows a higher isosteric heat (Q_st) of H₂ adsorption (7.70 kJ mol^?1) than other zinc‐based MOFs. Among the cation inclusions, K⁺ is the best for enhancing the isosteric heat of the H₂ adsorption (9.92 kJ mol^?1) as a result of the accessible open metal sites on the K⁺ ion.     

(3,4)‐Connected Twofold Interpenetrated Network with Right‐ and Left‐Handed Helical Chains: Synthesis,Crystal Structure,and Luminescence Sensing

The zinc(II) coordination polymer Zn₂(L)₂(bix)₂ · 2H₂O ( 1 ) [H₂L = 4,4′‐methylenebis(oxy)dibenzoic acid, bix = 1,4‐bis(imidazole‐1‐yl‐methylene)‐benzene] was synthesized by hydrothermal reaction. The title compound was characterized by single‐crystal X‐ray diffraction analysis, IR spectroscopy, and elemental analysis. The crystal structure determination reveals that compound 1 displays a twofold interpenetrated 3D framework, in which the Zn atoms are connected by the H₂L ligands into interesting right and left‐handed helical chains. Topological analysis reveals that the title compound displays a (3,4)‐connected (6³) (6⁵ · 8) topology. The solid‐state luminescent spectra was studied. Furthermore, the dispersed solution of compound 1 in DMF exhibits strong fluorescent emission, which could be quenched by trace amount of nitrobenzene.     

Synthesis,Characterization and Crystal Structure of 4‐Amino‐1,2,4‐Δ2‐triazoline‐5‐thione and its Silver(I) Complex

The reaction of 4‐amino‐1,2,4‐Δ²‐triazoline‐5‐thione (ATT, 1 ) with AgNO₃ in methanol led to the complex [Ag(ATT)₂]NO₃ ( 2 ). 2 was characterized by elemental analyses, ¹H NMR, IR, and Raman spectroscopy as well as single‐crystal X‐ray diffraction. The molecular structure of 1 was also determined by single crystal X‐ray analysis. Crystal data for 1 at ?80 C: space group C2/c with a = 2107.4(2), b = 1425.1(1), c = 688.4(1) pm, β = 104.55(1)°, Z = 16, R₁ = 0.0514, crystal data for 2 at ?80 °C: space group P2₁/c with a = 675.7(1), b = 1321.1(1), c = 1311.2(1) pm, β = 90.03(1)°, Z = 4, R₁ = 0.0437.     

Single‐Crystal‐to‐Single‐Crystal Installation of Ln4(OH)4 Cubanes in an Anionic Metallosupramolecular Framework

Postsynthetic installation of lanthanide cubanes into a metallosupramolecular framework via a single‐crystal‐to‐single‐crystal (SCSC) transformation is presented. Soaking single crystals of K₆[Rh₄Zn₄O(l ‐cys)₁₂] (K₆[ 1 ]; l ‐H₂cys=l ‐cysteine) in a water/ethanol solution containing Ln(OAc)₃ (Ln³⁺=lanthanide ion) results in the exchange of K⁺ by Ln³⁺ with retention of the single crystallinity, producing Ln₂[ 1 ] ( 2_Ln ) and Ln_0.33[Ln₄(OH)₄(OAc)₃(H₂O)₇][ 1 ] ( 3_Ln ) for early and late lanthanides, respectively. While the Ln³⁺ ions in 2_Ln exist as disordered aqua species, those in 3_Ln form ordered hydroxide‐bridged cubane clusters that connect [ 1 ]^6? anions in a 3D metal‐organic framework through coordination bonds with carboxylate groups. This study shows the utility of an anionic metallosupramolecular framework with carboxylate groups for the creation of a series of metal cubanes that have great potential for various applications, such as magnetic materials and heterogeneous catalysts.     

Single Crystal‐to‐Single Crystal Site‐Selective Postsynthetic Metal Exchange in a Zn–MOF Based on Semi‐Rigid Tricarboxylic Acid and Access to Bimetallic MOFs

The metal ions in a neutral Zn–MOF constructed from tritopic triacid H₃L with inherent concave features, rigid core, and peripheral flexibility are found to exist in two distinct SBUs, that is, 0D and 1D. This has allowed site‐selective postsynthetic metal exchange (PSME) to be investigated and reactivities of the metal ions in two different environments in coordination polymers to be contrasted for the first time. Site‐selective transmetalation of Zn ions in the discrete environment is shown to occur in a single crystal‐to‐single crystal (SCSC) fashion, with metal ions such as Fe³⁺, Ru³⁺, Cu²⁺, Co²⁺, etc., whereas those that are part of 1D SBU sustain structural integrity, leading to novel bimetallic MOFs, which are inaccessible by conventional approaches. To the best of our knowledge, site‐selective postsynthetic exchange of an intraframework metal ion in a MOF that contains metal ions in discrete as well as polymeric SBUs is heretofore unprecedented.     

