Search

The increased anthropogenic emission level of CO 2 urges the development of CO 2 -responsive materials, but is it possible to regulate the inherent electronic properties through weak physisorption of a ubiquitous gas such as CO 2 ? Herein, we intended to answer this imperative question by the first case of CO 2 -actuated variable spin-state stabilisation in an interdigitated Hofmann-type coordination polymer [Fe II Pd(CN) 4 L 2 ] (1, L = methyl isonicotinate), showing a wide shift in transition temperature ( T eq ) from 178 K at P CO 2 = 0 kPa to 229 K at P CO 2 = 100 kPa. Interestingly, the emergence of a stepped behaviour in the heating process below P CO 2 = 10 kPa and overlapping magnetic susceptibility values above P CO 2 = 10 kPa elucidate the selective LS state stabilisation solely correlated with the extent of CO 2 accommodation. Based on the magnetic response and phase transition diagrams obtained under respective P CO 2 , a plausible scenario of the spin-state switching can be interpreted as (1 ls + ) → (1 hs + ) → 1 hs at P CO 2 ≤ 10 kPa, → 1 hs at 100 kPa < P CO 2 ≥ 32 kPa and → → 1 hs at 100 kPa, where 1 and 1' represent CO 2 -free and CO 2 -encapsulated states, respectively. The cooperative CO 2 sorption with SCO based on the varied CO 2 pressure corroborates a novel case for developing CO 2 -responsive magnetic materials henceforth., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Purpose: Minimally invasive surgery for gastrointestinal cancers is rapidly advancing; therefore, surgical education must be changed. This study aimed to examine the feasibility of early initiation of robotic surgery education for surgical residents., Methods: The ability of staff physicians and residents to handle robotic surgical instruments was assessed using the da Vinci ® skills simulator (DVSS). The short-term outcomes of 32 patients with colon cancer who underwent robot-assisted colectomy (RAC) by staff physicians and residents, supervised by a dual console system, between August 2022 and March 2024 were compared., Results: The performances of four basic exercises were assessed after implementation of the DVSS. Residents required less time to complete these exercises and achieved a higher overall score than staff physicians. There were no significant differences in the short-term outcomes, operative time, blood loss, incidence of postoperative complications, and length of the postoperative hospital stay of the two surgeon groups., Conclusion: Based on the evaluation involving the DVSS and RAC results, it appears feasible to begin robotic surgery training at an early stage of surgical education using a dual console system., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The paddlewheel-type dimetal core ([M 2 ]) is a ubiquitous motif in the nodes in coordination polymers (CPs) and metal-organic frameworks (MOFs). However, their preparation has relied on ligand-substitution-labile metal ions owing to challenges associated with crystallization. Consequently, examples featuring ligand-substitution-inert metal ions, such as Ru or Rh, are scarce. This study presents the synthesis of novel reticular imine-linked CPs incorporating the paddlewheel-type diruthenium(II, II) ([Ru 2 II,II ]; 1-Ru) or dirhodium(II, II) ([Rh 2 II,II ]; 1-Rh) subunits. The synthetic approach involved a Schiff base dehydration condensation reaction between p-formylbenzoate-bridged [Ru 2 II,II ] or [Rh 2 II,II ] precursors (i. e., CHO-Ru and CHO-Rh, respectively) and 2,5-dimethyl-1,4-phenylenediamine in a 1 : 2 ratio. The catalytic activities of 1-Ru and 1-Rh for the photochemical reduction of CO 2 in a heterogeneous system depended on the metal site. The 1-Ru system exhibited exceptional selectivity, generating 3.0×10 4  μmol g -1 of CO after 24 h of irradiation, whereas the 1-Rh system generated a lower amount of CO (3.2×10 3  μmol g -1 ). The catalytic activity of 1-Ru ranked with that of all relevant catalytic systems. This study paves the way for the exploration of [Ru 2 II,II ]- or [Rh 2 II,II ]-based polymers with open metal site-dependent functional properties., (© 2024 The Authors. ChemSusChem published by Wiley-VCH GmbH.)

In [Mn(5-MeOsalen)(Cl)] 2 (dibenzo[24]crown-8), dibenzo[24]crown-8 formed a supramolecule via multi-point interactions with the [Mn(5-MeOsalen)(Cl)] dimer. The dimer was magnetically isolated with S T = 4 and weak interdimer magnetic interactions. The crystal exhibited single-molecule magnet behaviour with an anisotropic barrier of 26(1) K, which is the highest among the Mn-salen series reported to date.

A new synthetic route for constructing functional paddlewheel diruthenium(II,II) complexes ([RuII,II2]) was developed by utilizing Schiff base condensation reactions of formyl-substituted benzoate-bridged [RuII,II2] complexes with various aromatic monoamines under mild conditions. Cyclic voltammetry and DFT calculations revealed that the attached Schiff base groups significantly affected the electronic states of the resulting [RuII,II2] complexes.

Porous magnets that undergo a magnetic phase transition in response to gaseous adsorbates are desirable for the development of sustainable sensing and memory devices. Familiar gases such as O 2 and CO 2 are one class of target adsorbates because of their close association with life sciences and environmental issues; however, it is not easy to develop magnetic devices that respond to these ubiquitous gases. To date, only three examples of gas-responsive magnetic phase transitions have been demonstrated: (i) from a ferrimagnet to an antiferromagnet, (ii) its vice versa (i.e., change of magnetic phase), and (iii) from a ferrimagnet to a paramagnet (i.e., erasure of the magnetic phase). However, the creation of a magnet, meaning the change from a nonmagnet to a magnet by O 2 or CO 2 gas adsorption and magnetic switching by this phenomenon have not yet been explored. Herein, we report a CO 2 -induced antiferromagnet modified from a paramagnetic charge-flexible layered compound, [{Ru 2 (2,4-F 2 PhCO 2 ) 4 } 2 TCNQ(OEt) 2 ] ( 1 ; 2,4-F 2 PhCO 2 - = 2,4-difluorobenzoate; TCNQ(OEt) 2 = 2,5-diethoxy-7,7,8,8-tetracyanoquinodimethane), where three molar equivalents of CO 2 was accommodated at a CO 2 pressure of 100 kPa. The magnetic change originates from charge fluctuation due to the transfer of electrons moving from the electron-donor to the electron-acceptor unit or vice versa, resulting in a change in the electron distribution induced by CO 2 adsorption/desorption in the donor-acceptor-type charge transfer framework. Owing to the reversible electronic state change upon CO 2 adsorption/desorption, these magnetic phases are switched, accompanied by modification of the electrical conductivity, which is boosted by the CO 2 accommodation. This is the first example of the creation of a CO 2 -responsive magnet, which is promising for novel molecular multifunctional devices.

