Reticular synthesis, topological studies and physicochemical properties of a 3D manganese(II) coordination network [Mn3(BTC)2(DMSO)4]n European Journal of Chemistry 10 (2) (2019) 180-188 European Journal of Chemistry View Journal Online View Article Online Reticular synthesis, topological studies and physicochemical properties of a 3D manganese(II) coordination network [Mn3(BTC)2(DMSO)4]n Leonã da Silva Flores 1, Roselia Ives Rosa 1, Jefferson da Silva Martins 3, Roberto Rosas Pinho 3, Renata Diniz 2 and Charlane Cimini Corrêa 1,* 1 Department of Chemistry, Federal University of Juiz de Fora, Juiz de Fora, 36036-900, Brazil leonansf@hotmail.com (L.S.F.), roseliaives@hotmail.com (R.I.R.), charlane.cimini@ufjf.edu.br (C.C.C.) 2 Department of Chemistry, Federal University of Minas Gerais, Belo Horizonte, 31270-901, Brazil dinizr@gmail.com (R.D.) 3 Department of Physics, Federal University of Juiz de Fora, Juiz de Fora, 36036-900, Brazil jeffersonsilvamartins@gmail.com (J.S.M.), rrpinho1959@gmail.com (R.R.P.) * Corresponding author at: Department of Chemistry, Federal University of Juiz de Fora, Juiz de Fora, 36036-900, Brazil. Tel: +55.32.21023310 Fax: +55.32.21023314 e-mail: charlane.cimini@ufjf.edu.br (C.C. Corrêa). 10.5155/eurjchem.10.2.180-188.1882 Received: 16 April 2019 Received in revised form: 20 May 2019 Accepted: 28 May 2019 Published online: 30 June 2019 Printed: 30 June 2019 In order to build a metal-organic framework with mixed ligands (acid-acid), a 3D coordination network based on manganese metal center was obtained [Mn3(BTC)2(DMSO)4]n; where BTC = Benzene-1,3,5-tricarboxylic acid and DMSO = Dimethylsulfoxide. The crystal structure was determined by single crystal X-ray diffraction, showing the assembly of a tridimensional 3,6-connected non-entangled polymeric network, with RTL topology. The secondary building unit (SBU) acts as a node of the 3-periodic expansion and involves carboxylate- and oxo-bridged metals. The DMSO employed in the synthesis is chemically involved in the coordination as a µ2-O bridge between distinct manganese metal centers. The structural characterization of the material was supported by spectroscopic (infrared absorption and Raman scattering), thermal (TG, DTG, and DTA) and elemental analysis. Manganese Trimesic acid Reticular synthesis Coordination polymer Coordination network Secondary building unit Cite this: Eur. J. Chem. 2019, 10(2), 180-188 Journal website: www.eurjchem.com 1. Introduction Coordination networks (CNs) are a subclass of coordination polymers (CPs) able to form loops, cross-links or spiro-links that extend periodically in 1D, 2D or 3D. Metal- organic frameworks (MOFs) are a subclass of CNs that are capable of hosting guests in their vacancies, either through bonds or interactions [1,2]. This hierarchical taxonomy, in addition to topological studies of CPs, are strongly recom- mended by the International Union of Pure and Applied Chemistry (IUPAC); as it allows a complete description of the assembled system [3]. In this way, the design of MOFs may be an interdisciplinary challenge, involving principles of Reticular Chemistry (RC) and the techniques or experiments that will produce materials with specific topologies, pore size, and functionalities [4-6] Generally, reticular synthesis of MOFs is based on oxo-metallic connectors or secondary building units (SBUs - polynuclear groups, geometrically defined), in which the components are strongly bound and will drive the expansion [7,8]. Some basic knowledge of RC contemplates a series of principles, such as the Geometric Design Principle, which considers that most structures will be determined by the simplest geometric form. This principle can be demonstrated by the synthesis of edge- transitive nets (default nets) [9] or by isoreticular materials, with the same topology [10]. Moreover, the Deconstruction Principle allows the reduction of the structural