Cadmium–1,4-cyclohexanedicarboxylato coordination polymers bearing different di-alkyl-2,2′-bipyridines: syntheses, crystal structures and photoluminescence studies

Abstract

Four coordination polymers have been synthesized using self-assembly solution reactions under ambient conditions, reacting Cd(ii) ions with 1,4-cyclohexanedicarboxylic acid in the presence of different 2,2'-bipyridine co-ligands: {[Cd(HO)(e,a-cis-1,4-chdc)(2,2'-bpy)]·HO} (1); [Cd(HO)(e,a-cis-1,4-chdc)(4,4'-dmb)] (2); {[Cd(e,a-cis-1,4-chdc)(5,5'-dmb)]·HO·CHOH} (3) and {[Cd(e,e-trans-1,4-chdc)(4,4'-dtbb)]·CHOH} (4), where 1,4-chdc = 1,4-cyclohexanedicarboxylato, 2,2'-bpy = 2,2'-bipyridine, 4,4'-dmb = 4,4'-dimethyl-2,2'-bipyridine, 5,5'-dmb = 5,5'-dimethyl-2,2'-bipyridine and 4,4'-dtbb = 4,4'-di-tert-butyl-2,2'-bipyridine. Crystallographic studies show that compound 1 has a 1D structure propagating along the crystallographic b-axis; the Cd ion in 1 is six-coordinated with a distorted-octahedral coordination sphere. Compound 2 has two crystallographic different Cd ions and both are six-coordinated with a distorted-octahedral coordination sphere. Compound 3 exhibits a seven-coordinated Cd ion having a distinctive distorted-monocapped trigonal prismatic geometry. In compound 4, the Cd ion is also seven-coordinated in a distorted monocapped octahedral geometry. Compounds 2, 3 and 4 possess rhombic-shaped dinuclear units (CdO) as nodes to generate larger cycles made up of four dinuclear units, a Cd motif, bridged by four 1,4-chdc ligands, accomplishing, thus, 2D structures. Remarkably, in compound 4 the 1,4-chdc ligand conformation changes to the equatorial, equatorial trans, unlike the other compounds where the bridging ligand conformation is the more typical equatorial, axial cis. The solid state luminescence properties of 1-4 were investigated; polymers 3 and 4 exhibited a strong blue emission (λ = 410-414 nm) compared to 1 and 2; structure-related photoluminescence is attributed to the degree of hydration of the compounds. Furthermore, Cd-polymer 3 suspended in acetone allows the fluorescence selective sensing of acetonitrile over common organic solvents such as alcohols and DMF, based on turn-on fluorescence intensity with a limit of 53 μmol L.

Structure of a Luminescent MOF-2 Derivative with a Core of Zn(II)-Terephthalate-Isoquinoline and Its Application in Sensing of Xylenes

“…The CPMAS 13 C NMR experiment was recorded with a Bruker Advance II 300 spectrometer (Bruker BioSpin GmbH, Rheinstetten, Germany) (operating at 75 MHz for 13 C) on a 4 mm rotor double resonance. The CPMAS experiment was recorded with a contact time of 2 ms and a delay of 5 s at a 7 kHz spinning rate at ambient temperature.…”

“…Crystals 2020, 10, x FOR PEER REVIEW 7 of 13 Figure 6. 13 C CPMAS NMR spectrum for 1 and numbering scheme of the building unit. Regions with The IR spectrum shows the common bands expected for coordinated carboxylate ligands to atoms Zn(II) along with the corresponding bands to isoquinoline.…”

“…There is a growing interest in the development of photoluminescent metal-organic materials (MOMs) [1][2][3][4], where the color emission upon excitation is a significant feature of these materials that has been recently used in several applications such as emitting devices/materials [5,6], optical sensing of vapor phase analytes [3,7], detection of ions [8,9], bioanalytes [10], explosives [11,12], and detection of volatile organic solvents (VOCs) [8,13,14]. Most known MOMs-based chemosensors for organic solvents act in a "turn-off" response where the fluorescence intensity of the compound is quenched upon addition of the analyte [7,15,16].…”

“…Taking this into account, this work is based on the idea that a new metal-organic compound with photoluminescence can be achieved in a single step and in high yield by the straightforward combination of Zn(II) ions with 1,4-benzenedicarboxylic acid and a commercial benzopyridine ligand, which can act as a luminescent unit when coordinated to the metal center. X-ray crystal structures, thermogravimetry, CPMAS 13 C-NMR spectroscopy, morphological studies with SEM-EDS, and fluorescent sensing properties obtained for a novel blue luminescent 2D MOF based on Zn-terephthalate with an isoquinoline core are herein discussed.…”

Syntheses and Crystal Structures of Mn(II), Ni(II) and Cu(II) Coordination Compounds Assembled by Maleato and Dimethyl-2,2′-bipyridines

“…Carboxylates used as ion metal linkers can afford 1D, 2D or 3D polymers depending mainly on their coordination modes and, of course, on the metal ion involved [7,8]. Therefore, in our continuing investigations on novel transition metal coordination complexes and polymers with interesting luminescent and magnetic properties [9][10][11], we are now involved in the generation of synthons bearing metal ions and carboxylate ligands, which eventually can function as linkers in the formation of heteronuclear coordination polymers. Maleic acid, as maleate, has been employed previously as bridging ligand in the synthesis of coordination polymers [12,13].…”