Partial charge fluctuations in the charge-ordered state of a material, often triggered by structural disorders and/or defects, can significantly alter its physical characteristics, such as magnetic long-range ordering. However, it is difficult to post-chemically fix such accidental partial fluctuations to reconstruct a uniform charge-ordered state. Herein, we report CO 2 -aided charge ordering demonstrated in a CO 2 -post-captured layered magnet, [{Ru 2 (o-ClPhCO 2 ) 4 } 2 {TCNQ(OMe) 2 }] ⋅ CO 2 (1⊃CO 2 ; o-ClPhCO 2 - =ortho-chlorobenzoate; TNCQ(OMe) 2 =2,5-dimethoxy-7,7,8,8-tetracyanoquinodimethane). Pristine porous layered magnet 1 had a partially charge-fluctuated ordered state, which provided ferrimagnetic ordering at T C =65 K. Upon loading CO 2 , 1 adsorbed one mole of CO 2 , forming 1⊃CO 2 , and raising T C to 100 K. This was because of the vanishing charge fluctuations without significantly changing the framework structure. This research illustrates the post-accessible host-guest chemistry delicately combined with charge, spin, and lattice ordering in a spongy magnet. Furthermore, it highlights how this innovative approach opens up new possibilities for technology and nanoscale magnetism manipulation., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Iron(ii) spin cross-over (SCO) compounds combine a thermally driven transition from the diamagnetic low-spin (LS) state to the paramagnetic high-spin (HS) state with a distinct change in the crystal lattice volume. Inversely, if the crystal lattice volume was modulated post-synthetically, the spin state of the compound could be tunable, resulting in the inverse effect for SCO. Herein, we demonstrate such a spin-state tuning in a breathing cyanido-bridged porous coordination polymer (PCP), where the volume change resulting from guest-induced gate-opening and -closing directly affects its spin state. We report the synthesis of a three-dimensional coordination framework {[Fe II (4-CNpy) 4 ] 2 [W IV (CN) 8 ]·4H 2 O} n (1·4H 2 O; 4-CNpy = 4-cyanopyridine), which demonstrates a SCO phenomenon characterized by strong elastic frustration. This leads to a 48 K wide hysteresis loop above 140 K, but below this temperature results in a very gradual and incomplete SCO transition. 1·4H 2 O was activated under mild conditions, producing the nonporous {[Fe II (4-CNpy) 4 ] 2 [W IV (CN) 8 ]} n (1) via a single-crystal-to-single-crystal process involving a 7.3% volume decrease, which shows complete and nonhysteretic SCO at T 1/2 = 93 K. The low-temperature photoswitching behavior in 1 and 1·4H 2 O manifested the characteristic elasticity of the frameworks; 1 can be quantitatively converted into a metastable HS state after 638 nm light irradiation, while the photoactivation of 1·4H 2 O is only partial. Furthermore, nonporous 1 adsorbed CO 2 molecules in a gated process, leading to {[Fe II (4-CNpy) 4 [W 2 [W IV (CN) 8 ]·4CO 2 } n (1·4CO 2 ), which resulted in a 15% volume increase and stabilization of the HS state in the whole temperature range down to 2 K. The demonstrated post-synthetic guest-exchange employing common gases is an efficient approach for tuning the spin state in breathing SCO-PCPs., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A luminescent three-dimensional coordination polymer (CP) of [Cd II (pmd){Ag I (CN) 2 } 2 ] (1; pmd = pyrimidine) comprising two different coordination modes of Ag + ions was synthesised herein. 1 exhibited thermochromic luminescence, accompanied by positive thermal elongation of the Ag⋯Ag distance. Moreover, 1 showed a bright phosphorescence with the highest photoluminescence quantum yield ( Φ em ), approximately 60% at room temperature, among previously reported phosphorescent Ag-based CPs or metal-organic frameworks.

Magnetism of layered magnets depends on the inter-layer through-space magnetic interactions ( J NNNI ). Using guest sorption to address inter-layer pores in bulk-layered magnets is an efficient approach to magnetism control because the guest-delicate inter-layer distance ( l trans ) is a variable parameter for modulating J NNNI . Herein, we demonstrated magnetic changes induced by the adsorption of CO 2 , N 2 , and O 2 gases in various isostructural layered magnets with a π-stacked pillared-layer framework, , (M = Co, 1, Fe, 2, Cr, 3; Cp* = η 5 -C 5 Me 5 ; 2,3,5,6-F 4 PhCO 2 - = 2,3,5,6-tetrafluorobenzoate; TCNQ = 7,7,8,8-tetracyano- p -quinodimethane). Each compound had almost identical adsorption capability for the three types of gases; only CO 2 adsorption was found to have a gated profile. A breathing-like structural modulation involving the extension of l trans occurred after the insertion of gases into the isolated pores between the [Ru 2 ] 2 -TCNQ ferrimagnetic layers, which is more significant for CO 2 than for O 2 and N 2 , due to the CO 2 -gated transition. While adsorbent 1 with M = Co ( S = 0) was an antiferromagnet with T N = 75 K, 1⊃CO 2 was a ferrimagnet with T C = 76 K, whereas 1⊃N 2 and 1⊃O 2 were antiferromagnets with T N = 68 K. The guest-insertion effect was similarly confirmed in 2 and 3, and was characteristically dependent on the type of sandwiched spin in as M = Fe ( S = 1/2) and Cr ( S = 3/2), respectively. This study reveals that common gases such as CO 2 , O 2 , and N 2 can serve as crucial triggers for the change in magnetism as a function of variable parameter l trans ., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Low-dimensional coordination polymers such as one-dimensional chains often exhibit gated guest sorption accompanying structural transition at a temperature ( T G ), which is associated with an external pressure of the guest ( P G ) characteristic to the material and guest used. This phenomenon can be evaluated using the Clausius-Clapeyron relationship with the equation d( ln P G )/d(1/ T G ) = ΔH G / R , where Δ H G and R are the transition enthalpy and gas constant, respectively. In this study, gated CO 2 adsorption behavior was investigated in a one-dimensional chain based on a benzoate-bridged paddlewheel diruthenium(II,II) complex with a phenazine (phz) linker, [Ru 2 ( p -MeOPhCO 2 ) 4 (phz)] ( 1 ; p -MeOPhCO 2 - = p -anisate). Surprisingly, 1 underwent gate opening (GO)/closing (GC) at a much higher T G , e.g., 385 K for GC, under P CO 2 = 100 kPa than those previously reported for such chain compounds, which usually appeared in the temperature range of 200-270 K. The transition entropy Δ S G in each system plays a key role in shifting T G ; 1 results in a much smaller |Δ S G | in the series. Only 1 produced a CO 2 -accessible two-dimensional topological pore in its CO 2 -adsorbed phase 1⊃CO 2 , whereas the others reported previously produced one-dimensional or discrete topological pores for CO 2 accommodation, strongly reflecting the degree of freedom of CO 2 molecules in pores, which is related to Δ S G .