Borromean‐Entanglement‐Driven Assembly of Porous Molecular Architectures with Anion‐Modified Pore Space

A series of metal–organic frameworks based on a flexible, highly charged Bpybc ligand, namely 1? Mn?OH^?, 2? Mn?SO₄^2?, 3? Mn?bdc^2?, 4? Eu?SO₄^2? (H₂BpybcCl₂=1,1′‐bis(4‐carboxybenzyl)‐4,4′‐bipyridinium dichloride, H₂bdc=1,4‐benzenedicarboxylic acid) have been obtained by a self‐assembly process. Single‐crystal X‐ray‐diffraction analysis revealed that all of these compounds contained the same n‐fold 2D→3D Borromean‐entangled topology with irregular butterfly‐like pore channels that were parallel to the Borromean sheets. These structures were highly tolerant towards various metal ions (from divalent transition metals to trivalent lanthanide ions) and anion species (from small inorganic anions to bulky organic anions), which demonstrated the superstability of these Borromean linkages. This non‐interpenetrated entanglement represents a new way of increasing the stability of the porous frameworks. The introduction of bipyridinium molecules into the porous frameworks led to the formation of cationic surface, which showed high affinities to methanol and water vapor. The distinct adsorption and desorption isotherms of methanol vapor in four complexes revealed that the accommodated anion species (of different size, shape, and location) provided a unique platform to tune the environment of the pore space. Measurements of the adsorption of various organic vapors onto framework 1? Mn?OH^? further revealed that these pores have a high adsorption selectivity towards molecules with different sizes, polarities, or π‐conjugated structures.     

Poly[[diaquabis[μ2‐2‐(4‐pyridinio)propane‐1,3‐dionato‐κ2O:O′]cobalt(II)] dinitrate]

The title compound, {[Co(C₈H₇NO₂)₂(H₂O)₂](NO₃)₂}_n, is the first d‐metal ion complex involving bidentate bridging of a β‐dialdehyde group. The Co²⁺ ion is situated on an inversion centre and adopts an octahedral coordination with four equatorial aldehyde O atoms [Co—O = 2.0910 (14) and 2.1083 (14) Å] and two axial aqua ligands [Co—O = 2.0631 (13) Å]. The title compound has a two‐dimensional square‐grid framework structure supported by propane‐1,3‐dionate O:O′‐bridges between the metal ions. The organic ligand itself possesses a zwitterionic structure, involving conjugated anionic propane‐1,3‐dionate and cationic pyridinium fragments. Hydrogen bonding between coordinated water molecules, the pyridinium NH group and the nitrate anions [O...O = 2.749 (2) and 2.766 (3) Å, and N...O = 2.864 (3) Å] is essential for the crystal packing.     

The Quasi‐Binary Acetonitriletriide Sr3[C2N]2

The first quasi‐binary acetonitriletriide Sr₃[C₂N]₂ has been synthesised and characterised. The nearly colourless crystals were obtained from the reaction of Sr metal, graphite, and elemental N₂, generated by decomposition of Sr(N₃)₂, in a sealed Ni ampoule with the aid of an alkali metal flux. The structure of this compound was analysed via single‐crystal X‐ray diffraction and the identity of the [C₂N]^3? anion was confirmed by Raman spectroscopy and further investigated by quantum‐chemical methods. Computed interatomic distances within the [C₂N]^3? anion strikingly match the obtained experimental data.     

Effect of Bulkiness on Reversible Substitution Reaction at MnII Center with Concomitant Movement of the Lattice DMF: Observation through Single‐Crystal to Single‐Crystal Fashion

The porous coordination polymer ({[Mn(L)H₂O](H₂O)_1.5(dmf)}_n, 1 ) (DMF=N,N‐dimethylformamide) exhibits variety of substitution reactions along with movement of lattice DMF molecule depending upon bulkiness of the external guest molecules. If pyridine or 4‐picoline is used as a guest, both lattice and coordinated solvent molecules are simultaneously substituted (complexes 6 and 7 , respectively). If a bulky guest like aniline is used, a partial substitution at the metal centers and full substitution at the channels takes place (complex 8 ). If the guest is 2‐picoline (by varying the position of bulky methyl group with respect to donor N atom), one Mn^II center is substituted by 2‐picoline, whereas the remaining center is substituted by a DMF molecule that migrates from the channel to the metal center (complex 9 ). Here, the lattice solvent molecules are substituted by 2‐picoline molecules. For the case of other bulky guests like benzonitrile or 2,6‐lutidine, both the metal centers are substituted by two DMF molecules, again migrating from the channel, and the lattice solvent molecules are substituted by these guest molecules (complex 10 and 11 , respectively). A preferential substitution of pyridine over benzonitrile (complex 12 ) at the metal centers is observed only when the molar ratio of PhCN:Py is 95:5 or less. For the case of an aliphatic dimethylaminoacetonitrile guest, the metal centers remain unsubstituted (complex 13 ); rather substitutions of the lattice solvents by the guest molecules take place. All these phenomena are observed through single crystal to single crystal (SC–SC) phenomena.