complexity of an underlying net with a fundamental topology. If there is a wide variety of SBUs and polytopic ligands, these can be simplified as geometric forms (polygons, polyhedra, rods, etc.) determined by essential points for expansion of the net: the points of extension [11]. In addition, the Minimal Transitivity Principle is based upon the observation that underlying nets, generally, tend to present minimal transitivity [12]. The transitivity of a net gain in understanding the structure even in more complex networks. Minimal transitivity will be related to the simplest structural attribution. ABSTRACT RESEARCH ARTICLE KEYWORDS European Journal of Chemistry ISSN 2153-2249 (Print) / ISSN 2153-2257 (Online) – Copyright © 2019 The Authors – Atlanta Publishing House LLC – Printed in the USA. This work is published and licensed by Atlanta Publishing House LLC – CC BY NC – Some Rights Reserved. http://dx.doi.org/10.5155/eurjchem.10.2.180-188.1882 http://dx.doi.org/10.5155/eurjchem.10.2.180-188.1882 https://crossmark.crossref.org/dialog/?doi=10.5155/eurjchem.10.2.180-188.1882&domain=pdf&date_stamp=2019-06-30 http://www.eurjchem.com/ http://dx.doi.org/10.5155/eurjchem.10.2.180-188.1882 mailto:leonansf@hotmail.com mailto:roseliaives@hotmail.com mailto:charlane.cimini@ufjf.edu.br mailto:dinizr@gmail.com mailto:jeffersonsilvamartins@gmail.com mailto:rrpinho1959@gmail.com mailto:charlane.cimini@ufjf.edu.br http://www.eurjchem.com/ https://crossmark.crossref.org/dialog/?doi=10.5155/eurjchem.10.2.180-188.1882&domain=pdf&date_stamp=2019-06-30� Flores et al. / European Journal of Chemistry 10 (2) (2019) 180-188 181 Table 1. Crystal data and structure refinement for [Mn3(BTC)2(DMSO)4]n. Parameters [Mn3(BTC)2(DMSO)4]n Empirical formula C26H30S4O16Mn3 Formula weight 891.56 Temperature (K) 293.11(10) Crystal system Monoclinic Space group P21/c a, (Å) 10.2683(2) b, (Å) 10.3933(2) c, (Å) 16.6366(3) β (°) 95.189(2) Volume (Å3) 1768.21(6) Z 2 ρcalc (g/cm3) 1.675 μ (mm-1) 1.360 F(000) 906.0 Crystal size (mm3) 0.25 × 0.07 × 0.04 Radiation MoKα (λ = 0.71073) The 2Θ range for data collection (°) 3.3 to 27.9 Index ranges -13 ≤ h ≤ 13, -13 ≤ k ≤ 13, -21 ≤ l ≤ 21 Reflections measured 37629 Independent reflections 4178 [Rint = 0.041] Restraints/parameters 0/227 Goodness-of-fit on F2 1.04 Final R indexes [I≥2σ (I)] R1 = 0.040, wR2 = 0.0975 Final R indexes [all data] R1 = 0.0484, wR2 = 0.1027 Largest diff. peak/hole (e Å-3) 1.92 /-0.78 Considering all the principles and approximations related to RC, it may be said that the strategies to build MOFs are not trivial and demand chemical knowledge. In this sense, benzene-1,3,5-tricarboxylic acid or trimesic acid has been employed largely as a tritopic ligand to build MOFs, principally, due to its high coordination power [13,14]. Diversity of structures and functionalities has been reported in the literature [15,16]. Although a large number of structures based on trimesic acid have been reported, there is a challenge to build MOFs based on trimesic acid in addition to another ligand (mixed-ligand-MOFs) [17-19]. This illustrates the importance of proposing new strategies of synthesis and the comprehension of the assembly of these systems. Therefore, the objective of this work is to present the reticular synthesis, characterization and structural description of a novel 3D Mn(II)-coordination network, built from trimesic acid and DMSO which exhibits interesting structural and topological attributes. 