The coordination polymers (CPs) with binary ligands, including 2,5-dihydroxy-1,4-benzoquinone (H2DHBQ) and 4,4'-bipyridyl (bpy), were synthesized using in situ hydrolysis of 2,5-dimethoxy-1,4-benzoquinone (DMBQ). Three kinds of CPs were obtained depending on the metal ions. For M = Mn and Zn, a 1D zigzag chain structure with cis conformation ( cis -1D-M ) was obtained, whereas Co, Ni, and Cu compounds afforded a 2D net structure with trans conformation ( trans -2D-M ) with a 1D pore. A linear chain structure was also obtained for M = Cu. Magnetic susceptibility (χ M T ) at 300 K in cis -1D-Mn and trans -2D-Co was evaluated to be 4.421 and 2.950 cm 3 K mol -1 , respectively, indicating that both compounds are in the high-spin state. According to the N 2 adsorption isotherms at 77 K, trans -2D-Ni showed microporosity with the BET surface area of 177 m 2 g -1 , whereas the isomorphic trans -2D-Co rarely adsorbed N 2 at 77 K. This phenomenon was explained by the difference of diffusion kinetics of the adsorbent molecules, which was supported by the CO 2 adsorption isotherms at 195 K. The optical band gaps of cis -1D-Mn , cis -1D-Zn , trans -2D-Co , and trans -2D-Ni were estimated to be 1.6, 1.8, 1.0, and 1.1 eV, respectively, by using UV-vis-NIR spectroscopy., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Host-guest electron transfer (HGET) in molecular framework systems is a critical trigger for drastic functional changes in both host framework and guest. A reversible magnetic phase transition was achieved via HGET in a layered framework, [{Ru 2 (2,6-F 2 PhCO 2 ) 4 } 2 (BTDA-TCNQ)] (1), where 2,6-F 2 PhCO 2 - and BTDA-TCNQ represent 2,6-difluorobenzoate and bis[1,2,5]dithiazolotetracyanoquinodimethane, respectively. The guest-free 1 with an antiferromagnetic ground state transformed into a paramagnet, [{Ru 2 (2,6-F 2 PhCO 2 ) 4 } 2 (BTDA-TCNQ)]I 3 (1-I 3 ), by adsorbing iodine (I 2 ). The local charge distribution of [{Ru 2 II,III } + -(BTDA-TCNQ) .- -{Ru 2 II,II }] in 1 was reversibly modified to [{Ru 2 II,III } + -(BTDA-TCNQ) 0 -{Ru 2 II,II }](I 3 - ) in 1-I 3 through HGET. Theoretical calculations of 1-I 3 indicated a partial charge delocalization as [{Ru 2 } (1-δ)+ -(BTDA-TCNQ) 0 -{Ru 2 } δ+ ](I 3 - ) with δ≈0.2, aided by weak ferromagnetic coupling. 1-I 3 exhibited a hundred-fold enhancement in electrical conductivity compared to that of 1., (© 2022 Wiley-VCH GmbH.)

The synthesis of a series of trans -heteroleptic paddlewheel diruthenium(II,II) complexes with various hydroxy-substituted benzoate ligands, [Ru 2 ((OH) x PhCO 2 ) 2 (2,6-(CF 3 ) 2 PhCO 2 ) 2 (THF) 2 ] ([RuII,II2]) as tetrahydrofuran (THF) adducts is reported, where (OH) x PhCO 2 - stands for o -hydroxybenzoate (o-OH), m -hydroxybenzoate (m-OH), p -hydroxybenzoate (p-OH), 2,3-dihydroxybenzoate (2,3-(OH)2), 2,4-dihydroxybenzoate (2,4-(OH)2), 2,5-dihydroxybenzoate (2,5-(OH)2), 2,6-dihydroxybenzoate (2,6-(OH)2), or 3,4-dihydroxybenzoate (3,4-(OH)2), and 2,6-(CF 3 ) 2 PhCO 2 - represents 2,6-bis(trifluoromethyl)benzoate. In this heteroleptic series, the redox potential ( E 1/2 ) of the [RuII,II2]/[RuII,III2] + couple in THF varies over a wide range, from -18 mV ( vs. Ag/Ag + ) for p-OH to 432 mV for 2,6-(OH)2. The redox properties are linearly dependent on the acidity (p K a ) of the OH-substituted benzoic acids, but do not depend on the number of ortho -substituted hydroxy ( o -OH) groups. This indicates that the steric effect of o -substituents is irrelevant in the case of hydroxyl groups, owing to the formation of intramolecular hydrogen bonds between the o -OH group and carboxylate oxygens. The value of the Hammett constant σ o for the o -OH substituent was determined to be 0.667, indicating a strongly electron-withdrawing character, contrary to the expectation of electron-donating character for an OH group. The redox properties of the compounds were well explained in a framework of Hammett analyses and were also consistent with their HOMO energy levels evaluated by DFT calculations based on the atomic coordinates. The unexpected electron-withdrawing character of the o -OH groups could be attributed to the direct effect of intramolecular hydrogen bonding on the charge density on the carboxylate oxygen.

The combination of a cobalt-dioxolene core that exhibits valence tautomerism (VT) with pyridine-3,5-dicarboxylic acid functionalized with chains bearing two, four, or six oxyethylene units led to new complexes ConEGEspy (n = 2, 4, and 6). These complexes commonly form violet crystals of the low-spin (ls)-[Co III (nEGEspy) 2 (3,6-DTBSQ)(3,6-DTBCat)] (ls-[Co III ], 3,6-DTBSQ = 3,6-di-tert-butyl semiquinonato, 3,6-DTBCat = 3,6-di-tert-butyl catecholato). Interestingly, violet crystals of Co2EGEspy in the ls-[Co III ] transitioned into a green liquid, accompanied by an almost complete VT shift (94 %) to the high-spin (hs)-[Co II (nEGEspy) 2 (3,6-DTBSQ) 2 ] (hs-[Co II ]) upon melting. In contrast, violet crystals of Co4EGEspy and Co6EGEspy in the ls-[Co III ] exhibited partial VT (33 %) and only a 9.3 % VT shift after melting, respectively. These data demonstrate the tunability of the synchronicity of the molecular VT and macroscopic solid-liquid transitions by optimizing the tethered chains, thus establishing a new strategy for coupling bistable molecules with the macroscopic world., (© 2021 Wiley-VCH GmbH.)

A novel porous magnet consisting of cationic two-dimensional (2-D) layers extended by Fe III -CN-Ni II linkages and pseudo-pillar dianions was synthesized. The size-selective guest adsorption behaviour of water and methanol molecules originates from the narrow bottle-neck-type pores in the flexible pseudo-pillared-layer structure, which results in the switching of the magnetic phases from antiferromagnetic to ferromagnetic, involving significant changes in the interlayer distance.

Changing nonmagnetic materials to spontaneous magnets is an alchemy-inspiring concept in materials science; however, it is not impossible. Here, we demonstrate chemical modification from a nonmagnet to a bulk magnet of either a ferrimagnet or antiferromagnet, depending on the adsorbed guest molecule, in an electronic-state-flexible layered metal-organic framework, [{Ru 2 (2,4-F 2 PhCO 2 ) 4 } 2 TCNQ(EtO) 2 ] ( 1 ; 2,4-F 2 PhCO 2 - = 2,4-difluorobenzoate; TCNQ(EtO) 2 = 2,5-diethoxy-7,7,8,8-tetracyanoquinodimethane). The guest-free paramagnet 1 undergoes a thermally driven intralattice electron transfer involving a structural transition at 380 K. This charge modification can also be implemented by guest accommodations at room temperature; 1 adsorbs several organic molecules, such as benzene (PhH), p -xylene (PX), 1,2-dichloroethane (DCE), dichloromethane (DCM), and carbon disulfide (CS 2 ), forming 1-solv with intact crystallinity. This induces an intralattice electron transfer to produce a ferrimagnetically ordered magnetic layer. According to the interlayer environment tuned by the corresponding guest molecule, the magnetic phase is consequently altered to a ferrimagnet for the guests PhH, PX, DCE, and DCM or an antiferromagnet for CS 2 . This is the first demonstration of the postsynthesis of bulk magnets using guest-molecule accommodations.

Recent developments in research concerning metal-organic frameworks and coordination polymers have provided the successful design of charge-variable molecular frameworks. However, few comprehensive studies exist that investigate the control of charge states in series of molecular frameworks such as these. Herein, we discuss the ionicity diagrams of two series containing electron-donor (D) and -acceptor (A) units: one-dimensional DA chains and two-dimensional D 2 A layers. The series were obtained by reacting paddlewheel-type diruthenium(II,II) complexes ([Ru 2 II,II ]), which served as D units, with the polycyano-organic acceptors N , N' -dicyanoquinodiimine (DCNQI) and 7,7,8,8-tetracyano- p -quinodimethane (TCNQ), which served as A units. Fifteen novel members of neutral charged DA chains were fabricated in this study to characterize the ionicity diagrams for DA and D 2 A systems.

