A novel Cu(I)-based two-dimensional (2D, 4 4 net) metal−organic framework (MOF) [Cu(L)(I)] 2n •2nDMF• nMeCN (1); L = 4′-(4-methoxyphenyl)-4,2′:6′,4″-terpyridine; DMF = N,N-dimethylformamide, MeCN = acetonitrile) has been synthesized and found to behave as a colorimetric detector for the widest variety of small molecules such as different solvents, halobenzenes, N-heterocycles, amine, and nitroaromatic explosives all in vapor phase through a single crystal to single crystal (SCSC) transformation. The 2D 4 4 nets are interdigitated with each other to form a supramolecular 3D MOF having 1D pore. The interdigitated layers are stabilized by π•••π interactions and CH•••π interactions and provide extreme stability up to 380 °C. Interestingly, all guest exchange and encapsulation processes are reversible without loss of structural integrity. Positions of the guest molecules in the host−guest complex have been identified from the crystal structure and found to involve weak interactions with the framework. Notably, this is the first time for a report of any material which encapsulates such a large number of small molecules in the vapor phase from different chemical classes in SCSC fashion with visible color changes. Tests confirm the selectivity toward most polar molecule in a class. In the presence of guest molecules, the MOF exhibits a blue shift in fluorescence emission spectra and the extent of the blue shift is appreciably high. It also shows high selectivity toward diethylamine (dea) among N-heterocycles, amine, and highly explosive trinitrophenol (TNP) among nitroaromatic explosives as revealed from concurrent luminescence quenching in solution. Finally, the MOF represents one of the best hosts reported so far having extreme stability and selectivity and meets the benchmark of reversibility for material applications.

Two new ternary materials NaGaS 2 (1) and the Fedoped phase of NaGaS 2 , NaFe 0.135 Ga 0.865 S 2 (2), have been synthesized by employing polysulfide flux. Single crystal XRD analyses of 1 and 2 show that the structure is built up of adamantane-like Ga 4 S 10 super tetrahedral fundamental building units. These admantane-like units are connected through their corners to form [GaS 2 ] ∞ − layers that are stacked one over the other with Na ions residing in between the layers to balance the charge. Both the materials have the remarkable ability to absorb atmospheric water molecules and moisture from undried solvents as verified by TG analysis and FT-IR and XPS studies. The process of water absorption leads to stable distinct material) with restacked layers different from original crystal structure. This structural transformation is reversible as the transformed structures 1•H 2 O and 2•H 2 O can be returned to their original structures 1 and 2, respectively, upon heating. DFT calculation study reveals that a spontaneous exergonic hydration reaction takes place as outlined in NaGaS 2 + H 2 O → NaGaS 2 •H 2 O with the energy release, ΔE of −73.9 kJ mol −1 . DFT calculation predicts an increase in the unit cell parameters of b and c directions and shrinkage along the a direction of hydrated phase 1•H 2 O with an overall volume increase of 36.6%. Structural transformation affects their physical properties as the pristine compound 1 possess Na + ion conductivity of 2.88 × 10 −7 S cm −1 at 22 °C, whereas the hydrated compound 1•H 2 O displays ∼40 times increased ion conductivity of 1.25 × 10 −5 S cm −1 at the same temperature. DRS studies show very similar optical band gaps of ∼4 eV for compounds 1 and 1•H 2 O, respectively, in reasonable agreement with the DFT(HSE) band gap estimation but more than 1 eV above the DFT(PBE)-predicted band gaps of ∼2.4 eV. A sorption study indicates selective adsorption of water over MeOH, EtOH, and CH 3 CN with a maximum water uptake of 2.6 H 2 O per formula unit at P/P 0 = 0.9. A Karl Fischer titration study shows that NaGaS 2 (1) is certainly capable of adsorbing water from wet methanol and can be useful as a fast desiccating agent.

Two 2D coordination polymers have been synthesized by employing V-shaped flexible terpyridine-based ligand L [L = 4′-(4-methoxyphenyl)-4,2′:6′,4′′-terpyridine] as linker and M II (M = Co II , Fe II ) as nodes. Structural analysis of both complexes revealed the formation of a rare [4+4] metallocyclic unit. The extension of these cyclic units into two dimensions gives rise to an interdigitated 2D sheet structure in which the methoxy group of the ligand is oriented above and below the sheet IntroductionOver the past few decades, coordination polymers (CPs) have attracted extensive research interest owing to the variety of their architectures and intriguing topologies [1] as well as potential applications. [2] Apart from their structural role in supporting solid-state architectures, the metal ions in CPs are the source of some useful physical properties, for example, the blocking of magnetization, and molecules having such properties are known as single-molecule magnets (SMMs). [3,4] SMMs are known for their potential applications in high-density data storage, quantum computing, and molecular spintronics. [3] Recently, there has been particular interest in molecular systems with only one spin carrier, large magnetic anisotropy, no intermetallic interactions, and properties similar to SMMs called single-ion magnets (SIMs). The most interesting feature of SIMs [5] is the possibility of tuning their magnetic anisotropy through the regulation of the coordination number and ligand field. In parallel with the extensive study of lanthanide-based SIMs, [5] significant effort has also been devoted to the research of transition-metal-based SIMs. [6][7][8] A common feature of all the reported transition-metal-based SIMs is the low coordination number of the metal centers, for which the single-ion anisotropy is enhanced due to unrestricted orbital angular momentum by limiting the coordination number of the metal ion. [9] Among 3d SIMs, Co II -based complexes are the most interesting because of their non-integer spin ground state, [10] which reduces the probability of quantum tunneling of magnetization (QTM). [11] Recently, a few octahedral Co II complexes have been [a] for their helpful scientific discussions.

Flexible and dynamic Cu I metal−organic framework [Cu(I)-MOF (1)] with well-defined nanoporous channel built with flexible terpyridine ligand offers a scaffold for the inclusion of different classes of guest molecules through a single-crystal-tosingle-crystal (SCSC) transformation in the vapor phase at ambient conditions with visual color change. Thus, Cu(I)-MOF (1) offers a potential platform for molecular recognition and undergoes guestresponsive structural dynamism that can be triggered by interfacial interactions. Despite having the stable conformation of the rotational isomers, it selectively encapsulates the less stable conformation (eclipsed and gauche) into its cavity from their vapor phases in the SCSC process. All of the guest-exchanged processes are reversible. It shows selectivity toward less polar guest in a class. The intermediate of all of the guest-exchanged processes appeared as a black material (H 2 O@Cu(I)-MOF) (1z) prior to the encapsulation of each guest that happens through the SCSC manner followed by encapsulation of the guests replacing H 2 O in situ at ambient conditions through SCSC transformation. This confirms that the process is a two-step process leading to a common intermediate. The MOF loses its luminescence behavior with H 2 O removing lattice solvents in situ and appears as a black material, and it regains its luminescence property with the guests replacing H 2 O. Thus, the MOF displays both luminescence "turn-off" and "turn-on" before and after incorporation of the guests, respectively, leading to a common turn-off mechanism. A fluorescence titration experiment shows selectivity toward aniline among benzene and its derivatives.

A novel octadecanuclear copper pyrazolate-phosphonate nanocage with a bowl-shaped arrangement of the copper(II) centers in the asymmetric unit is reported. Characterization of intermediates in both solid and solution states aids to propose the mechanism of such a giant aggregation. Magnetic studies affirm the presence of antiferromagnetic interactions between the adjacent copper(II) centers. Extensive supramolecular interactions result in a framework structure.