2. Experimental All chemicals were reagent grade, obtained from commercial sources, and used without further purification. Benzene-1,3,5-tricarboxylic acid/trimesic acid (BTC), pentanedioic acid/glutaric acid (GLU), manganese acetate Mn(CH3COO)2·4H2O, and the solvent dimethylsulfoxide (DMSO) were purchased from Sigma-Aldrich. The synthesis was carried out by slow diffusion using a 1:1:1 stoichiometry, at room temperature. In a test tube, Mn(CH3COO)2·4H2O (0.3 mmol, 0.0519 g) was added to a mixture of 1.5 mL of deionized water and 0.5 mL of DMSO. A mixture of DMSO (3.0 mL) and deionized water (1.0 mL) was carefully added, forming a thin layer. Finally, a solution of BTC (0.3 mmol, 0.0396 g) and GLU (0.3 mmol, 0.0519 g) ligands in DMSO (4.0 mL), after having its pH modified by the addition of 1.5 mL of NaOH 1.0 M and was carefully added over the layers. The system was then maintained undisturbed at room temperature. After one week, single crystals were observed on the wall of the tube. The obtained solid was filtered off, washed with cold ethanol and air dried at room temperature. The initial purpose of this synthesis was to build a MOF with mixed ligands (BTC/GLU). Catena-[bis(µ5-benzene-1, 3, 5-tricarboxylato)-bis(µ2-dimet hylsulfoxide)-bis(dimethylsulfoxide)-tri-manganese]: Color: Colorless. Yield: 68 %. FT-IR (KBr, ν, cm-1): 3010 (νCHar), 2362 (νCH-sp3DMSO), 2331 (νCH-sp3DMSO), 1623 (νCOO-as), 1587 (νCC), 1548 (νCOO-as), 1441 (νCOO-s), 1378 (νCOO-s), 1001 (νSO), 577 (δCOµ-DMSO), 541 (νMnO), 386 (β-MnO2). RAMAN (ν, cm-1): 3007 (νCHar), 1612 (νCOO-as), 1602 (νCC), 1550 (νCOO- as), 1454 (νCOO-s), 1377 (νCOO-s), 1007(νSO), 386 (β-MnO2). Anal. calcd. for Mn3C26H30O16S4: C, 34.9; H, 3.3 %. Found: C, 32.1; H, 4.9%. 2.1. Instrumentation Single crystal X-ray diffraction (SCXRD) measurement was carried out at room temperature, using a Supernova Agilent diffractometer, with Mo Kα (λ = 0.71073 Å). The crystal structure was solved and refined by SHELXT 14/5 and SHELXL 18/1 programs [20-22] and the multiscan absorption correction was applied. Data collection, reduction, and cell refinement were executed by Crysallis RED, Oxford diffraction Ltd. Version 1.171.32.38 and are presented in Table 1. Hydrogen atoms were located in a difference Fourier map and were added in idealized positions and then refined according to the riding-model approach, with C-H = 0.95 Å and with Uiso(H) = 1.2Ueq(C) [23,24]. All non-hydrogen atoms were refined anisotropically. The representations of the crystal structure were drawn by Mercury 4.1.0 and ORTEP3 programs for Windows [25-28]. The topological analysis of the network was performed by ToposPro package [29,30]. The natural tiling was drawn using Systre and 3dt programs [31]. Powder X-ray diffraction experiment was carried out using a Bruker diffractometer (D8 Advance), with monochromatic Cu-Kα radiation source, in the range from 5 to 55° (2θ) and with the steps of 0.02 ° at 40 kV and 40 mA. The infrared absorption (IR) spectra were collected using KBr disks in the range of 4000-400 cm-1 on a Bruker Alpha FTIR spectrometer. The Raman (R) spectrum was obtained on a Bruker RFS 100 equipment with an Nd:YAG laser operating at 1064 nm. Thermal analysis (TG/DTG/DTA) data were obtained through measurements on a Shimadzu DSC-60 thermal analyser, using a Shimadzu TGA-60 thermo-balance. Approxi- mately 5.7 mg of the sample was placed in an alumina crucible and heated in N2 atmosphere at 10 °C/min from 18 to 600 °C. Elemental analysis (CHN) was measured on a Perkin Elmer model 2400. Mass spectrometry matrix-assisted laser desorption / ionization (MALDI) experiments were performed 2019 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.10.2.180-188.1882 182 Flores et al. / European Journal of Chemistry 10 (2) (2019) 180-188 Table 2. Selected geometric parameters of the crystal structure of [Mn3(BTC)2(DMSO)4]n *. Bond distances (Å) Mn2-O2 iii 2.1079 (19) S1-O7 1.525 (2) Mn2-O2 vi 2.1079 (19) S1-C11 1.771 (5) Mn2-O3 2.1203 (19) S1-C10 1.791 (5) Mn2-O3 v 2.1203 (19) S2-O8 1.505 (3) Mn2-O7 iii 2.348 (2) S2-C13 1.758 (5) Mn2-O7 v 2.348 (2) S2-C12 1.782 (5) Mn1-O1 2.109 (2) O3-C8 1.253 (3) Mn1-O4 iv 2.142 (2) O4-C8 1.248 (4) Mn1-O8 2.168 (2) O1-C1 1.258 (3) Mn1-O7 2.218 (19) O2-C1 1.249 (3) Mn1-O5 ii 2.228 (2) O6-C9 1.256 (4) Mn1-O6 ii 2.306 (2) O5-C9 1.266 (3) Bond angles / ° O2iii-Mn2-O2 vi 180.00 (10) O1-Mn1-O4iv 91.91 (9) O2iii-Mn2-O3 90.38 (8) O1-Mn1-O8 91.30 (10) O2vi-Mn2-O3 89.62 (8) O4iv-Mn1-O8 176.70 (10) O2iii-Mn2-O3 v 89.62 (8) O1-Mn1-O7 101.33 (8) O2vi-Mn2-O3 v 90.38 (8) O4iv-Mn1-O7 89.10 (9) O3-Mn2-O3 v 180.0 O8-Mn1-O7 89.54 (9) O2iii-Mn2-O7 iii 90.93 (8) O1-Mn1-O5ii 158.12 (8) O2vi-Mn2-O7 iii 89.07 (8) O4iv-Mn1-O5ii 86.33 (8) O3-Mn2-O7 iii 84.19 (8) O8-Mn1-O5ii 90.96 (9) O3v-Mn2-O7 iii 95.81 (8) O7-Mn1-O5ii 100.44 (7) O2iii-Mn2-O7 v 89.07 (8) O1-Mn1-O6ii 99.95 (8) O2vi-Mn2-O7 v 90.93 (8) O4iv-Mn1-O6ii 88.09 (9) O3-Mn2-O7 v 95.81 (8) O8-Mn1-O6ii 92.08 (9) O3v-Mn2-O7 v 84.19 (7) O7-Mn1-O6ii 158.61 (7) O7iii-Mn2-O7 v 180.00 (8) O5ii-Mn1-O6ii 58.22 (7) Symmetry code: (i) x-1, y, z; (ii) x+1, y, z; (iii) –x-1, y-1/2, -z+3/2; (iv) -x+1, y+1/2, -z+3/2; (v) -x+1, -y+1, -z+2, (vi) x, -y+3/2, z+1/2. using a pulsed nitrogen ultraviolet laser (λ = 337 nm) of an AXIMA Performance MALDI-TOF MS (Shimadzu Biotech). The time-of-flight mass spectrometer operated in a high vacuum chamber with a base pressure of about 1.0×10−7 mbar. The calibration utilized the alpha-cyano-4-hydroxycinnamic acid (CHCA) dissolved in water (50:50 v:v) milli-Q quality/ acetonitrile with 0.1 % TFA (trifluoroacetic acid) at a concentration of about 5×10−2 mol/L. For MALDI-TOF MS measurements, samples were suspended in DMSO (20 μL) and the final suspension was added to 20 μL of the matrix solution. 0.5 μL of this mixture was deposited on the stainless steel multiprobe and allowed to dry before introduction into the mass spectrometer. The instrument was set in the high- resolution, positive reflector ion mode and scans were taken from 100 to 400 m/z. 3. Results and discussion 3.1. Crystal structure description All crystallographic data for the compound are exhibited in Table 1 and all geometric parameters, such as bond distances and angles, are summarized in Table 2. Coordination polymer [Mn3(BTC)2(DMSO)4]n crystallizes in the monoclinic crystal system, with the centrosymmetric space group P21/c, with BTC ligand totally deprotonated and coordinated to the Mn(II) and expanding the polymeric structure. Figure 1a represents the coordination environment of a fragment of the crystal structure of compound [Mn3(BTC)2 (DMSO)4]n. The asymmetric unit involves two distinct metal centers, Mn1 and Mn2, crystallographically independent and the analysis of geometric parameters suggests that both of them adopt a distorted octahedral geometry, in which Mn1 is highly distorted. The BTC ligand is hexadentate as a µ5-ligand, wherein the carboxylate group O5-C9-O6 coordinates to Mn1i in a chelating η2 mode. The carboxylate group C1-O1-O2 bridges Mn1 and Mn2iv in a µ2-η1:η1 mode (with a syn-syn conformation) and the carboxylate group O3-C8-O4 is coordinated to Mn2 in the same way. Two DMSO ligands, crystallographically independent, (O7-DSMO and O8-DMSO) are coordinated to Mn1. Only O7-DMSO is brides (µ2-O) the two metal centers Mn2 and Mn1iii. Figure 1b represents the polyhedrons Mn1O6 and Mn2O6, in which the distorted octahedral geometry is promoted by the coordination environment surrounding Mn1 and Mn2 metal centers: four oxygen atoms from the BTC ligand (Mn1-O1, Mn1-O4, Mn1-O5, Mn1-O6) and two oxygen atoms (Mn1-O7 and Mn1-O8) from the DMSO ligand, displaying an average Mn-O distance of 2.194(9) Å. The largest angular deformation involves the Mn1 metal center and is attributed to the chelating ring formation Mn1-O5ii-C9ii-O6ii. This exhibits the most acute angle, 58.22 (7) °, and the largest Mn-O bond distance as Mn2-O7iii and Mn2- O7v, 2.348 (2) Å. The secondary building unit (SBU) appears as an hourglass trinuclear unit that expands periodically and is represented in Figure 1c, wherein the manganese metal centers Mn1···Mn2 are separated by 3.632 Å. It is interesting to notice that other coordination compounds presenting this type of linear trinuclear unit exhibit a variable value of the