With adequate building blocks, metal-organic frameworks (MOFs) can combine magnetic ordering and porosity. This makes MOFs a promising platform for the development of stimuli-responsive materials that show drastically different magnetic properties depending on the presence or absence of guest molecules within their pores. Here we report a CO 2 -responsive magnetic MOF that converts from ferrimagnetic to paramagnetic on CO 2 adsorption, and returns to the ferrimagnetic state on CO 2 desorption. The ferrimagnetic material is a layered MOF with a [D + -A - -D] formula, produced from the reaction of trifluorobenzoate-bridged paddlewheel-type diruthenium(II) clusters as the electron donor (D) with diethoxytetracyanoquinodimethane as the electron acceptor (A). On CO 2 uptake, it undergoes an in-plane electron transfer and a structural transition to adopt a [D-A-D] paramagnetic form. This magnetic phase change, and the accompanying modifications to the electronic conductivity and permittivity of the MOF, are electronically stabilized by the guest CO 2 molecules accommodated in the framework.

Molecular motions taking place in the nanospace of metal-organic frameworks (MOFs) are an interesting research subject, although not yet fully investigated. In this work, we utilized in situ Raman spectroscopy in the ultralow-frequency region to investigate the libration motion (including the rotational motion of phenylene rings) of MOFs, in particular [Cu 2 (bdc) 2 (dabco)] (Cu-JAST-1), where bdc = 1,4-benzenedicarboxylate and dabco = 1,4-diazabicyclo[2.2.2]octane. The libration mode of Cu-JAST-1 was found to be significantly suppressed by the adsorption of various guest molecules, such as CO 2 , Ar, and N 2 . In addition, an appreciable correlation between the libration mode and adsorption equilibrium time was identified, which provides useful novel tools in the design of MOFs acting as molecular adsorption and separation materials.

The insertion of "sandwiched spins" between magnetic layers could efficiently affect the interlayer magnetic correlations, but doing so increases the complexity in the interlayer spin alignment because of competition between the inserted spin-layer interaction J NNI and the interlayer through-space interaction J NNNI if the magnitude of J NNI is of the same order as J NNNI with reciprocal signs of the respective interactions. Herein, systematic tuning of the magnetic phase variations by J NNI and J NNNI in two kinds of metal-variable isostructural series of supramolecular pillared layer magnets [MCp* 2 ][{Ru 2 II,II (2,3,5,6-F 4 CO 2 ) 4 } 2 (TCNQ)]⋅2 DCE (M=Co, Fe, Cr; 2,3,5,6-F 4 PhCO 2 - =2,3,5,6-tetrafluorobenzoate; TCNQ=7,7,8,8-tetracyano-p-quinodimethane; DCE=1,2-dichloroethane) and their DCE-free series, in which [MCp* 2 ] + (Cp*=η 5 -C 5 Me 5 ) species with S=0, 1/2, and 3/2 for M=Co, Fe, Cr, respectively, are sandwiched between ferrimagnetic layers of [{Ru 2 } 2 (TCNQ)] - , is demonstrated. The results showed that the flexible magnetic natures of these magnets are changeable in dependence on J NNI and J NNNI , as well as on interlayer inserted spins M., (© 2020 Wiley-VCH GmbH.)

Herein, we synthesized four isostructural flexible interdigitated hydrophobic metal-organic frameworks that differ only in their central metal ion. The water-adsorption properties are dependent on the metal species, which was revealed to be caused by coordination distortion around the metal ions.

CO 2 -responsive spin-state conversion between high-spin (HS) and low-spin (LS) states at room temperature was achieved in a monomeric cobalt(II) complex. A neutral cobalt(II) complex, [Co II (COO-terpy) 2 ]⋅4 H 2 O (1⋅4 H 2 O), stably formed cavities generated via π-π stacking motifs and hydrogen bond networks, resulting in the accommodation of four water molecules. Crystalline 1⋅4 H 2 O transformed to solvent-free 1 without loss of porosity by heating to 420 K. Compound 1 exhibited a selective CO 2 adsorption via a gate-open type of the structural modification. Furthermore, the HS/LS transition temperature (T 1/2 ) was able to be tuned by the CO 2 pressure over a wide temperature range. Unlike 1 exhibits the HS state at 290 K, the CO 2 -accomodated form 1⊃CO 2 (P CO 2 =110 kPa) was stabilized in the LS state at 290 K, probably caused by a chemical pressure effect by CO 2 accommodation, which provides reversible spin-state conversion by introducing/evacuating CO 2 gas into/from 1., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Molecular materials whose electronic states are multiply varied depending on external stimuli are among the most promising targets for the development of multiply accessible molecular switches. Here, we report a honeycomb layer composed of tetraoxolene-bridged iron (Fe) subunits whose charge-ordered states are multiply variable via thermal treatments and solvation/desolvation with the crystallinity intact. The compound is (NPr 4 ) 2 [Fe 2 (Cl 2 An) 3 ] ( 1-d ; NPr 4 + = tetra- n -propylammonium; Cl 2 An 2- = 2,5-dichloro-3,6-dihydroxo-1,4-benzoquinonate), which possesses three charge-ordered states: a low-temperature (LT) phase [(Fe 3+ ) 2 (Cl 2 An 2- )(Cl 2 An˙ 3- ) 2 ] 2- ; an intermediate (IM) phase [(Fe 2.5+ ) 2 (Cl 2 An 2- )(Cl 2 An 2.5- ) 2 ] 2- ; and a high-temperature (HT) phase [(Fe 2+ ) 2 (Cl 2 An 2- ) 3 ] 2- that varies according to temperature. In addition, the LT phase of 1-d is reversibly changeable to another IM phase in its solvated compound 1 via a solvation/desolvation process at room temperature. This example demonstrates a new multiple-switching system based on electron transfer and host-guest chemistry in a charge-flexible metal-organic framework., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The electron-donor(D) and -acceptor(A)-assembled D 2 A-layer framework [{Ru 2 (m-FPhCO 2 ) 4 } 2 TCNQ(OMe) 2 ]⋅nDCE (1-nDCE; m-FPhCO 2 - =m-fluorobenzoate; TCNQ(OMe) 2 =2,5-dimethoxyl-7,7,8,8-tetracyanoquinodimethane; DCE=1,2-dichloroethane) undergoes drastic charge-ordered state variations via three distinct states that are a two-electron-transferred state (2e-I), a charge-disproportionated state (1.5e-I), and a one-electron-transferred state (1e-I), depending on the degree of solvation by nDCE. The pristine form 1-4DCE has a paramagnetic 2e-I state, which eventually produces the solvent-free form 1 in 1.5e-I via an intermediate state 1-nDCE (n≤1) in 1e-I. Resolvation of 1 stabilizes 1-DCE, allowing it to switch between 1.5e-I and 1e-I, and to become ferrimagnetic with a T c of 30 K (1.5e-I) and 88 K (1e-I). The stabilization of the 1e-I state of 1-DCE is due to the presence of host-guest hydrogen bonding that enables to suppress the electron-donation ability of D even in an identical framework with 1., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Optimal control of gas adsorption properties in metal-organic frameworks (MOFs) or porous coordination polymers (PCPs) remains a great challenge in the field of materials science. An efficient strategy to capture electron-acceptor-type gas molecules such as nitrogen monooxide (NO) is to use host-guest interactions by utilizing electron-donor-type MOFs/PCPs as host frameworks. Herein, we focus on a highly electron-donating chain compound by using the paddlewheel-type [Ru 2 II,II ] complex [Ru 2 (2,4,5-Me 3 PhCO 2 ) 4 ] (2,4,5-Me 3 PhCO 2 - =2,4,5-trimethylbenzoate) with the phenazine (phz) linker: [Ru 2 (2,4,5-Me 3 PhCO 2 ) 4 (phz)] (1). Compound 1 exhibited a specific gated adsorption for NO under gas pressures greater than 60 kPa at 121 K, which finally resulted in approximately seven molar equivalents being taken up at 100 kPa followed by four molar equivalents remaining under vacuum at 121 K; its Rh isomorph (2) with weaker donation ability was inactive for NO. When the sample of 1⊃4 NO was heated to room temperature, the compound underwent a crystal-to-crystal phase transition to give [Ru 2 (2,4,5-Me 3 PhCO 2 ) 4 (NO) 2 ](phz) (1-NO), involving a post-synthetic nitrosylation on the [Ru 2 ] unit, accompanied by an eventful site-exchange with phz. This drastic event, which is dependent on the NO pressure, temperature, and time, was coherently monitored by using several different in situ techniques, revealing that the stabilization of NO molecules in nanosized pores dynamically and stepwisely occurred with the support of strong electronic/magnetic host-guest interactions., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A series of substituted benzoate-bridged dichromium(ii,ii) complexes [Cr2(RCO2)4(THF)2] ([Cr2]), where RCO2- is substituted benzoate, was synthesized and its structural and magnetic properties were investigated. The orbital energies, as well as magnetic coupling energies, were also investigated using computational approaches. The HOMO/LUMO energy levels of the complexes are strongly dependent on the acidity, i.e., pKa, of the corresponding benzoic acids (RCO2H), revealing a linear trend in the respective groups of non-ortho, mono-ortho, and bi-ortho substituted groups. The CrCr magnetic coupling constant (ES-T) is little affected by pKa; instead, the ES-T is associated with the HOMO/LUMO gap and strongly correlated with the CrCr distance.

