This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2020 New J. Chem., 2020, 44, 10317--10325 | 10317 Cite this: New J. Chem., 2020, 44, 10317 Dinuclear complexes of Mn, Co, Zn and Cd assembled with 1,4-cyclohexanedicarboxylate: synthesis, crystal structures and acetonitrile fluorescence sensing properties† Luis D. Rosales-Va ´ zquez, a Diego Martı ´ nez-Otero, b Vı ´ ctor Sa ´ nchez-Mendieta, * b Jonathan Jaramillo-Garcı ´ a, b Antonio Te ´ llez-Lo ´ pez, b Roberto Escudero, c Francisco Morales, c Josue Valdes-Garcı ´ a a and Alejandro Dorazco-Gonza ´ lez * a Four dinuclear complexes: [Mn 2 (H 2 O) 2 (chdc) 2 (bipy) 2 ], 1; [Co 2 (H 2 O) 2 (chdc) 2 (bipy) 2 ]H 2 O, 2; [Zn 2 (H 2 O) 2 (chdc) 2 - (bipy) 2 ]H 2 O, 3; and [Cd 2 (H 2 O) 2 (chdc) 2 (bipy) 2 ]H 2 O, 4; chdc = e,a-cis-1,4,cyclohexanedicarboxylate and bipy = 2,2 0 -bipyridine, were attained as single crystals under ambient conditions. Crystallographic studies show that complexes 1, 2 and 3 are isostructural and crystallize in the monoclinic system with the P2 1 /c space group. The metal centers in these complexes are hexa-coordinated with a distorted octahedral coordination sphere. Complex 4 crystallizes in the triclinic system with the P % 1 space group; in this compound, the metal centers are hepta-coordinated and their coordination sphere is distorted-capped trigonal prismatic. Magnetic property measurements reveal that complexes 1 and 2 exhibit weak antiferromagnetic ordering. Complex 4 displays solid-state blue emission properties and a highly sensitive response to acetonitrile in water based on turn-on fluorescence with a low detection limit of 1.1 mM and selectivity over common polar organic solvents. 1. Introduction Dinuclear and polynuclear coordination complexes have been synthesized extensively throughout, at least, the past sixty years, primarily as a subject of chemical structure studies and its relationship to properties, such as, magnetism, optics, electronics, etc. 1 However, in the last three decades, these types of compounds have been pursued further as functional materials, with novel applications according to their chemical, morphological and textural properties, among others. These applications range from sensing 2 and molecular recognition 3 to catalysis 4 and anticancer. 5 Thus, nowadays, the search for new coordination complexes with fascinating structures but, most importantly, with relevant properties and applications continues to be a hot topic. Among the possible properties that can be incorporated into a coordi- nation compound, luminescence is a very treasured one, since it provides the possibility of using the complex as a fluorescent probe for chemosensing hazardous substances, 6 amid other technological applications. Dinuclear complexes assembled with 1,4-cyclohexanedicarboxylate are, to some extent, rare. To our knowledge, dinuclear complexes of Cu, 7 Mo, 8 Sn, 9 Pb, 10 Eu 11 and Tb 11 have been reported. In most of these complexes the chdc bridging ligand assumes the most common e,a-cis conformation of the carboxylate moieties. The e,e-trans conformation of the chdc ligand is somewhat uncommon, it has been reported only in coordination polymers made with Fe, 12 La, 13 Nd, 14 and Sm 14 and in our work with a 3-D Cd polymer. 15 The rarest conformation is a,a-trans, which has been found only once in a Sm coordination polymer, in combination with the e,e-trans conformation. 16 In most of the literature related to dinuclear complexes using the chdc bridging ligand, structural studies and solid-state fluorescence properties have mainly been investigated, but no further potential applications have been explored. On the other hand, the development of fluorescent sensors based on d 10 metal complexes that can detect small-molecule organic solvents with chemical and environmental relevance, a Instituto de Quı ´mica, Universidad Nacional Auto´noma de Me ´xico, Circuito Exterior, Ciudad Universitaria, Ciudad de Me ´xico, 04510, Mexico. E-mail: adg@unam.mx b Centro Conjunto de Investigacio´n en Quı ´mica Sustentable UAEM-UNAM, Carretera Toluca-Ixtlahuaca Km. 14.5, Tlachaloya, Toluca, Estado de Me ´xico, 50200, Mexico. E-mail: vsanchezm@uaemex.mx c Instituto de Investigaciones en Materiales, Universidad Nacional Auto´noma de Me ´xico, Apartado Postal 70-360, Ciudad de Me ´xico, 04510, Mexico † Electronic supplementary information (ESI) available: CCDC 1907858–1907861 (1–4). For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/d0nj01410a Received 22nd March 2020, Accepted 17th May 2020 DOI: 10.1039/d0nj01410a rsc.li/njc NJC PAPER Published on 18 May 2020. Downloaded by FAC DE QUIMICA on 11/2/2020 10:23:34 PM. View Article Online View Journal | View Issue