Mn(II)···Mn(II) distance: ranging from 3.213, 3.207, 3.232 to 3.223 Å [32]; and from 3.370 and 3.715 Å [33] to 3.593 Å [34]. Another reported SBU assembly involves a different array where the non-linear unit forms a trinuclear prism with a comparable Mn(II)···Mn(II) distance of 3.572 Å [35]. The tridimensional expansion of the coordination network is shown in Figure 1d, in which the vacancies of the net are growing along the a axe, occupied by DMSO ligands (represented as spacefill). The dashed region emphasizes the SBU. It should be noted that the carboxylate involved in the oxo-bridge can also assemble an infinite linear oxo-bridging in SBUs of coordination compounds, with diverse dimensiona- lities. A 1D coordination compound with magnetic properties and thermal behavior based on pivalate ligand and the acetate counter-ion was assembled from infinite oxo-bridge-SBU expansion [36]. On the other hand, an important and already known 3D metal-organic framework, MIL-53, possesses a similar infinite SBU composed by infinite oxo-bridge involving terephthalate and water ligands expanding tridimensionally [37]. Comparison of the compound’s SBU suggests that the one-directional expansion of the SBU is stopped by chelation with Mn1 metal center. The manganese-manganese bond distance observed in [Mn3(BTC)2(DMSO)4]n is 3.602 Å. 2019 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.10.2.180-188.1882 Flores et al. / European Journal of Chemistry 10 (2) (2019) 180-188 183 (a) (b) (c) (d) Figure 1. (a) Fragment of the crystal structure, emphasizing the asymmetric unit. The ellipsoids are represented with 30% of probability and hydrogen atoms were omitted for clarity. (b) Coordination polyhedral Mn1O6 and Mn2O6, representing the geometries of Mn1 and Mn2 metal centers (c) Hourglass trinuclear SBU, based on Mn(II) and (d) 3D expansion of the coordination network, representing DMSO ligands as spacefill and occupying the interior of vacancies. The SBU is highlighted by the dashed circle and Mn(II) metal centers are designed as polyhedral form. Symmetry code: (i) x-1, y, z; (ii) x+1, y, z; (iii) -x_1, y-1/2, - z+3/2; (iv) -x+1, y+1/2, -z+3/2; (v) -x+1, -y+1, -z+2, (vi) x, -y+3/2, z+1/2. 3.2. Topological analysis The simplification used the cluster representation to consider the extension points on the SBU found. The connection of the extension points led to the octahedral and the triangular geometric solids (Figure 2a). 0-, 1- and 2- connected atoms do not contribute to the extension of the network and were omitted. Even if DMSO ligands participate in the coordination environment, they do not contribute to the topology of the net. Thus, the connection of the octahedral and triangular polyhedrons led to the simplified 3D network (Figure 2b); which is classified as a binodal 3,6-connected network, as shown in Figure 2c. The point symbol of this net is (4.62)2 (42 .610.83) and this topology type is reported in the topos&RCSR as rutile RTL framework, indicating that a default high symmetry net was obtained by the combination of octahedral and triangles [38]. We considered that the faces of the tiles display a set of channels that connect cavities. In the case of the manganese-coordination network, the face symbol for the tile is [4.62]+[62.82], which means that 2 faces are 6- rings and that 1 face is a 4-rings, in the light blue tile (Figure 2d). The red tile is formed by 2 faces that are 6-rings and 2 faces that are 8-rings. This result is in accordance with the minimal transitivity principle [39], which states that the number of independent vertices and edges of the net must be as reduced as possible. The crystal structure determination was fundamental to describe these net characteristics. 