Gas-sensing materials are becoming increasingly important in our society, requiring high sensitivity to differentiate similar gases like N 2 and O 2 . For the design of such materials, the driving force of electronic host-guest interaction or host-framework changes during the sorption process has commonly been considered necessary; however, this work demonstrates the use of the magnetic characteristics intrinsic to the guest molecules for distinguishing between diamagnetic N 2 and CO 2 gases from paramagnetic O 2 gas. While the uptake of N 2 and CO 2 leads to an increase in T C through ferrimagnetic behavior, the uptake of O 2 results in an O 2 pressure-dependent continuous phase change from a ferrimagnet to an antiferromagnet, eventually leading to a novel ferrimagnet with aligned O 2 spins following application of a magnetic field. This chameleonic material, the first with switchable magnetism that can discriminate between similarly sized N 2 and O 2 gases, provides wide scope for new gas-responsive porous magnets.

A donor (D)/acceptor (A) assembly reaction using the paddlewheel-type diruthenium(ii,ii) complex [Ru2(3,5-F2PhCO2)4(THF)2] (3,5-F2PhCO2- = 3,5-difluorobenzoate; abbreviated hereafter as [Ru2]) as D and 7,7,8,8-tetracyano-p-quinodimethane derivatives (TCNQRx; 2,5-R-substituted TCNQ) as A in a DCM/TCE or DCE solvent system (DCM = dichloromethane, TCE = 1,1,2,2-tetrachloroethane, DCE = 1,2-dichloroethane) led to the formation of D2A-type two-dimensional layered compounds [{Ru2(3,5-F2PhCO2)4}2{TCNQRx}]·nsolv (Rx = H2 (1), Rx = Me2, (2), and Rx = (OEt)2 (3)). All the compounds had similar two-dimensional fishnet-type structures, where the two [Ru2] units were fully coordinated with the four cyano groups of TCNQRx. The compounds 1-3 were categorized as a one-electron transferred ionic state (1e-I) with D+-A--D formulation (D+[triple bond, length as m-dash][RuII,III2]+; A-[triple bond, length as m-dash]TCNQRx˙-). This subunit state formally derived a ferrimagnetically ordered state composed of up-spins with S = 1 for [RuII,II2] and S = 3/2 for [RuII,III2]+ and a down-spin of S = 1/2 for TCNQRx˙-, with antiferromagnetic superexchange interactions in each layer. Eventually, 1-3 became three-dimensional ferrimagnets with Curie temperatures TC = 93, 93, and 92 K, respectively, owing to the presence of interlayer ferromagnetic interactions. The interlayer translational distances (l2) for the three compounds were 10.56, 10.54, and 10.84 Å, respectively, which agreed with the empirical prediction based on the threshold value of l2 > 10.3 Å for a valid ferromagnetic interaction.

Paddlewheel-type carboxylate-bridged dichromium(II,II) complexes possess intriguing properties such as high redox activity and thermally assisted paramagnetism. However, the relationship of their structures with electronic states and physical properties has not been extensively studied. In this work, we investigated a series of one-dimensional chain complexes based on the paddlewheel-type dichromium(II,II) tetraacetate complex ([Cr 2 II,II (OAc) 4 ] = [Cr 2 II,II ]) with pyridine/pyrazine-type organic linkers (μ 2 -L ax ) having different σ- and π-donating abilities to clarify the electronic structure of [Cr 2 II,II ] assemblies. The chain compounds are stable in air, probably owing to their robust polymerized forms. X-ray crystallographic studies and magnetic measurements revealed that the basicity (p K b ) of L ax , which quantitatively correlates with the σ-donor strength of L ax , modulates the Cr-Cr and Cr-L ax distances and the energy separation ( E S-T ) between the diamagnetic (singlet) and thermally populated paramagnetic (triplet) states. The Cr-Cr and Cr-L ax distances are strongly influenced by σ- and π-donation from L ax , while the frontier δ orbital makes only a small contribution to the structural features. Density functional theory calculations were conducted to clarify this issue. The calculations produced the following unanticipated results against the long-known model: (i) the σ bonding orbital is the HOMO and dominates bonding in the [Cr 2 II,II ] unit, (ii) the total Cr-Cr bond order is less than 1.0, and (iii) the δ orbital electron density is almost completely localized on the chromium sites. The computational results accurately predict the magnetic behavior and provide evidence for a new configuration of frontier orbitals in [Cr 2 II,II (RCO 2 ) 4 (L ax ) 2 ].

A reversible magnetic change in response to external stimuli is a desired function of molecular magnetic materials. The magnetic change induced by a change in the intrinsic spin is significant because the magnetic change is inevitable and could become drastic. In this study, we demonstrate a reversible magnetic change closely associated with electronic state modulations, as well as structural modifications realized by solvation/desolvation cycles of a magnetic sponge. The compound was a D 2 A-type layered magnet, [{Ru 2 (O 2 CPh-2,3,5-Cl 3 ) 4 } 2 (TCNQMe 2 )]·4DCM (1; 2,3,5-Cl 3 PhCO 2 - = 2,3,5-trichlorobenzoate; TCNQMe 2 = 2,5-dimethyl-7,7,8,8-tetracyanoquinodimethane; DCM = dichloromethane), where [Ru 2 (O 2 CPh-2,3,5-Cl 3 ) 4 ] ([Ru 2 II,II ]) is an electron donor (D) and TCNQMe 2 is an electron acceptor (A). Compound 1 had a one-electron-transferred, charge-ordered state with a [{Ru 2 II,II }-TCNQMe 2 •- -{Ru 2 II,III } + ] (1e-I) formula. Strong intralayer antiferromagnetic couplings between [Ru 2 II,II ] with S = 1 or [Ru 2 II,III ] + with S = 3/2 and TCNQMe 2 •- with S = 1/2, as well as ferromagnetic interlayer interactions, induced long-range ferrimagnetic ordering at T c = 101 K. Interstitial DCM molecules were located between layers, and these were gradually eliminated under vacuum at 80 °C to form a solvent-free compound (1-dry) without loss of crystallinity. The electronic state of 1-dry thermally fluctuated and eventually provided a charge-disproportionate disordered state, with a [{Ru 2 } 0.5+ -TCNQMe 2 1.5- -{Ru 2 II,III } + ] (1.5e-I) formula as the ground state. The T c in 1-dry was 34 K because of the presence of diamagnetic TCNQMe 2 2- in some parts of the framework. A large T c variation with Δ T c ≈ 70 K was switchable; switching was achieved by charge-state modulations accompanied by subtle structural modifications in solvation/desolvation treatments.

