Unexpected structural complexity of d-block metallosupramolecular architectures within the benzimidazole-phenoxo ligand scaffold for crystal engineering aspects

Design of metallosupramolecular materials encompassing more than one kind of supramolecular interaction can become deceptive, but it is necessary to better understand the concept of the controlled formation of supramolecular systems. Herein, we show the structural diversity of the bis-compartmental phenoxo-benzimidazole ligand H3L1 upon self-assembly with variety of d-block metal ions, accounting for factors such as: counterions, pH, solvent and reaction conditions. Solid-state and solution studies show that the parent ligand can accommodate different forms, related to (de)protonation and proton-transfer, resulting in the formation of mono-, bi- or tetrametallic architectures, which was also confirmed with control studies on the new mono-compartmental phenoxo-benzimidazole H2L2 ligand analogue. For the chosen architectures, structural variables such as porous character, magnetic behaviour or luminescence studies were studied to demonstrate how the form of H3L1 ligand affects the final form of the supramolecular architecture and observed properties. Such complex structural variations within the benzimidazole-phenoxo-type ligand have been demonstrated for the first time and this proof-of-concept can be used to integrate these principles in more sophisticated architectures in the future, combining both the benzimidazole and phenoxide subunits. Ultimately, those principles could be utilized for targeted manipulation of properties through molecular tectonics and crystal engineering aspects.


H NMR solution studies S21
Comparison of H3L 1 and H2L 2 ligands with their semi-closed 1:2 complexes with Co III ions in the presence of perchlorate.Please note that solvent for ligands is d 6 -DMSO, whereas for complexes it is CD3CN.
Comparison of H3L 1 ligand with semi-closed 1:2 complexes with Co III ions in the presence of perchlorate and chloride anions.Please note that solvent for ligand is d 6

I. Materials and methods
The metal salts, organic compounds and solvents were supplied by Merck Chemical Company and POCH.All chemicals mentioned above were of analytical grade quality and were used as obtained without further purification.Fourier Transform Infrared (FT-IR) spectra were performed by means of a FT-IR Bruker IFS 66v/S spectrophotometer, in the range between 400 and 4000 cm -1 with a resolution of 4 cm -1 .An average of 24 scans has been carried out for each sample.The samples were prepared on a KBr pellet under a pressure of 0.01 torr.Mass spectra (ESI-MS) were determined by a Waters Micromass ZQ spectrometer in acetonitrile or methanolic solutions with concentrations ∼10 −4 M. The samples were run in the positiveion mode.Sample solutions were introduced into the mass spectrometer source with a syringe pump with a flow rate of 40 μL min -1 with a capillary voltage of +3 kV and a desolvation temperature of 300 o C. Source temperature was 120 o C. Cone voltage(Vc) was set to 30 V to allow transmission of ions without fragmentation processes.Scanning was performed from m/z = 100 to 2000 for 6 s, and 10 scans were summed to obtain the final spectrum.Simulations of mass spectra were conducted with enviPat programme 2 .Microanalyses were performed using a Elementar Analyser Vario EL III.NMR spectra were run on a Spektrometer NMR Varian VNMR-S 400 MHz spectrometer and were calibrated against the residual protonated solvent signals (DMSO-d6, d 2.50) which are given in parts per million.All electronic absorption spectra were recorded with a Shimadzu UVPC 2001 spectrophotometer, between 220 and 800 nm, in 10 x 10 mm quartz cells using solutions 2 x 10 -5 M with respect to the metal ions.Excitation and emission spectra were measured at room temperature on a Hitachi 7000 spectrofluorimeter with excitation and emission slits of 2.5 nm.Magnetic properties were measured using QD MPMS 2 XL magnetometer.The samples were sealed in plastic foil before the measurements.The 8 was measured in the residue of mother liquor due to its instability in air.The original emu signals were carefully corrected in respect to all diamagnetic contributions (foil and molecular diamagnetism).All fitting and simulations were performed using the procedures included in PHI software. 3
Ligand H3L 1 was prepared as reported previously. 1 After synthesis 1 H NMR was performed to confirm structure and purity of final product.To increase yield of compound 11 the reaction should be carried out in 1:2 ratio (metal : ligand).Compounds (8 -red) and (10 -brown) were obtained from reaction (8) by recrystallization of crude product via slow diffusion methods in MeOH, MeCN/iPr2O system, mixture of brown and red crystals were separated manually.To increase yield of compound 8 the reaction should be carried out in 2:1 ratio (metal : ligand).
Complexes (9, 12 -13) were prepared in the same molar ratio of the ligand to the appropriate metal salt 2:1.To a solution of ligand H2L 2 (64.5 mg, 0.20 mmol) the appropriate metal salt was added (0.10 mmol) (Co(ClO4)2 • 6H2O -9, Zn(CF3SO3)2 -12, Cd(ClO4)2 • 6H2O -13) in 15 ml of MeOH.For complexes (11 -12) yellow solution formed instantly and then triethylamine (0.20 mmol) was added.The color of the solutions has changed to a more intense one and the reaction mixtures were stirred for 24 h at room temperature.For complex (9) brown solution formed instantly with visible brown precipitate.
To the reaction mixture 1 ml of 30% H2O2 was added and reaction was stirred for 24 h at room temperature, which resulted in formation of clear solution.After evaporation of solvent under reduced pressure, the residues were dissolved in minimum volume of MeOH and precipitated by excess of Et2O.Brown (9) and yellow (12 -13), solids were filtered via suction filtration and dried in the vacuum.
Complex Yield: 99.4 mg, 81% based on ligand.Crystal suitable for X-ray analysis were obtained via slow diffusion methods in MeOH, MeCN/PhMe system.IR (KBr, cm  III.Crystallographic data X-ray crystallography Diffraction data were collected by the ω-scan technique, for 2, 3, 7, 9 at 100(1) K, for 8 and 10 at 130(1) K, and for 4 and 6 at room temperature, on Agilent Technologies Xcalibur four-circle diffractometer with Eos CCD detector and graphite-monochromated MoKα radiation (λ=0.71069Å), and for 1, 5 and 11 at 130(1) K and for H3L 1 at room temperature on Agilent Technologies SuperNova four-circle diffractometer with Atlas CCD detector and mirrormonochromated CuKα radiation (λ=1.54178Å).The data were corrected for Lorentz-polarization as well as for absorption effects. 4Precise unit-cell parameters were determined by a least-squares fit of reflections of the highest intensity, chosen from the whole experiment.The structures were solved with SIR92 5 and refined with the full-matrix least-squares procedure on F 2 by SHELXL-2013. 6All non-hydrogen atoms were refined anisotropically, hydrogen atoms were placed in idealized positions and refined as 'riding model' with isotropic displacement parameters set at 1.2 (1.5 for methyl or hydroxyl groups) times Ueq of appropriate carrier atoms.Positions of those hydrogen which cannot be reasonably placed by this procedure (water molecules, some hydroxyl groups) were calculated according to potential hydrogen bonds.The crystals of H3L 1 and 1 turned out to be twinned, (which was taken into account during both data reduction and refinement); the BASF factor, describing the content of one of the component 6 refined at 79.0(3)% for H3L 1 and at 78.0(7)% for 1.
In almost all structures the solvent molecules were found.Additionally, in some of them (2, 5, 7, 8, 10, 11) the large voids filled with diffused electron density were found; as the modellings of solvent molecules were in these cases unsuccessful, the SQUEEZE procedure 7 was applied.

Figure S11
. Absorption spectra of compound 5 in different solvents.P-measurement after 5 days of dissolution.All absorption spectra were recorded using solutions 2 x 10 -5 M with respect to the metal ions.Extinction coefficients are presented in Table S3.

Figure S12
. Absorption spectra of compound 12 in methanol and acetonitrile.All absorption spectra were recorded using solutions 2 x 10 -5 M with respect to the metal ions.Extinction coefficients are presented in Table S3.

Figure S1 .
Figure S1.(top left) Anisotropic ellipsoid representation of the molecule A of a cation (H5L 1 ) 2+ ; ellipsoids are drawn at the 50% probability level, hydrogen atoms are shown as spheres of arbitrary radii, hydrogen bond is shown as thin blue line.(top right) Comparison of two symmetry-independent cations (fitting of the central rings).1

Figure S2 .
Figure S2.A crystal structure of [H5L 1 ](ClO4)2 as seen along b-direction.Anions and solvent molecules are shown in van der Waals spheres representation in order to visualize their filling-structure role.

Figure S3 .
Figure S3.Comparison of H3L 1 and H2L 2 ligands with their semi-closed 1:2 complexes with Co III ions in the presence of perchlorate.Please note that solvent for ligands is d 6 -DMSO, whereas for complexes it is CD3CN.

Figure S4 .
Figure S4.Comparison of H3L1 ligand with semi-closed 1:2 and 1:1 complexes with Co III ions in the presence of perchlorate and chloride anions.Please note that solvent for ligand is d 6 -DMSO, whereas for complexes it is CD3CN.

Figure S7 .
Figure S7.Time-and temperature dependent changes of the [Cd2(H2L 1-O )2](ClO4)2 (1) complex in CD3CN solvent; F-Cstructure is obtained only upon immediate dissolution of crystals of 1 and measurement; t 0 is the moment when strong signal of imine is observed, followed other changes in the spectrum marked with blue marks, t 1 denotes heating to 80 o C, which 'resets' the equilibrium present in solution.

Figure S10 .
Figure S10.Absorption spectra of compound 13.All absorption spectra were recorded using solutions 2 x 10 -5 M with respect to the metal ions.Extinction coefficients are presented in TableS3.

Figure S16 .Figure S17 .
Figure S16.Emission spectra of compound 12 in: a) methanol, b) acetonitrile, c) dimethylformamide, d) dimethylsulfoxide.P-measurement after 5 days of dissolution; wavelength values denote the excitation wavelengths.TableS4.Collected results of quantum yields for complexes 1 and 5 with schematic representation.

Figure S18 .
Figure S18.Absorption spectra of titration of ligand H3L 1 (up) with acid -HCl and (bottom) with basetriethylamine (c = 2 • 10 -5 M in methanol).Spectra show two bands, whose absorption maxima are at λ = 328 nm and λ = 378 nm.During titration with acid, the absorption intensity decreases and a slight hypochromic shift (blueshift) is present.As the first acid equivalent is added, a proportional decrease in absorbance were observed.This indicates the formation of another protonated form of the ligand, respectively H3L 1 → [H4L 1 ] + after the addition of 1 equivalent, and [H4L 1 ] + → [H5L 1 ] 2+ after addition of second equivalent of acid, no further changes were observed at UV spectra, which means that we were able to protonate the ligand to form [H5L 1 ] 2+ (with two additional protons on N atom from imidazole ringcompare with X-ray in Section 2.1.1.).The base titration of the protonated form of the ligand [H5L 1 ] 2+ illustrates its deprotonation with the addition of subsequent base equivalents and the transition, respectively, from the form of [H5L 1 ] 2+ → [H4L 1 ] + → H3L 1 .Further addition of triethylamine did not cause any change in the in absorbance intensity, indicating that triethylamine is too weak a base to yield more deprotonated forms of the ligand ([H 2L 1 ] -, [HL 1 ] 2-, [L 1 ] 3-).