3.3. Spectroscopic analysis The approximate wavenumbers of the absorptions and their attributions are presented in Figures 3, 4 and Table 3 [40-42]. As observed, the presence of DMSO in the structure was suggested by the appearance of a pair of bands at 2361 and 1331 cm-1, which are assigned, respectively, to the asymmetric and symmetric stretching mode of CH bond from the methyl group of DMSO. A band observed at 1001 cm-1 (IR) and 1007 cm-1 (R) was attributed to ѵ(SO) stretching of O- coordinated DMSO and the band located at 674 (IR) and 677 cm-1 (R) was attributed to ѵ(CS) symmetric stretching mode. IR and R spectra analysis of manganese-coordination network indicate the absence of the bands near 1721 cm-1, characteristic of ѵ(COOH) stretching in the non-ionized carboxyl groups from BTC ligand, endorsing the non- protonated BTC3- form in the structure. The asymmetric ѵ(COO-)as and symmetric ѵ(COO-)s stretchings were observed in the IR as a pair of bands at 1623 and 1548 cm-1 and 1441 and 1378 cm-1, respectively. Therefore two ∆ѵ = [ѵ(COO-)as - ѵ(COO-)s] [43] values referring to the coordination modes of carboxylate groups were determined. The value of the first, ∆ѵ = 182 cm-1 is close to the value found for the ionic form of BTC ligand (∆ѵ = 183 cm-1) and suggests the bridging bidentate coordination mode. The other ∆ѵ = 170 cm-1, may indicate the chelated bidentate coordination mode. 2019 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.10.2.180-188.1882 https://www.ncbi.nlm.nih.gov/books/NBK253956/ https://www.ncbi.nlm.nih.gov/books/NBK253956/ 184 Flores et al. / European Journal of Chemistry 10 (2) (2019) 180-188 (a) (b) (c) (d) Figure 2. (a) The components of the 3D-coordination network, considering the Mn3(-CO2)6 SBU as an octahedron and the tritopic BTC ligands as a triangle. (b) The combination of octahedral and triangles to assembly the RTL rutile-network. (c) Disposition of the nodes (SBU) and the ligands on the P21/c unit cell. (d) Natural tiling for the crystal structure of [Mn3(BTC)2(DMSO)4], displaying the two kinds of tiles (light blue and red) and exhibiting the skeleton (vertices and edges). Figure 3. IR (upper) and R (bottom) spectra of the coordination compound. For R data collection, it was used 4 cm−1 of spectral resolution and 500 scans with a laser power of 10 mW. 2019 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.10.2.180-188.1882 Flores et al. / European Journal of Chemistry 10 (2) (2019) 180-188 185 Table 3. Selected vibrational wavenumbers (cm−1) used as an attempt to assign the most important regions in the experimental spectra of compound *. Vibrational Assignments H3BTC Na3BTC [Mn3(BTC)2(DMSO)4]n ν(CH)as-DMSO 2361 ν(CH)s-DMSO 2331 ν(SO) 1001 / 1007* ν(CS)s 674 / 677* ν(MnO)µ-DMSO 414 / 415* δ(CO)µ-DMSO 577 ν(COO)as 1620 1623 / 1612*, 1548 / 1550* ν(COO)s 1437 1441 / 1454*, 1378 / 1377* ν(COOH) 1721 ∆ѵ 183 182, 170 ν(CC)ar 1605 1573 1587 / 1602* ν(MnO) 541 β(Mn-O-Mn) 386*, 341* * Raman bands are emphasized as *; as = asymmetric, s = symmetric, ar = aromatic, ѵ = stretching, β = bending, δ = rocking. Figure 4. IR spectra of the protonated form of BTC ligand, a sodium salt of BTC ligand and [Mn3(BTC)2(DMSO)4]n. The O-coordination related to the ѵ(MnO) stretching mode was assigned to the two bands observed at 309 and 341 cm-1 in the Raman spectrum. 3.4. PXRD and thermal (TG/DTA) analysis The comparative analysis between PXRD patterns from the sample and the simulated pattern (obtained from SCXRD data), showed the similarities and a good correspondence of the crystalline phases (Figure 5). It is important to emphasize the crystalline phase purity of the sample. The thermal curves TG, DTG and DTA of [Mn3(BTC)2 (DMSO)4]n are displayed in Figure 6. The DTG curve was used as an auxiliary for analysis of the TG data, which suggests that the compound is stable up to 250 °C. The two first and well- defined weight losses, were observed from 250 to 375.4 °C (obs. 17.1 %, calc. 17.5 %) and from 375.4 to 460.8 °C (obs. 17.7 %, calc. 17.5 %) and are attributed to the loss of 2 mol of DMSO. They are endothermic events, observed in the DTA curve. The distinct temperatures to remove the 2 mol of DMSO may suggest that the µ2-O bridging ligand is binding to the metal center more weakly. In the temperature range from 460.8 to 569.2 °C, two intense exothermic events were observed and attributed to thermodecomposition of BTC ligand, involving CO2 (3 mol), C6H3 (1 mol) and 1 mol of C9H3 (obs. 35.2 %, calc. 34.3 %). The final residue was consistent with 3 mol of manganese dioxide per mol of [Mn3(BTC)2 (DMSO)4]n (obs. 30.4 %, calc. 29.3 %). 