Magnetic phase switching in a coordination polymer is reported, which is demonstrated by combining two processes: (A) the pre-organization of magnetic/redox-active molecules into a framework, and (B) a post-treatment through electrochemical tuning of the pre-organized molecules. A TTF .+ -TCNQ .- salt (TTF=tetrathiafulvalene; TCNQ=7,7,8,8-tetracyano-p-quinodimethane) was incorporated into a three-dimensional framework with paddlewheel-type dimetal(II, II) units ([M 2 II,II ]; M=Ru with S=1, 1; and Rh with S=0, 2), where the [M 2 II,II ] and TCNQ .- units form the coordinating framework, and TTF .+ is located in the pores of framework, forming an irregular π-stacking alternating column with the TCNQ .- in the framework. In 1, the spins of [Ru 2 II,II ] and TCNQ .- units make a magnetic correlation through the framework upon decreasing the temperature from 300 K, which is, however, suddenly suppressed below 137 K (=T d (1)) by the formation of a spin singlet in the TTF .+ -TCNQ .- columns, as seen in the spin-Peierls transition (T d (2)=200 K). This material was incorporated as a cathode in a Li-ion battery (LIB); a long-range ferrimagnetic correlation was formed through the three-dimensional [{Ru 2 II,II } 2 TCNQ] - framework at T c =78 K in the discharge process. The reversible magnetic phase switching between the non-volatile ferrimagnetic and paramagnetic states, resulting from the local spin tuning of quasi-spin-Peierls singlet, is demonstrated through the discharge/charge cycling of the LIB., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Phase transitions caused by the charge instability between the neutral and ionic phases of compounds, i.e., N-I phase transitions, provide avenues for switching the intrinsic properties of compounds related to electron/spin correlation and dipole generation as well as charge distribution. However, it is extremely difficult to control the transition temperature ( T c ) for the N-I phase transition, and only chemical modification based on the original material have been investigated. Here, a design overview of the tuning of N-I phase transition by interstitial guest molecules is presented. This study reports a new chain coordination-polymer [Ru 2 (3,4-Cl 2 PhCO 2 ) 4 TCNQ(EtO) 2 ]∙DCE ( 1-DCE ; 3,4-Cl 2 PhCO 2 - = 3,4-dichlorobenzoate; TCNQ(EtO) 2 2,5-diethoxy-7,7,8,8-tetracyanoquinodimethane; and DCE = 1,2-dichloroethane) that exhibits a one-step N-I transition at 230 K (= T c ) with the N- and I-states possessing a simple paramagnetic state and a ferrimagnetically correlated state for the high- and low-temperature phases, respectively. The T c continuously decreases depending on the content of DCE, which eventually disappears with the complete evacuation of DCE, affording solvent-free compound 1 with the N-state in the entire temperature range (this behavior is reversible). This is an example of tuning the in situ T c for the N-I phase transition via the control of the interstitial guest molecules.

Two ferromagnetic multinuclear Ni(ii) clusters, [Ni 4 L 1 4 (μ 3 -OMe) 4 (CH 3 OH) 4 ] (1) and [Ni 7 (HL 2 ) 6 (μ 3 -OMe) 6 ]Cl 2 (2), and a mononuclear complex [NiL 3 ]·2H 2 O (3) (HL 1 = benzyl 2-hydroxy-3-methoxybenzoate; H 2 L 2 = 1-(2-hydroxy-3-methoxybenzamido)-2-(benzylideneamino)ethane; H 2 L 3 = 1-(2-hydroxy-3-methoxybenzamido)-2-(pyridylmethyleneamino)ethane) were synthesised, and their structures and magnetic behaviours were investigated in detail. 1 has a [Ni 4 O 4 ] cubane structure while 2 has a wheel-like [Ni@Ni 6 ] arrangement. The temperature-dependent magnetic susceptibilities for 1 and 2 are in accord with the presence of dominating intra-cluster ferromagnetic interactions between Ni(ii) ions. The best fits for their behaviours gave the following parameters: J 1 = 11.06 cm -1 , J 2 = 1.43 cm -1 , g = 2.29 for 1, and J 1 = 6.87 cm -1 , J 2 = -3.41 cm -1 , g = 2.24 for 2.

We synthesized cyano-bridged three dimensional metal-organic frameworks [M II (H 2 O) 2 Pt IV (CN) 4 Br 2 ] ∞ ·n(H 2 O) (1: M = Co, 2: M = Ni) with an NbO type topology. Although 1 and 2 have no accessible pores, these MOFs were found to undergo reductive elimination of the axial bromides on the Pt IV ions as well as removal of water molecules upon heating to form porous [M II Pt II (CN) 4 ] ∞ (1': M = Co, 2': M = Ni) with retention of their crystallinity.

On-demand design of porous frameworks for selective capture of specific gas molecules, including toxic gas molecules such as nitric oxide (NO), is a very important theme in the research field of molecular porous materials. Herein, we report the achievement of highly selective NO adsorption through chemical doping in a framework (i.e., solid solution approach): the highly electron donating unit [Ru 2 (o-OMePhCO 2 ) 4 ] (o-OMePhCO 2 - = o-anisate) was transplanted into the structurally flexible chain framework [Ru 2 (4-Cl-2-OMePhCO 2 ) 4 (phz)] (0; 4-Cl-2-OMePhCO 2 - = 4-chloro-o-anisate and phz = phenazine) to obtain a series of doped compounds, [{Ru 2 (4-Cl-2-OMePhCO 2 ) 4 } 1-x {Ru 2 (o-OMePhCO 2 ) 4 } x (phz)] (x = 0.34, 0.44, 0.52, 0.70, 0.81, 0.87), with [Ru 2 (o-OMePhCO 2 ) 4 (phz)] (1) as x = 1. The original compound 1 was made purely from a "highly electron donating unit" but had no adsorption capability for gases because of its nonporosity. Meanwhile, the partial transplant of the electronically advantageous [Ru 2 (o-OMePhCO 2 ) 4 ] unit with x = 0.34-0.52 in 0 successfully enhanced the selective adsorption capability of NO in an identical structurally flexible framework; an uptake at 95 kPa that was 1.7-3 mol/[Ru 2 ] unit higher than that of the original 0 compound was achieved (121 K). The solid solution approach is an efficient means of designing purposeful porous frameworks.

Carboxylate-ligand substitution reactions of paddlewheel-type diruthenium(ii, iii) complexes ([Ru(RCO2)4](+)) with 2,6-bis(trifluoromethyl)benzoate (2,6-(CF3)2PhCO2(-)) involving a selective reduction to [Ru] provide a series of trans-substituted paddlewheel-type diruthenium(ii, ii) complexes, [Ru(2,6-(CF3)2PhCO2)2(RCO2)2(THF)2] (R = CH3, ; C2H5, ; C3H7, ; C4H9, ; C(CH3)3, ; 2,3,5,6-F4Ph, ). Crystal structures of were determined, and their electronic states were investigated by cyclic voltammetry, density functional theory (DFT) and magnetic measurements. This is the first example of trans-heteroleptic carboxylate-bridged [Ru] complexes.

Construction of a molecular system in which the magnetic lattice exhibits long-range order is one of the fundamental goals in materials science. In this study, we demonstrate the artificial construction of a ferrimagnetic lattice by doping electrons into acceptor sites of a neutral donor/acceptor metal-organic framework (D/A-MOF). This doping was achieved by the insertion of Li-ions into the D/A-MOF, which was used as the cathode of a Li-ion battery cell. The neutral D/A-MOF is a layered system composed of a carboxylate-bridged paddlewheel-type diruthenium(II,II) complex as the donor and a TCNQ derivative as the acceptor. The ground state of the neutral form was a magnetically disordered paramagnetic state. Upon discharge of the cell, spontaneous magnetization was induced; the transition temperature was variable. The stability of the magnetically ordered lattice depended on the equilibrium electric potential of the D/A-MOF cathode, which reflected the electron-filling level., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The donor (D)/acceptor (A) assembly reaction of the paddlewheel-type diruthenium(II,II) complex [Ru2(2,4,6-F3PhCO2)4(THF)2] (2,4,6-F3PhCO2(-) = 2,4,6-trifluorobenzoate; abbreviated hereafter as [Ru2]) with 7,7,8,8-tetracyano-p-quinodimethane (TCNQ) in a p-xylene/CH2Cl2 solvent system led to the formation of a two-dimensional layered compound, [{Ru2(2,4,6-F3PhCO2)4}2(TCNQ)]·2(p-xylene)·2CH2Cl2 (1). As expected from this D/A combination, 1 has a one-electron-transfer ionic state with the D(0.5+)2A(-) formulation. This state formally derives a heterospin state composed of S = 1 for [Ru(II,II)2], S = 3/2 for [Ru(II,III)2](+), and S = ½ for TCNQ(•-), possibly causing intralayer ferrimagnetic spin ordering. Most of these types of compounds have an antiferromagnetic ground state because of the coupling of ferrimagnetically ordered layers in dipole antiferromagnetic interactions. However, 1 became a three-dimensional ferrimagnet with T(C) = 91 K because of the presence of interlayer ferromagnetic interactions.

A novel charge-disproportionation state with δ = 0.75 was observed in an electron-donor (D)/-acceptor (A) D(δ+)2A(2δ-) layered framework by chemically tuning the electron-donating affinity of D at the boundary between D(0.5+)2A(-) and D(+)2A(2-) phases, which was pressure-sensitive due to the formation of the D(+)2A(2-) oxidation state.

A series of paddlewheel diruthenium(ii, ii) complexes with various chlorine-substituted benzoate ligands (Cl-series) was synthesized as tetrahydrofuran (THF) adducts [Ru2(ClxPhCO2)4(THF)2]; where ClxPhCO2(-) = o-chlorobenzoate, ; m-chlorobenzoate, ; p-chlorobenzoate, ; 2,3-dichlorobenzoate, ; 2,4-dichlorobenzoate, ; 2,5-dichlorobenzoate, ; 2,6-dichlorobenzoate, ; 3,4-dichlorobenzoate, ; 3,5-dichlorobenzoate, ; 2,3,4-trichlorobenzoate, ; 2,3,5-trichlorobenzoate, ; 2,4,5-trichlorobenzoate, ; 3,4,5-trichlorobenzoate, ; 2,3,4,5-tetrachlorobenzoate, . This Cl-series and the previously synthesized F-series together with four new fluorine-substituted derivatives, [Ru2(FxPhCO2)4(THF)2] (where FxPhCO2(-) = 2,3-difluorobenzoate, ; 2,4-difluorobenzoate, ; 2,5-difluorobenzoate, ; 2,3,5-trifluorobenzoate, ), were experimentally characterized with respect to solid-state structure, magnetic properties and electrochemistry. By tuning the substituents of the benzoate ligands using chlorine or fluorine atoms, the redox potential (E1/2) for [Ru2(II,II)]/[Ru2(II,III)](+) varied over a wide range of potentials from -40 mV to 360 mV (vs. Ag/Ag(+) in THF). This was dependent on (i) the number of ortho-substituents, i.e. non-, mono- and di-o-substituted groups, with quasi-Hammett parameters for ortho-Cl and -F substitutions (σo = -0.272 and -0.217, respectively) and (ii) the general Hammett constants, σm and σp, for each group. The HOMO energy level calculated on the basis of the atomic coordinates of the solid-state structure was strongly affected by Cl- and F-substitutions as well as the redox potential in solution, which emphasizes the steric contribution of ortho-substituents in the energy level giving a deviation of EHOMO < 0.3 eV and <0.55 eV for the Cl- and F-series, respectively.

In a series of two-dimensional layered frameworks constructed by two electron-donor (D) and one electron-acceptor (A) units (a D2A framework), two-electron transferred systems with D(+)2A(2-) were first synthesized as [{Ru2(R-PhCO2)4}2(TCNQRx)]·n(solv) (R = o-CF3, Rx = H2 (1), R = o-CF3, Rx = Me2 (2), R = o-CF3, Rx = F4 (3), R = o-Me, TCNQRx = BTDA-TCNQ (4), R = p-Me, TCNQRx = BTDA-TCNQ (5), where TCNQ is 7,7,8,8-tetracyano-p-quinodimethane and BTDA-TCNQ is bis[1,2,5]dithiazolotetracyanoquinodimethane). The D(+)2A(2-) system was synthesized by assembling D/A combinations of paddlewheel-type [Ru2(II,II)(R-PhCO2)4] complexes and TCNQRx that possibly caused a large gap between the HOMO of D and the LUMO of A (ΔEH-L(DA)). All compounds were paramagnetic because of quasi-isolated [Ru2(II,III)](+) units with weakly antiferromagnetically coupled S = 3/2 spins via diamagnetic TCNQRx(2-) and/or through the interlayer space. The ionic states of these compounds were determined using the HOMO/LUMO energies and redox potentials of the D and A components in the ionization diagram for ΔEH-L(DA) vs ΔE1/2(DA) (= E1/2(D) - E1/2(A); E1/2 = first redox potential) as well as by previously reported data for the D2A and DA series of [Ru2]/TCNQ, DCNQI materials. The boundary between the one-electron and the two-electron transferred ionic regimes (1e-I and 2e-I, respectively) was not characterized. Therefore, another diagram for ΔEH-L(DA) vs |(2)E1/2(A) - (1)E1/2(A)|, where (2)E1/2(A) and (1)E1/2(A) are the second and first redox potentials of TCNQRx, respectively, was used because the 2e-I regime is dependent on on-site Coulomb repulsion (U = |(2)E1/2(A) - (1)E1/2(A)|) of TCNQRx. This explained the oxidation states of 1-5 and the relationship between ΔEH-L(DA) and U and allowed us to determine whether the ionic regime was 1e-I or 2e-I. These diagrams confirm that a charge-oriented choice of building units is possible even when designing covalently bonded D2A framework systems.