3.5. Time of flight mass spectrometry (TOF-LDI) The preliminary analysis by time of flight mass spectrometry (TOF-MS) was carried out involving the laser desorption/ionization (LDI). This analysis is based on the mechanism of laser irradiation over a sample incorporated into a matrix capable of absorbing energy in the ultraviolet region. This technique is largely employed in the analysis of large molecules [44] however, analysis of small molecules has been limited by the interference of the matrix signal [45,46]. Thus, new platforms which do not depend on the matrix have been developed, aiming to eliminate the interferences that may be produced. These novel platforms should be capable of producing a minimal background signal, generally at less than 500 Da, allowing the application in the MALDI (Mass spectrometry matrix-assisted laser desorption/ionization) to identify small molecules [47]. The mass spectrum obtained (Figure 7) suggests that [Mn3(BTC)2(DMSO)4]n is fragmented in different ions with mass/charge (m/z) ratio, the most abundant being 285. The LDI-TOF experiment used a pulsed laser of N2 (λ = 337 nm), showing that the compound absorbs the laser energy in at wavelength and produces desorption/ionization without the necessity of a matrix. Consequently, this result may suggest some potential to the application of this material as a matrix in the MALDI technique in the analysis of small molecules, for example, small molecular weight pollutants [48]. 2019 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.10.2.180-188.1882 186 Flores et al. / European Journal of Chemistry 10 (2) (2019) 180-188 Figure 5. Diffractogram obtained from PXRD analysis of [Mn3(BTC)2(DMSO)4]n (experimental) and diffractogram simulated from the data of SCXRD analysis of coordination network. Figure 6. TG (blue), DTG (yellow) and DTA (red) curves obtained for the compound. Figure 7. The spectrum obtained in the TOF-LDI analysis from a pure sample of [Mn3(BTC)2(DMSO)4]n. 2019 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.10.2.180-188.1882 Flores et al. / European Journal of Chemistry 10 (2) (2019) 180-188 187 4. Conclusion Wanting to obtain a metal-organic framework with mixed ligands (acid-acid), through BTC and GLU, a novel tridimen- sional coordination network, based on Mn(II), BTC and DMSO ligand (µ2-O bridging) was obtained. Single crystal X-ray diffraction analysis provided significant insights as to the chemical crystalline structure, enabling topological studies. The reticular synthesis was verified in the context of the molecular building block approach and the junction of triangles and octahedra to assemble a tridimensional coordination network with rutile topology was observed. This RTL network can be classified as binodal, 3,6-connected, and exhibit a (4.62)2(42.610.83) point symbol with transitivity [22,32], obeying the minimal transitivity principle. Spectroscopic analysis of the ∆ѵ = [ѵ(COO)as - ѵ(COO)s] parameter suggests that the carboxylate group from BTC ligand was involved in two distinct coordination modes, bridge, and bidentate chelate. The thermal analysis suggested the stability of the material up to 250 °C and PXRD reinforced the purity of the crystalline phase, whereas the single crystal analysed for the crystal structure determination was representative of the entire. The TOF-MS/LDI experiment showed that [Mn3(BTC)2(DMSO)4]n absorbs the