The gate-opening adsorption behavior of the one-dimensional chain compound [Ru2(4-Cl-2-OMePhCO2)4(phz)] (1; 4-Cl-2-OMePhCO2(-) = 4-chloro-o-anisate; phz = phenazine) for various gases (O2, NO, and CO2) was electronically monitored in situ by applying ac electric fields to pelletized samples attached to a cryostat, which was used to accurately control the temperature and gas pressure. The gate-opening and -closing transitions induced by gas adsorption/desorption, respectively, were accurately monitored by a sudden change in the real part of permittivity (ε'). The transition temperature (TGO) was also found to be dependent on the applied temperature and gas pressure according to the Clausius-Clapeyron equation. This behavior was also observed in the isostructural compound [Rh2(4-Cl-2-OMePhCO2)4(phz)] (2), which exhibited similar gate-opening adsorption properties, but was not detected in the nonporous gate-inactive compound [Ru2(o-OMePhCO2)4(phz)] (3). Furthermore, the imaginary part of permittivity (ε″) effectively captured the electronic perturbations of the samples induced by the introduced guest molecules. Only the introduction of NO resulted in the increase of the sample's electronic conductivity for 1 and 3, but not for 2. This behavior indicates that electronic host-guest interactions were present, albeit very weak, at the surface of sample 1 and 3, i.e., through grain boundaries of the sample, which resulted in perturbation of the conduction band of this material's framework. This technique involving the in situ application of ac electric fields is useful not only for rapidly monitoring gas sorption responses accompanied by gate-opening/-closing structural transitions but also potentially for the development of molecular framework materials as chemically driven electronic devices.

Three new sulfonated porous coordination polymers (PCPs)/metal-organic frameworks (MOFs) have been synthesized using solvothermal methods. These PCPs possess porous structures with non-coordinating sulfonic acid groups or sulfonate with dimethyl ammonium cations and exhibit high proton conductivity at a low humidity of 60% RH (relative humidity) at ambient temperature.

Carbon monoxide (CO) produced in many large-scale industrial oxidation processes is difficult to separate from nitrogen (N2), and afterward, CO is further oxidized to carbon dioxide. Here, we report a soft nanoporous crystalline material that selectively adsorbs CO with adaptable pores, and we present crystallographic evidence that CO molecules can coordinate with copper(II) ions. The unprecedented high selectivity was achieved by the synergetic effect of the local interaction between CO and accessible metal sites and a global transformation of the framework. This transformable crystalline material realized the separation of CO from mixtures with N2, a gas that is the most competitive to CO. The dynamic and efficient molecular trapping and releasing system is reminiscent of sophisticated biological systems such as heme proteins.

The design of porous materials that undergo selective adsorption of a specific molecule is a critical issue in research on porous coordination polymers or metal-organic frameworks. For the purpose of the selective capture of molecules possessing an electron-acceptor character such as nitric oxide (NO), one-dimensional chain compounds possessing a high donor character have been synthesized using 4-chloroanisate-bridged paddlewheel-type dimetal(II, II) complexes with M = Ru and Rh and phenazine (phz) as the chain linker: [M2(4-Cl-2-OMePhCO2)4(phz)]·n(CH2Cl2) (M = Ru, 1; Rh, 2). These compounds are isostructural and are composed of chains with a [-{M2}-phz-] repeating unit and CH2Cl2 occupying the void space between the chains. Compounds 1 and 2 change to a new phase (1-dry and 2-dry) upon evacuating the crystallization solvent (CH2Cl2) and almost lose their pores in the drying process: no void space in 1-dry and 31.8 Å(3), corresponding to 2.9% of the cell volume, in 2-dry. Nevertheless, the compounds show a unique gas accommodation ability. Accompanied by a structural transformation (i.e., the first gate-opening) at low pressures of <10 kPa, both compounds show a typical physisorption isotherm for O2 (90 K) and CO2 (195 K), with the adsorption amount of ca. 2-4 gas molecules per [M2] unit. In addition, the adsorption isotherm for NO (121 K) involves the first gate-opening followed by a second gate-opening anomaly at NO pressures of ≈52 kPa for 1-dry and ≈21 kPa for 2-dry. At the first gate-opening, the absorbed amount of NO is ca. 4 molecules per [M2] unit, and then it reaches 8.4 and 6.3 for 1-dry and 2-dry, respectively, at 95 kPa. Only the isotherm for NO exhibits hysteresis in the desorption process, and some of the NO molecules are trapped in pores even after evacuating at 121 K, although it recovers to the original dried sample on heating to room temperature. The adsorbed NO molecules accrue a significant electron donation from the host framework even in the [Rh2] derivative, indicating that such simple porous compounds with electron-donor characteristics are useful for the selective adsorption of NO.

On the basis of the concept that the design of a mixed valence system is a key route to create electronic conducting frameworks, we propose a unique idea to rationally produce mixed valency in an ionic donor/acceptor chain (i.e., D(+)A(-) chain). The doping of a redox-inert (insulator) dopant (P) into a D(+)A(-) chain in place of neutral D enables the creation of mixed valency A(0)/A(-) domains between P units: P-(D(+)A(-))nA(0)-P, where n is directly dependent on the dopant ratio, and charge transfer through the P units leads to electron transport along the framework. This hypothesis was experimentally demonstrated in an ionic DA chain synthesized from a redox-active paddlewheel [Ru2(II,II)] complex and TCNQ derivative by doping with a redox-inert [Rh2(II,II)] complex.

The reactions of paddlewheel-type diruthenium(II, II) complexes, [Ru2(II,II)(x-FPhCO2)4(THF)2] (x-FPhCO2(-) = x-fluorobenzoate with x- = o-, m-, p-), with 2,6-diaminopyridine (dapy) and 7-azaindole (azain) afford axially capped discrete compounds, [Ru2(II,II)(x-FPhCO2)4(dapy)2] (x = o-, 1; m-, 2; p-, 3) and [Ru2(II,II)(o-FPhCO2)4(azain)2] (4), respectively. In these compounds, intramolecular hydrogen bonds are observed between NH2 groups for 1-3 or imine NH groups for 4 and oxygen atoms of carboxylate groups. In addition, hydrogen bonds of NH2···F are also observed for 1 and 4 with an o-positioned F atom on benzoate. This coordination mode, i.e., a dual bonding mode with σ-bonding and hydrogen bonding, should assist ligand coordination to the axial position of the [Ru2] unit. The Ru-N bond distance in 1-4 is shorter than that observed in related compounds reported previously. In a similar fashion, reactions with planar M(II) dithiobiuret (dtb) complexes, [M(II)(dtb)2] (M(II) = Pd(II) and Pt(II)), were carried out. One-dimensional alternating chains, [{Ru2(II,II)(o-FPhCO2)4}{M(II)(dtb)2}] (M(II) = Pd(II), 5; Pt(II), 6), were obtained, in which the hydrogen-bonding modes of NH2···O and NH2···F are present, as expected. DFT calculations for the [M(II)(dtb)2] unit revealed that the LUMO of [M(II)(dtb)2] lies at -2.159 and -1.781 eV for M = Pd and Pt, respectively, which is much higher than HOMO energy at -4.184 eV calculated for [Ru2(II,II)(o-FPhCO2)(THF)2], proving that the respective units are essentially electronically isolated in the chains.

A porous one-dimensional coordination chain compound, [Ru(2)(p-F-PhCO(2))(4)(phz)] (; p-F-PhCO(2)(-) = para-fluorobenzoate; phz = phenazine) derived by drying its nitrobenzene-solvated compound, specifically adsorbs CO(2) at 195 K in a stepwise sorption manner.