laser energy in λ = 337 nm and possesses a relation of desorption/ ionization, independent of the matrix, with the most abundant peak at m/z 285. These results suggest the potential application of the compound as a matrix for the analysis of small molecules. Acknowledgments The authors wish to thank the Brazilian Research Development Agencies: CNPq, CAPES, and FAPEMIG (CEX- APQ-00947-14 and CEX-APQ-01283-14) for financial support. Supporting information CCDC-1902199 contains the supplementary crystallo- graphic data for this paper. These data can be obtained free of charge via https://www.ccdc.cam.ac.uk/structures/, or by e- mailing data_request@ccdc.cam.ac.uk, or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44(0)1223-336033. Disclosure statement Conflict of interests: The authors declare that they have no conflict of interest. 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Infrared and Raman Spectra of Inorganic and 2019 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.10.2.180-188.1882 https://www.ccdc.cam.ac.uk/structures/ mailto:data_request@ccdc.cam.ac.uk http://orcid.org/0000-%200002-1092-8182 http://orcid.org/0000-0002-5801-7919 http://orcid.org/0000-0003-4499-8549 http://orcid.org/0000-0002-8637-6388 http://orcid.org/0000-0001-9042-9094 http://orcid.org/0000-0002-7113-8870 188 Flores et al. / European Journal of Chemistry 10 (2) (2019) 180-188 Coordination Compounds: Part A, 6th edition, John Wiley & Sons, 2009. [43]. Nakamoto, K. Infrared and Raman Spectra of Inorganic and Coordination Compounds: Part B, 6th edition, John Wiley & Sons, 2009. [44]. Carbonnelle, E.; Mesquita, C.; Bille, E.; Day, N.; Dauphin, B.; Beretti, J. L.; Ferroni, A.; Gutmann, L.; Nassif, X. J. Clin. Biochem. 2011, 44, 104- 109. [45]. Guo, Z.; He, L. Anal. Bioanal. Chem. 2007, 387, 1939-1944. [46]. Guo, Z.; Zhang, Q.; Zou, H.; Guo, B.; Ni, J. Anal. Chem. 2002, 74, 1637- 1641. [47]. Cohen, L. H.; Gusev, A. I. Anal. Bioanal. Chem. 2002, 373, 571-586. [48]. Wang, S.; Niu, H.; Zeng, T.; Zhang, X.; Cao, D.; Cai, Y. Microporous Mesoporous Mater. 2017, 239, 390-395. Copyright © 2019 by Authors. This work is published and licensed by Atlanta Publishing House LLC, Atlanta, GA, USA. The full terms of this license are available at http://www.eurjchem.com/index.php/eurjchem/pages/view/terms and incorporate the Creative Commons Attribution-Non Commercial (CC BY NC) (International, v4.0) License (http://creativecommons.org/licenses/by-nc/4.0). By accessing the work, you hereby accept the Terms. This is an open access article distributed under the terms and conditions of the CC BY NC License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited without any further permission from Atlanta Publishing House LLC (European Journal of Chemistry). No use, distribution or reproduction is permitted which does not comply with these terms. Permissions for commercial use of this work beyond the scope of the License (http://www.eurjchem.com/index.php/eurjchem/pages/view/terms) are administered by Atlanta Publishing House LLC (European Journal of Chemistry). 2019 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.10.2.180-188.1882 http://www.eurjchem.com/index.php/eurjchem/pages/view/terms http://creativecommons.org/licenses/by-nc/4.0 http://www.eurjchem.com/index.php/eurjchem/pages/view/terms 1. Introduction 2. Experimental 2.1. Instrumentation 3. Results and discussion 3.1. Crystal structure description 3.2. Topological analysis 3.3. Spectroscopic analysis 3.4. PXRD and thermal (TG/DTA) analysis 3.5. Time of flight mass spectrometry (TOF-LDI) 4. Conclusion Acknowledgments Supporting information Disclosure statement ORCID References PrintField10: PrintField11: PrintField12: PrintField13: PrintField14: PrintField15: PrintField16: PrintField17: PrintField18: PrintField20: PrintField21: PrintField22: PrintField23: PrintField24: PrintField25: PrintField26: PrintField27: PrintField28: