Construction and Photoluminescent Properties of Schiff-Base

2 days ago - The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.9b00454. Tables of ...
0 downloads 0 Views 3MB Size
Download PDF
Article Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX

pubs.acs.org/IC

Construction and Photoluminescent Properties of Schiff-Base Macrocyclic Mono-/Di-/Trinuclear ZnII Complexes with the Common 2‑Ethylthiophene Pendant Arm Fei-Fan Chang,† Wen-Qi Li,‡ Fan-Da Feng,† and Wei Huang*,† †

State Key Laboratory of Coordination Chemistry, Nanjing National Laboratory of Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, Jiangsu Province, 210093, P. R. China ‡ State Key Laboratory of Pharmaceutical Biotechnology, School of Life Science, Nanjing University, Nanjing 210093, P. R. China

Downloaded by UNIV AUTONOMA DE COAHUILA at 06:16:41:808 on June 05, 2019 from https://pubs.acs.org/doi/10.1021/acs.inorgchem.9b00454.

S Supporting Information *

ABSTRACT: A new flexible 2-ethylthiophene pendant-armed dialdehyde (H2tdd) was reacted with 1,3-propanediamine, [(S,S),(R,R),(±)]-1,2-diaminocyclohexane, and 1,2-bis(2-aminoethoxy)ethane, giving birth to 36-membered [2 + 2] Schiff-base macrocyclic trinuclear ZnII complex 1, 18-membered [1 + 1] mononuclear ZnII macrocycles 2−4, chiral/racemic 34-membered [2 + 2] dinuclear ZnII complexes 5−9, and 46-membered [2 + 2] dinuclear ZnII macrocycles 10−12 via ZnII ion template-assisted Schiff-base condensation. It is worth mentioning that the secondary template effects for nitrate and halide counterions have been observed in the 1,3-propanediamine involved imine condensation. In all [2 + 2] ZnII macrocycles, dinuclear complexes 5−9 display a full-folded molecular conformation, while trinuclear complex 1 and dinuclear complexes 10−12 exhibit distinct half-folded structures in the presence or absence of intramolecular π−π stacking interactions between two phenolic rings of the dialdehyde component. Interestingly, a solvent-induced single-crystal-to-single-crystal transformation was first achieved for two types of solvated mononuclear macrocycles 3a and 3b (H2O vs CH3CN) with folded and unfolded ligand conformations. In addition, the photoluminescent properties were studied for this family of Schiff-base macrocyclic ZnII complexes as well as the dialdehyde precursor H2tdd.

■

INTRODUCTION

architectures could be obtained with the combination of flexible dialdehydes and/or diamines.7 As we know, the introduction of heteroatoms into the skeleton of macrocyclic ligands could impact the coordinating sites, cavity size, and even flexibility of the macrocyclic ligands, therefore resulting in a high diversity of structures and functionalities.8 The successful implantation of sulfur atoms into Schiff-base macrocycles has been achieved by preparing certain thiophenolate-containing dialdehydes9 or thiophene2,5-dicarboxaldehydes10 or using a commercially available Scontaining 2,2′-thiobisethylamine instead.11 In one of our previous reports, the sulfur atom was first embedded into the skeleton of a sulfur-extended dialdehyde to produce an in situ air-oxidized sulfone-functionalized Schiff-base macrocyclic complex with dual bioactive sites.12 On the other hand, attempting to introduce a sulfur-containing unit into the pendant arm of extended dialdehyde is believed as another method to build up S-functionalized Schiff-base macrocycles. By following this strategy, thiophene-2-ethylamine was selected to react with 5-chloro-3-(chloromethyl)-2-hydroxy-

Schiff-base macrocycles constitute a versatile and important class of complexes having wide applications in guest-selective binding,1 sensing,2 catalyzing,3 biological system mimicking,4 etc. Generally, there are two approaches to prepare Schiff-base macrocyclic complexes, i.e., metal-free and metal-ion template methods, and the latter one has been proved to be more effective in forming diverse Schiff-base macrocycles, especially for those having flexible dialdehyde and/or diamine moieties to minimize possible isomerization.5 Zn II with the d10 electronic configuration is regarded as a suitable template ion and has been widely used in building up Schiff-base macrocyclic metal complexes because it has a flexible coordination environment with the coordination number varying from 4 to 6, accompanied by the alteration of the coordination configuration (planar square, tetrahedron, trigonal bipyramid, pyramid, octahedron, and triangular prism).6 In comparison with rigid dialdehydes and diamines, the use of flexible ones often leads to severe distortion of the ideal polyhedron for the ZnII coordination centers because of the whole flexibility of resultant macrocyclic ligands, so Schiffbase macrocyclic ZnII complexes bearing more versatile © XXXX American Chemical Society

Received: February 15, 2019

A

DOI: 10.1021/acs.inorgchem.9b00454 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry benzaldehyde to yield a new flexible 2-ethylthiophene pendantarmed dialdehyde (H2tdd in Scheme 1 and Scheme S1) to construct corresponding S-containing Schiff-base macrocycles.

7−12 were studied in the solid state under the same experimental conditions.

■

RESULTS AND DISCUSSION Syntheses and Spectral Characterizations. The new 2ethylthiophene pendant-armed extended dialdehyde (H2tdd) was prepared by a two-step nucleophilic substitution reaction between 5-chloro-3-(chloromethyl)-2-hydroxybenzaldehyde and thiophene-2-ethylamine. Herein, the thiophene unit in thiophene-2-ethylamine leads to increased electronegativity and nucleophilicity for the nitrogen atom in the nucleophilic substitution in comparison with our previously reported 2phenylethanamine.16 As a result, H2tdd was obtained in a higher yield of 80% with a much shorter reaction time of 2 h, and then it was treated with semirigid [(S,S),(R,R),(±)]-1,2diaminocyclohexane, flexible 1,3-propanediamine, and 1,2bis(2-aminoethoxy)ethane with distinct molecular lengths to prepare corresponding 2-ethylthiophene pendant-armed macrocyclic metal complexes through imine condensation reactions in the presence of Zn(NO3)2·6H2O and ZnX2 (X = Cl, Br, I). Because of the use of a flexible pendant-armed dialdehyde and semirigid/flexible diamines as well as the d10 ZnII ion with variable coordination geometries, a family of Schiff-base macrocyclic complexes have been constituted with different macrocyclic sizes ([1 + 1] and [2 + 2]), conformations (unfolded, full-folded, and half-folded), nuclearities (1−3), coordination numbers (4−6), and configurations (tetrahedron, trigonal bipyramid, pyramid, and octahedron) of central metal ions, namely, 36-membered trinuclear complex 1, 18-membered mononuclear complexes 2−4, chiral/racemic 34-membered dinuclear complexes 5−9, and 46-membered dinuclear complexes 10−12 (Scheme 1). It is noticed that the secondary template effects for nitrate and halide counterions have been observed in the 1,3propanediamine involved imine condensation. That is to say, Zn(NO3)2·6H2O and ZnX2 (X = Cl, Br, I) tend to form [2 + 2] trinuclear macrocycle 1 and [1 + 1] mononuclear macrocycles 2−4, respectively. The successful formation of macrocyclic ZnII complexes 1−4 could be assigned and simulated by the electrospray ionization mass spectrometry (ESI-MS) at m/z = 1269.25 for [Zn3O(NO3)(H2La)(H2O)3]+, 502.25 for {[ZnCl2(H2Lb)] − ZnCl2 + H}+ and {[ZnBr2(H2Lb)] − ZnBr2 + H}+, 884.25 for {[ZnBr2(H2Lb)] + 2EtOH + CH3OH + H}+, and 566.17 for {[ZnI2(H2Lb)] − H}+, as shown in Figure 1 and Figures S2−S4. However, the ESI-MS study reveals that the anion effects could not be observed in the cases of chiral/racemic 1,2-diaminocyclohexane and 1,2bis(2-aminoethoxy)ethane, where only [2 + 2] dinuclear macrocyclic ZnII complexes 5−12 could be yielded no matter whether Zn(NO3)2·6H2O or ZnX2 (X = Cl, Br) was used as the template reagent (Figures S5−S12). The above-mentioned anion effects are suggested to originate from the combination of their different coordination capability, steric hindrance, and acidity, which can be regarded as the “secondary template effects” besides the primary cation template.17 It should be mentioned that the secondary template effects are very sensitive to many experimental parameters, such as dialdehyde, diamine, and pH value, and they cannot apply to the structural adjustment of all the Schiff-base macrocyclic complexes. It is noted that a fractional crystallization phenomenon has been observed in the case of [1 + 1] Schiff-base macrocycle 3. Namely, the orange single crystals were first isolated when a considerable amount of water generated from the imine

Scheme 1. Construction of [1 + 1] Mononuclear, [2 + 2] Dinuclear, and Trinuclear Macrocyclic ZnII Complexes

ZnII ion can modulate the ligand luminescence properties by means of chelation enhanced fluorescence (CHEF).13 Therefore, searching for reagents that can efficiently act as fluorescence sensors for ZnII ions has been an active area of research.14 In this context, Schiff-base macrocyclic Zn II complexes are of particular interest because the donation of −CN− nitrogen lone pair electrons to the ZnII centers enhances the fluorescence intensity of Schiff-base macrocycles through the CHEF mechanism, and some pioneering works have been done on photoluminescent properties of rigid Robson-type dinuclear ZnII complexes.15 However, studies on Schiff-base macrocyclic complexes with larger and more flexible multidentate ligands have not been documented yet. Thus, we are motivated to explore this area to investigate the structure−property correlations of our flexible macrocycles, which, in turn, may be useful to develop luminescent materials. As we have mentioned before, the size and structure of final Schiff-base macrocycles are related to the adoption of different kinds of diamine components as well.7 In this work, three kinds of diamines (1,3-propanediamine, [(S,S),(R,R),(±)]-1,2diaminocyclohexane, and 1,2-bis(2-aminoethoxy)ethane) with distinct molecular lengths and flexibility were selected to construct pendant-armed macrocyclic metal complexes through the Schiff-base imine condensation with H2tdd in the presence of a ZnII ion template. As a result, a series of 2ethylthiophene pendant-armed Schiff-base macrocyclic ZnII complexes with different ring sizes, configurations, nuclearities, and coordination modes were yielded by the template-assisted synthesis. In addition, the steady state and time-resolved fluorescence of dialdehyde H2tdd and macrocycles 1−4 and B

DOI: 10.1021/acs.inorgchem.9b00454 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

from the aldehyde groups to Schiff-base CN units as well. With regard to the antimagnetic ZnII complexes with a d10 electronic structure, NMR spectroscopy has been proved to be a feasible technique to verify the formation of Schiff-base macrocyclic ZnII complexes. In this work, 1H NMR spectra have been recorded for pendant-armed dialdehyde H2tdd and corresponding macrocyclic ZnII complexes 1−12, where one can easily distinguish the starting dialdehyde and the formation of the final ZnII macrocyclic products according to the variations of chemical shifts for certain characteristic functional groups in the 1H NMR spectra (Figures S29−S42). For example, after the Schiff-base condensation, the peak at 10.00 ppm for aldehyde protons in extended dialdehyde H2tdd disappears and new peaks assigned as the imine protons are observed in the range of 7.99−8.41 ppm in macrocycles 1−12, indicative of the successful formation of Schiff-base units. It is found that four Schiff-base protons in [2 + 2] dinuclear and trinuclear complexes 1 and 5−12 are divided into two groups, suggesting distinguishable chemical environments for the imine moiety originating from their folded macrocyclic structures, which will be discussed in the following structural analyses. Crystal Structures of Schiff-Base Macrocyclic Complexes 1−5, 7, and 9−11. X-ray single-crystal diffraction analysis of 1 (Figure 2) indicates that it is a 36-membered [2 +

Figure 1. Experimental ESI-MS of ZnII complexes 1 (a) and 3b (b) in CH3OH, together with the calculated isotopic distribution corresponding to the peak at 100% abundance for comparison.

condensation was consumed by forming solvated complex 3a (3·0.5H2O). And then the yellow crystals of another solvated complex 3b (3·CH3CN) began to crystallize from the filtrate, exhibiting a stepwise crystallization process depending on the amount of water in the mother solution. Moreover, the solid state UV−vis absorption spectrum of complex 3b displays an n−π* transition band centered at 382 nm and a weaker ligandto-metal charge transfer (LMCT) peak at 427 nm (Figure S13). With regard to 3a, the solid state UV−vis spectrum reveals an obvious red shift of 45 nm because folded 3a is more delocalized than unfolded 3b owing to the intramolecular π−π stacking interactions between two phenolic rings of the dialdehyde component, which will be further discussed in the following structural analyses. In addition, complex 3b has stronger absorption tails than those of 3a in the lower energy band, which is consistent with their color alteration from orange to yellow. Compared with the absorption band at 341 nm for the ethanol solution of dialdehyde precursor, macrocyclic ZnII complexes 1−12 exhibit different red shifts to 353−370 nm (Figure S14) in the UV−vis spectra, which could be attributed to the formation of azomethine groups with a better delocalized π-system. In addition, the successful construction of an enantiomeric pair of ZnII macrocyclic complexes, i.e., (R,R)-5 and (S,S)-6, was also investigated by circular dichroism (CD) spectra, as can be seen in Figure S15. Complex (R,R)-5 gave two peaks at 381 (−) and 347 (+) nm, while complex (S,S)-6 had two peaks at 377 (+) and 347 (−) nm with the opposite Cotton effects, indicative of the enantiomeric nature of these two chiral macrocyclic complexes. Furthermore, a strong FT-IR absorption peak is observed at 1670 cm−1 in H2tdd, indicative of the presence of aldehyde groups (Figure S16). However, new absorption peaks are found falling within 1638−1618 cm−1 in all macrocyclic ZnII complexes (Figures S17−S28), indicating the transformation

Figure 2. ORTEP diagram (30% thermal probability ellipsoids) of the molecular structure of 1, where all H atoms, uncoordinated anions, and solvent molecules are omitted for clarity (left). Perspective view of the W-like trinuclear ZnII cluster (right).

2] half-folded trinuclear ZnII complex, which looks like a butterfly spreading its wings (left in Figure 2). Three central metal ions are connected by a μ3-oxo atom with the Zn···Zn separations of 3.092(2), 3.110(1), and 3.625(1) Å. It should be pointed out that three ZnII ions adopt a quite distinct coordination configuration. Zn1 and Zn2 are both fivecoordinated by two μ2-phenolic oxygen atoms, two nitrogen atoms of the Schiff-base units, and one μ3-oxo bridge. However, Zn1 is slightly distorted trigonal bipyramidal with a τ value of 0.895,18 while Zn2 is severely distorted pyramidal (τ = 0.330). In contrast, the coordination geometry of Zn3 is distorted six-coordinate octahedral, consisting of two phenolic oxygen atoms (O3, O4), two oxygen atoms (O6, O7) from a nitrate anion, one μ3-oxo atom (O5), and the tertiary nitrogen atom (N4) of one dialdehyde unit. As a result, three ZnII centers with N4O5 donors form a W-like configuration with four subplanes. The mean deviations from the least-squares planes (P1−P4) are 0.043, 0.066, 0.114, and 0.131 Å (right in Figure 2). The dihedral angle between P1 and P3 is 10.3(5)°, and that between P2 and P4 is 5.4(1)°. The formation of this unique W-like trinuclear ZnII cluster with four planar subunits in 1 is believed to be responsible for its strong fluorescence emission. C

DOI: 10.1021/acs.inorgchem.9b00454 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

coordinated with a dramatically twisted pyramidal geometry in 5, 7, 9, and 10 (τ = 0.445, 0.420, 0.432, 0.453) and trigonal bipyramidal geometry in 11 (τ = 0.637, 0.622, and 0.698) (Figure 4). The basal coordination plane for 5, 7, and 9 is

It is worth mentioning that two extended dialdehyde components in the macrocyclic skeleton have different conformations. One looks like a “tuning fork” in which two phenolic rings of the dialdehyde unit adopt a dihedral angle of 23.2(2)°, and the intramolecular π−π stacking interaction is observed between them with the centroid-to-centroid separation of 3.662(1) Å (Figure S43). In contrast, the other dialdehyde moiety is “tripodal” with a large dihedral angle of 65.4(2)°, forming a half-folded conformation for the [2 + 2] macrocyclic ligand. Moreover, the tertiary nitrogen atom is not coordinated in the folded part, which is totally different from the unfolded one. In addition, a strong intramolecular O−H··· O hydrogen bond is observed between the phenolic proton (H1A) and the other phenolic oxygen atom (O2) in the folded dialdehyde unit (Figure S43 and Table S3), whereas no hydrogen bond is found in the unfolded one. With regard to the four 18-membered mononuclear ZnII complexes 2−4, every metal center is out of the macrocyclic plane owing to the size restriction of the [1 + 1] macrocyclic ligand (Figure 3). The coordination geometry of every four-

Figure 4. ORTEP diagrams (30% thermal probability ellipsoids) of the molecular structures of 5, 7, and 9−11, where all H atoms and uncoordinated anions are omitted for clarity.

composed of the N2O2 core, and the apical position of each ZnII center is occupied by a water molecule, an ethanol molecule, and a bromine ion, respectively. The Zn···Zn separations are 4.452(2), 4.424(1), and 5.025(1) Å in 5, 7, and 9, and no μ2-bridging unit is found between the two ZnII centers. In contrast, one oxygen atom from the nitrate ion serves as the μ2 linker connecting two ZnII centers with the Zn···Zn separation of 4.010(1) Å in 10, and one halide ion connects adjacent ZnII ions with the Zn···Zn separation of 3.561(1) and 3.722(1) Å in 11. The structures of complexes 5, 7, and 9 are full-folded, and the conformations of all the dialdehyde units are folded with an identical “tuning fork” structure, in which two phenolic rings from each dialdehyde component in the [2 + 2] macrocyclic ligand are nearly parallel with the dihedral angle of 17.5(2), 17.4(1), and 21.2(1)°. At the same time, intramolecular π−π stacking interactions are found between two adjacent phenolic rings in 5, 7, and 9 with the centroid-to-centroid separations of 3.617(1), 3.661(1), and 3.944(1) Å (Figures S50−S52). However, the conformation for both dialdehyde components in complexes 10 and 11 is found to be unfolded “tripodal”, which is totally different from the “tuning fork + tripodal” in 1 and “double tuning forks” in 5, 7, and 9. Two of four phenolic rings from each dialdehyde unit in the 46membered [2 + 2] macrocyclic ligand are almost parallel with the dihedral angles of 17.0(2)° in 10 and 9.8(2)/25.2(2)° in 11, while the other two rings have much larger dihedral angles of 58.7(2)° in 10 and 88.0(3)/77.8(2)° in 11, displaying another style of half-folded configuration of the whole macrocyclic ligand in the absence of intramolecular π−π stacking interactions. In addition, intramolecular O−H···O hydrogen bonds could be observed between the phenolic protons and phenolic oxygen atoms of adjacent phenolic rings in 7 and 9 (Figures S51 and S52), while O−H···N hydrogen bonds are present between the phenolic protons and the tertiary nitrogen atoms in 10 and 11 (Figures S53 and S54). By analyzing all the obtained structures of Schiff-base macrocyclic ZnII complexes, we come to the conclusion that the selection of our flexible 2-ethylthiophene pendant-armed dialdehyde H2tdd could lead to the construction of a diverse mono-/di-/trinuclear [1 + 1] and [2 + 2] macrocyclic system by means of primary cationic template effects and secondary

Figure 3. ORTEP diagrams (30% thermal probability ellipsoids) of the molecular structures of 2−4, where all H atoms and uncoordinated anions are omitted for clarity.

coordinate tetrahedral ZnII ion is composed of one phenolic oxygen, one nitrogen atom of the imine bond, and two halide ions. Furthermore, only half of the phenolic oxygen atoms and imine units are coordinated with the metal ion in 2−4, while the tertiary nitrogen atom is not. It is interesting to mention that a different ligand conformation is observed for orange crystals 2/3a and yellow crystals 3b/4. The dialdehyde moieties are “tuning fork” in folded 2 and 3a, in which the phenolic rings are almost parallel with the dihedral angles of 13.9(1)/13.2(2)° and 14.1(2)°. Moreover, strong intramolecular (3.480(1)/3.472(1) Å and 3.481(1) Å) and intermolecular (3.605(1)/3.696(1) Å and 3.633(1) Å) π−π stacking interactions could be observed in 2 and 3a, respectively (Figures S44−S47). In contrast, the [1 + 1] macrocyclic ligands in unfolded 3b and 4 are “tripodal” with larger dihedral angles of 52.9(1)° and 61.4(1)°, respectively, and no π−π stacking could be noticed. Additionally, strong intramolecular O−H···O hydrogen bonds could be observed between the phenolic protons (H1A/H4A) and the other phenolic oxygen atoms (O2/O3) in 2 and 3a (Figures S44 and S46), while only O−H···N hydrogen bonds could be noticed in unfolded 3b and 4 (Figures S48 and S49). As for dinuclear ZnII complexes 5, 7, and 9−11 bearing different diamine components, each zinc ion is fiveD

DOI: 10.1021/acs.inorgchem.9b00454 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

which can be verified by both single-crystal and powder X-ray diffraction analyses (Figure 5e). In order to check the reverse SC−SC transformation from yellow crystals 3b to orange crystals 3a, the yellow acetonitrile solvated crystals of 3b were immersed in the mixture solvents of ethanol/water or methanol/water instead of water due to its low solubility in water, but the corresponding SC−SC transformation has not been attained. Many other attempts such as heating and illumination have been tried, too, in which the reverse SC−SC transformation does not work. As for similar Schiff-base macrocyclic complexes 2 and 4, yellow crystals of 2 and orange crystals of 4 can also be collected via stepwise crystallization in addition to the above-mentioned crystal structures of orange and yellow complexes 2 and 4, and parallel experiments for them indicate the same one-way SC− SC transformation. In fact, by analyzing the crystal structures of all our mono-/di-/trinuclear Schiff-base macrocyclic ZnII complexes, it is deduced that this kind of SC−SC transformation could only be observed in mononuclear ZnII complexes 2−4 since the lack of fixation of multiple coordination bonds in the mononuclear NO coordination environment makes possible the conformation alteration between folded and unfolded [1 + 1] macrocyclic ligand. Photoluminescent Properties. Considering many d10 metal compounds exhibit excellent luminescence properties,22 the steady state fluorescence and time-resolved single photon counting (TCSPC) of our Schiff-base macrocyclic ZnII complexes together with the dialdehyde H 2 tdd were investigated to explore the relationship between their structures and photoluminescence properties. The emission (Figure 6) and 3D (Figures S60−S71) fluorescence spectra of

complementary template effects during the processes of reversible imine formation and cleavage (also known as dynamic covalent chemistry).17,19 In this work, the flexible macrocyclic ligands exhibit different kinds of conformations including full-folded, half-folded, and unfolded ones, so as to meet the spatial requirements for forming coordination spheres of central ZnII ions with alterable coordination number and configuration. On the other hand, the use of extended dialdehyde H2tdd allows for the formation of a small-sized [1 + 1] macrocycle with a mononuclear outer-ring coordination style and large-sized twisted [2 + 2] macrocycles with the longer Zn···Zn distances, which are different from classical Robson-type dinuclear macrocycles with the rigid and planar [2 + 2] backbone.20 In other words, the rational combination of flexible macrocyclic ligands and metal ions with variable coordination environments is vital for templateassisted reversible imine chemistry, particularly in constituting charming architectures via the macrocyclic effects. Single-Crystal-to-Single-Crystal Transformation between 3a and 3b. Single-crystal-to-single-crystal (SC−SC) transformation is of significant interest in terms of crystal engineering, chemical sensing as well as material science, and most of such transformations were studied in porous coordination polymers (PCPs) or metal−organic frameworks (MOFs).21 They are usually achieved by a variety of methods, including photochemical reaction, cation exchange, and ligand and solvent exchange, with the retention of the polymeric networks. However, the SC−SC process observed in flexible Schiff-base macrocyclic complexes has not been reported yet. With solvated single crystals of 3a and 3b bearing distinguishing color in hand, a possible SC−SC transformation between them has been carried out. It was discovered that 3a and 3b display one-way solvent-induced SC−SC transformation (Figure 5). As shown in Figure 5b−d, when the orange

Figure 6. Fluorescence emission spectra for dialdehyde H2tdd upon excitation at λex = 390 nm and Schiff-base macrocyclic ZnII complexes 1−12 (λex = 465 nm) in the solid state at room temperature. Figure 5. One-way SC−SC transformation for [1 + 1] mononuclear macrocyclic ZnII complexes (from orange 3a to yellow 3b).

steady state fluorescence for H2tdd and macrocycles 1−12 were carried out for full comparison, where their excitation and emission wavelengths are summarized in Table 1. Upon excitation at 395 nm, dialdehyde precursor H2tdd exhibits a fluorescence emission band centered at 522 nm with a large Stokes shift of 12.244 × 10−20 J. In contrast, the emission spectra of macrocycles 1, 3b, 4, and 10−12 have peaks with maxima at 520 and 507−514 nm showing a slight blue shift, and 5−9 display red-shifted bands in the range of 531−539 nm, accompanied by the remarkable decrease of their Stokes shifts of 3.186 × 10−20−5.869 × 10−20 J. However, folded [1 + 1] mononuclear macrocycles 2 and 3a exhibit significant redshifted emissions centered at 585 and 583 nm upon excitation

semihydrate single crystals of 3a were immersed into acetonitrile at room temperature, they gradually transformed to yellow acetonitrile solvated crystals of 3b accompanied by the conformation alteration for the macrocyclic ligand from folded in 3a to unfolded in 3b (Figure 5a). The microscopic picture taken after 12 h indicates the partial SC−SC transformation of the single crystals 3a, in which most small crystals have been transformed into yellow crystals 3b and some big ones are still experiencing the SC−SC transformation. After being soaked into acetonitrile for 24 h, all the orange crystals 3a have been completely converted to 3b, E

DOI: 10.1021/acs.inorgchem.9b00454 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

Table 1. Excitation (λex) and Emission (λem) Wavelengths, Stokes Shifts (Δλ), Fluorescence Quantum Yields (Φ), Lifetimes (τ), and Radiative (kr) and Nonradiative Rate Constants (knr) for H2tdd and Schiff-Base Macrocyclic ZnII Complexes 1−4 and 7−12 in the Solid State compound

λex (nm)

λem (nm)

Δλ (× 10−20 J)

H2tdd 1 2 3a 3b 4 7 8 9 10 11 12

395 480 465 465 465 465 465 465 465 465 465 465

522 520 585 583 512 514 539 531 533 512 507 509

12.244 3.186 8.769 8.652 3.924 4.075 5.869 5.313 5.454 3.924 3.541 3.695

Φ (%)

τ (ns)

kr (× 106 s−1)

knr (× 108 s−1)

± ± ± ± ± ± ± ± ± ± ± ±

6.70(1) 0.75(1) 1.30(1) 1.33(1) 1.77(1) 2.81(2) 1.41(2) 1.40(1) 1.91(2) 0.93(2) 0.89(1) 0.74(1)

1.42 85.08 9.06 12.36 14.30 24.02 39.63 36.73 26.46 63.66 62.91 71.61

1.48 12.51 7.60 7.39 5.52 3.44 6.66 6.75 4.96 10.04 10.59 12.74

0.95 6.37 1.60 1.91 2.51 3.19 5.62 5.16 5.07 5.96 5.61 5.32

at 465 nm with large Stokes shifts of 8.652 × 10−20 and 8.769 × 10−20 J. Furthermore, the fluorescence quantum yields Φ of H2tdd and macrocycles 1−4 and 7−12 were measured by using the integrating sphere method, and the fluorescence lifetimes were determined from time-resolved intensity decay by the method of time correlated single-photon counting (TCSPC) using a diode laser at 405 nm as the light source (Table 1 and Figures S72−S83). The rate constants of both radiative (kr) and nonradiative (knr) decay processes were calculated using Φ = krτ and τ−1 = kr + knr and are listed in Table 1. It is evidenced from the list that both kr and knr for complexes 1−4 and 7−12 are increased in comparison to dialdehyde H2tdd, and the kr and quantum yields Φ for them follow an approximate relationship: the higher the value of kr, the higher the value of Φ.15b As the relative increase of kr (∼59.9 times for 1, ∼6.4− 8.7 for 2 and 3a, ∼10.1−16.9 times for 3b and 4, ∼18.6−27.9 for 7−9, and ∼44.3−50.4 times for 10−12) is greater than that of knr (∼8.5 times for 1, ∼5.0−5.1 for 2 and 3a, ∼2.3−3.7 times for 3b and 4, ∼3.4−4.6 for 7−9, and ∼6.8−8.6 times for 10−12), the induced fluorescence enhancement can be ascribed to the increase of kr. This remarkable improvement of fluorescence intensities and quantum yields after ZnII ion complexation could be assigned as the coordination effects, and it is considered that the incorporation of ZnII ions has narrowed down the energy gap between π and π* by forming covalent bonds of N−M and O−M, and also the donation of the imine nitrogen lone pair electrons to the ZnII centers strengthens the fluorescence intensity of Schiff-base macrocycles through the CHEF mechanism.23 It is worthwhile to point out that trinuclear ZnII complex 1 has the highest fluorescence quantum yield Φ and radiative rate constant kr among all the Schiff-base macrocyclic ZnII complexes 1−12, which might be the increased structural rigidity through forming the unique W-like conformation with four planar subunits, thus effectively reducing the loss of energy via vibrational motions, increasing the value of the radiative rate constant and enhancing the fluorescence intensity. Meanwhile, the high rigidity of the molecular structure of 1 could be evidenced by the smallest Stokes shift of 40 nm. In addition, the coordination environment of three ZnII centers in 1 has the smallest τ deviations from the ideal trigonal bipyramidal and pyramidal in all our macrocyclic complexes. The energy-preferential coordination environment for ZnII centers indicates the minimum steric hindrance and

0.03 0.03 0.01 0.10 0.05 0.13 0.03 0.09 0.06 0.12 0.05 0.11

ring tension, which is also responsible for the observed highest fluorescence quantum yield and smallest Stokes shift. The values of Φ and kr for [1 + 1] mononuclear ZnII macrocycles 2−4 are significantly lower than those of dinuclear and trinuclear ZnII complexes which may be ascribed to their coordination environments. Namely, the metal center in 2−4 is out of the macrocyclic plane and only coordinated with half of the phenolic oxygen atoms and imine units. This NO coordination configuration results in lower structural rigidity and weaker CHEF effects, therefore increasing the loss of the energy through nonradiative transition processes and decreasing the fluorescence quantum yields. Furthermore, folded macrocycles 2 and 3a have lower Φ values and larger Stokes shifts compared with unfolded 3b and 4, which could be supported by the simultaneous internal and external quenching of luminescence through energy-transfer processes via strong alternate intramolecular and intermolecular π−π stacking interactions observed in the former (Figures S45 and S47). As for the [2 + 2] dinuclear ZnII macrocycles 7−9, the formation of a double N2O2 equatorial coordination plane and the coordination configuration (five-coordinated with twisted pyramidal geometry) for each ZnII center are similar to that of typical Robson-type Schiff-base macrocycles, which guarantee the rigidity and planarity of fluorescence-active subunits. And also, the fluorescence quantum yields of our complexes (5.07− 5.62%) are comparable to those reported in the literature.15 It is worth mentioning that the quantum yields of half-folded [2 + 2] dinuclear μ2-bridged macrocycles 10−12 are larger than those of full-folded 7−9 even with the adoption of a nonplanar N2O2 coordination mode as well as more flexible 1,2-bis(2aminoethoxy)ethane components in 10−12. This can be originated from the fixation of the μ2-bridge linking two ZnII centers which has decreased the vibrational motions of the molecular structure. On the other hand, the absence of intramolecular π−π stacking in half-folded macrocycles 10−12 also contributes to the enhancement of fluorescence intensity in contrast to full-folded macrocycles 7−9 having intramolecular π−π stacking. Additionally, the fluorescence quantum yields of [2 + 2] dinuclear macrocycles 7−12 follow the order of 7 > 8 > 9 and 10 > 11 > 12 due to the coordinated halide effects (I > Br > CI) which would increase the external (but intramolecular) perturbation of the spin− orbital coupling in the π-electron orbitals, resulting in the halide-to-ligand charge transfer (XLCT) and decreasing the final fluorescence quantum yield.24 F

DOI: 10.1021/acs.inorgchem.9b00454 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry Table 2. Crystal Data and Structural Refinements for Complexes 1−4 empirical formula formula weight temperature/K wavelength/Å crystal size/mm crystal system space group a/Å b/Å c/Å α/deg β/deg γ/deg V/Å3 Z/Dcalcd (g/cm3) F(000) μ/mm−1 hmin/hmax kmin/kmax lmin/lmax data/parameters R1, wR2 [I > 2σ(I)]a R1, wR2 (all data)a S max/min Δρ/e Å−3

1

2

3a

3b

4

C52H54Cl4N8O12S2Zn3 1385.06 291(2) 0.71073 0.12 × 0.10 × 0.10 triclinic P1̅ 13.036(1) 15.167(2) 16.160(2) 109.995(3) 103.014(4) 95.354(4) 2874.2(6) 2/1.600 1416 1.568 −13/15 −18/18 −19/17 10085/755 R1 = 0.0893 wR2 = 0.2234 R1 = 0.1108 wR2 = 0.2344 1.053 5.835/−2.293

C25H25Cl4N3O2SZn 638.71 150(2) 0.71073 0.12 × 0.10 × 0.10 triclinic P1̅ 13.003(1) 13.482(1) 18.671(1) 105.240(1) 104.104(1) 105.853(2) 2857.0(2) 4/1.485 1304 1.334 −16/16 −17/15 −24/22 13127/651 R1 = 0.0715 wR2 = 0.1955 R1 = 0.0939 wR2 = 0.2070 1.107 4.091/−1.541

C50H52Br4Cl4N6O5S2Zn2 1473.27 296(2) 0.71073 0.12 × 0.10 × 0.10 monoclinic C2/c 21.469(1) 15.930(1) 20.542(3) 90 121.202(1) 90 6008.8(10) 4/1.629 2936 3.753 −25/19 −16/18 −21/24 5288/3810 R1 = 0.0606 wR2 = 0.1824 R1 = 0.0844 wR2 = 0.1954 1.105 1.765/−0.705

C27H28Br2Cl2N4O2SZn 768.68 150(2) 0.71073 0.12 × 0.10 × 0.10 monoclinic P21/n 11.192(1) 20.735(2) 12.816(1) 90 93.040(2) 90 2970.1(4) 4/1.719 1536 3.801 −11/14 −26/24 −16/16 6840/373 R1 = 0.0386 wR2 = 0.0985 R1 = 0.0499 wR2 = 0.1046 1.033 1.418/−0.839

C27H28I2Cl2N4O2SZn 862.66 150(2) 0.71073 0.12 × 0.12 × 0.10 monoclinic P21/n 11.792(1) 20.548(1) 12.755(1) 90 94.179(1) 90 3082.2(2) 4/1.859 1680 3.073 −14/15 −26/16 −16/16 7061/373 R1 = 0.0320 wR2 = 0.0473 R1 = 0.0683 wR2 = 0.0734 1.009 1.376/−0.819

R1 = ∑||Fo| − |Fc||/∑|Fo|, wR2 = [∑[w(Fo2 − Fc2)2]/∑w(Fo2)2]1/2.

a

Table 3. Crystal Data and Structural Refinements for Complexes 5, 7, and 9−11 empirical formula formula weight temperature/K wavelength/Å crystal size/mm crystal system space group a/Å b/Å c/Å α/deg β/deg γ/deg V/Å3 Z/Dcalcd (g/cm3) F(000) μ/mm−1 hmin/hmax kmin/kmax lmin/lmax data/parameters R1, wR2 [I > 2σ(I)]a R1, wR2 (all data)a S max/min Δρ/e Å−3

5

7

9

10

11

C56H60Cl4N8O12S2Zn2 1373.78 291(2) 0.71073 0.12 × 0.10 × 0.10 tetragonal P43212 14.713(1) 14.713(1) 34.545(2) 90 90 90 7478.4(6) 4/1.220 2832 0.895 −17/16 −17/17 −29/41 6583/425 R1 = 0.0548 wR2 = 0.1446 R1 = 0.0666 wR2 = 0.1498 1.006 0.671/−0.533

C60H68Cl4N8O12S2Zn2 1429.88 291(2) 0.71073 0.12 × 0.12 × 0.10 tetragonal P4/ncc 27.590(2) 27.590(2) 18.448(2) 90 90 90 14043(2) 8/1.353 5920 0.956 −32/28 −32/32 −21/21 6195/430 R1 = 0.0626 wR2 = 0.1700 R1 = 0.0815 wR2 = 0.1825 1.064 0.599/−0.624

C56H56Br2Cl4N6O4S2Zn2 1373.54 291(2) 0.71073 0.12 × 0.12 × 0.10 monoclinic C2/c 24.957(5) 15.786(3) 17.046(4) 90 114.736(4) 90 6100(2) 4/1.496 2784 2.388 −29/32 −20/20 −21/22 6992/362 R1 = 0.0481 wR2 = 0.1080 R1 = 0.0973 wR2 = 0.1213 1.000 0.807/−0.737

C56H60Cl4N8O14S2Zn2 1405.78 291(2) 0.71073 0.11 × 0.10 × 0.10 orthorhombic Fdd2 35.025(3) 11.820(1) 33.758(3) 90 90 90 13975(2) 8/1.336 5792 0.961 −45/45 −14/15 −36/43 6847/391 R1 = 0.0581 wR2 = 0.1479 R1 = 0.0704 wR2 = 0.1545 1.048 1.711/−0.821

C168H178Cl15N18O24S6Zn6 3949.60 150(2) 0.71073 0.10 × 0.10 × 0.10 monoclinic C2/c 37.478(3) 22.352(2) 29.186(4) 90 118.363(2) 90 21514(4) 4/1.219 8140 0.961 −44/44 −24/26 −34/34 18941/1068 R1 = 0.0930 wR2 = 0.2447 R1 = 0.1342 wR2 = 0.2248 1.080 1.470/−0.876

R1 = ∑||Fo| − |Fc||/∑|Fo|, wR2 = [∑[w(Fo2 − Fc2)2]/∑w(Fo2)2]1/2.

a

G

DOI: 10.1021/acs.inorgchem.9b00454 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry It is concluded that the fluorescence property of our series of flexible Schiff-base macrocyclic ZnII complexes is affected by several parameters. First of all, it is nuclearity dependent with the fluorescence yields increasing in the order of trinuclear > dinuclear > mononuclear. Second, it is closely related to the coordination fashion and impacted by the deviation degree from the ideal coordination sphere. Third, the size, conformation, and flexibility of macrocyclic ligands play essential roles. Lastly, the supramolecular interactions such as heavy atom effects and intramolecular and/or intermolecular π−π stacking could influence the fluorescence behavior as well.

Tables of crystal data and structural refinements for complex 12 (the quality of crystal data cannot meet the publishing requirements), selected bond distances, angles, and hydrogen-bonding interactions, figures of ESI-MS, UV−vis, circular dichroism, 1H NMR, FT-IR, supramolecular interactions, 3D fluorescence spectra, time-resolved fluorescence decay, and fitting curve for related complexes (PDF) Accession Codes

CCDC 1845748−1845757 and 1896688 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/ cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

■

CONCLUSION In summary, a new extended dialdehyde H2tdd with the 2ethylthiophene pendant arm has been synthesized and reacted with three kinds of diamines to produce corresponding Schiffbase macrocyclic complexes in the presence of a ZnII ion template. As a result, one 36-membered [2 + 2] half-folded Schiff-base macrocyclic trinuclear ZnII complex (1), four 18membered [1 + 1] mononuclear ZnII macrocycles (2−4), five chiral/racemic 34-membered [2 + 2] full-folded dinuclear ZnII complexes (5−9), and three 46-membered [2 + 2] half-folded dinuclear ZnII macrocycles (10−12) were successfully yielded (Tables 2 and 3). With regard to [2 + 2] dinuclear ZnII complexes 5−9 and 10−12, the adoption of semirigid [(S,S),(R,R),(±)]-1,2-diaminocyclohexane and flexible 1,2bis(2-aminoethoxy)ethane leads to the formation of apparently different macrocyclic conformations, indicating the influences of the molecular length and flexibility of diamines on the resultant structures of the imine condensation reactions. It is noted that the secondary template effects for nitrate and halide counterions are found to play important roles in organizing the final macrocyclic complexes in the case of 1,3-propanediamine. In addition, [1 + 1] mononuclear macrocycle 3 displays fractional crystallization and 3a could be completely converted to 3b via a solvent induced SC−SC structural transformation, in which folded and unfolded solvates 3a and 3b exhibit distinguishable color and spectral behavior. Moreover, the luminescent property was investigated for this family of flexible Schiff-base macrocyclic ZnII complexes varying in nuclearity, size, structural conformation, and coordination configuration. The current work is suggested to present the structural diversification of Schiff-base macrocyclic complexes by combining a flexible 2-ethylthiophene based dialdehyde and semirigid/flexible diamines in the presence of a ZnII ion template with alterable coordination number and modes. Compared with the conventional rigid and dinuclear Robsontype macrocyclic complexes, the selection of flexible macrocyclic ligands with more matching possibilities allows for the formation of more preferred states to meet the stereochemical requirements of ZnII ion complexation, and the acquirement of their crystal structures prompts us to study and reveal their structure−property relationships. We anticipate the rational design of flexible pendant-armed dialdehydes and the construction of flexible macrocyclic complexes could open wide perspectives for the investigations on dynamic covalent chemistry and multifunctional materials.

■

■

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Wei Huang: 0000-0002-1071-1055 Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS This work was financially supported by the National Natural Science Foundation of China (No. 21871133) and the National Natural Science Foundation of Jiangsu Province (No. BK20171334).

■

REFERENCES

(1) (a) Akine, S.; Utsuno, F.; Piao, S.; Orita, H.; Tsuzuki, S.; Nabeshima, T. Synthesis, ion recognition ability, and metal-assisted aggregation behavior of dinuclear metallohosts having a bis(saloph) macrocyclic ligand. Inorg. Chem. 2016, 55, 810−821. (b) Janczak, J.; Prochowicz, D.; Lewinski, J.; Fairen-Jimenez, D.; Bereta, T.; Lisowski, J. Trinuclear cage-like Zn(II) macrocyclic complexes: enantiomeric recognition and gas adsorption properties. Chem. - Eur. J. 2016, 22, 598−609. (2) (a) Jiang, X. J.; Li, M.; Lu, H. L.; Xu, L. H.; Xu, H.; Zang, S. Q.; Tang, M. S.; Hou, H. W.; Mak, T. C. A highly sensitive C3-symmetric Schiff-base fluorescent probe for Cd2+. Inorg. Chem. 2014, 53, 12665− 12667. (b) Ullmann, S.; Schnorr, R.; Handke, M.; Laube, C.; Abel, B.; Matysik, J.; Findeisen, M.; Ruger, R.; Heine, T.; Kersting, B. Zn2+-ion sensing by fluorescent Schiff base calix[4]arene macrocycles. Chem. Eur. J. 2017, 23, 3824−3827. (3) (a) Cozzi, P. G. Enantioselective alkynylation of ketones catalyzed by Zn(salen) complexes. Angew. Chem., Int. Ed. 2003, 42, 2895−2898. (b) Cozzi, P. G. Metal-salen Schiff base complexes in catalysis: practical aspects. Chem. Soc. Rev. 2004, 33, 410−421. (c) Gupta, K. C.; Sutar, A. K. Catalytic activities of Schiff base transition metal complexes. Coord. Chem. Rev. 2008, 252, 1420−1450. (d) Matsunaga, S.; Shibasaki, M. Recent advances in cooperative bimetallic asymmetric catalysis: dinuclear Schiff base complexes. Chem. Commun. 2014, 50, 1044−1057. (e) Romain, C.; Bennington, M. S.; White, A. J.; Williams, C. K.; Brooker, S. Macrocyclic dizinc(II) alkyl and alkoxide complexes: reversible CO2 uptake and polymerization catalysis testing. Inorg. Chem. 2015, 54, 11842−11851. (4) (a) Kato, H. E.; Inoue, K.; Abe-Yoshizumi, R.; Kato, Y.; Ono, H.; Konno, M.; Hososhima, S.; Ishizuka, T.; Hoque, M. R.; Kunitomo, H.; Ito, J.; Yoshizawa, S.; Yamashita, K.; Takemoto, M.; Nishizawa, T.; Taniguchi, R.; Kogure, K.; Maturana, A. D.; Iino, Y.; Yawo, H.; Ishitani, R.; Kandori, H.; Nureki, O. Structural basis for Na(+) transport mechanism by a light-driven Na(+) pump. Nature 2015, 521, 48−53. (b) Lian, W. J.; Wang, X. T.; Xie, C. Z.; Tian, H.; Song,

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.9b00454. H

DOI: 10.1021/acs.inorgchem.9b00454 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

structures of a free macrocycle and of a disilver complex. J. Chem. Soc., Dalton Trans. 1984, 2281−2288. (c) Won, D. H.; Lee, C. H. Thiophene-containing Schiff-base macrocycles: intermediate compounds between macroaromatics and azamacrocycles. Tetrahedron Lett. 2001, 42, 1969−1972. (11) (a) Guerriero, P.; Casellato, U.; Tamburini, S.; Vigato, P. A.; Graziani, R. Lanthanide complexes with compartmental schiff-bases. Inorg. Chim. Acta 1987, 129, 127−138. (b) Guerriero, P.; Tarnburini, S.; Vigato, P. A. From mononuclear to polynuclear macrocyclic or macroacyclic complexes. Coord. Chem. Rev. 1995, 139, 17−243. (12) Feng, G. F.; Shi, Y. S.; Zhang, L.; Shi, R. G.; Huang, W.; Wang, R. Y. Air-oxidation from sulfur to sulfone-bridged Schiff-base macrocyclic complexes showing enhanced antimicrobial activities. Sci. Rep. 2017, 7, 15881−15886. (13) Hens, A.; Mondal, P.; Rajak, K. K. Synthesis, structure and spectral properties of O, N, N coordinating ligands and their neutral Zn(II) complexes: a combined experimental and theoretical study. Dalton Trans. 2013, 42, 14905−14915. (b) Lohar, S.; Pal, S.; Mukherjee, M.; Maji, A.; Demitri, N.; Chattopadhyay, P. A turn-on green channel Zn2+ sensor and the resulting zinc(ii) complex as a red channel HPO42− ion sensor: a new approach. RSC Adv. 2017, 7, 25528−25534. (14) (a) Hens, A.; Mondal, P.; Rajak, K. K. Synthesis, structure and spectral properties of O,N,N coordinating ligands and their neutral Zn(II) complexes: a combined experimental and theoretical study. Dalton Trans. 2013, 42, 14905−14915. (b) Pandey, R.; Kumar, P.; Singh, A. K.; Shahid, M.; Li, P. Z.; Singh, S. K.; Xu, Q.; Misra, A.; Pandey, D. S. Fluorescent zinc(II) complex exhibiting “on-off-on” switching toward Cu2+ and Ag+ ions. Inorg. Chem. 2011, 50, 3189− 3197. (15) (a) Dutta, B.; Bag, P.; Florke, U.; Nag, K. Dinuclear zinc(II) complexes of tetraiminodiphenol macrocycles and their interactions with carboxylate anions and amino acids. photoluminescence, equilibria, and structure. Inorg. Chem. 2005, 44, 147−157. (b) Majumder, S.; Mandal, L.; Mohanta, S. Syntheses, structures, and steady state and time resolved photophysical properties of a tetraiminodiphenol macrocyclic ligand and its dinuclear zinc(II)/ cadmium(II) complexes with coordinating and noncoordinating anions. Inorg. Chem. 2012, 51, 8739−8749. (16) Zhang, K.; Jin, C.; Chen, H. Q.; Yin, G.; Huang, W. Construction of pendant-armed Schiff-base macrocyclic dinuclear zinc complexes and their selective recognition of acetate ions. Chem. Asian J. 2014, 9, 2534−2541. (17) Chang, F. F.; Zhang, K.; Huang, W. Schiff-base macrocyclic Zn(II) complexes based upon flexible pendant-armed extended dialdehydes. Dalton Trans. 2019, 48, 363−369. (18) Addison, A. W.; Rao, T. N.; Reedijk, J.; van Rijn, J.; Verschoor, G. C. Synthesis, structure, and spectroscopic properties of copper(II) compounds containing nitrogen−sulphur donor ligands; the crystal and molecular structure of aqua[1,7-bis(N-methylbenzimidazol-2′yl)-2,6-dithiaheptane]copper(II) perchlorate. J. Chem. Soc., Dalton Trans. 1984, 1349−1356. (19) Belowich, M. E.; Stoddart, J. F. Dynamic imine chemistry. Chem. Soc. Rev. 2012, 41, 2003−2024. (20) Huang, W.; Zhu, H. B.; Gou, S. H. Self-assembly directed by dinuclear zinc(II) macrocyclic species. Coord. Chem. Rev. 2006, 250, 414−423. (21) (a) Huang, Z.; White, P. S.; Brookhart, M. Ligand exchanges and selective catalytic hydrogenation in molecular single crystals. Nature 2010, 465, 598−601. (b) Lan, Y. Q.; Jiang, H. L.; Li, S. L.; Xu, Q. Solvent-induced controllable synthesis, single-crystal to singlecrystal transformation and encapsulation of Alq3 for modulated luminescence in (4,8)-connected metal-organic frameworks. Inorg. Chem. 2012, 51, 7484−91. (c) Halder, G. J.; Kepert, C. J. Single crystal to single crystal structural transformations in molecular framework materials. Aust. J. Chem. 2006, 59, 597−604. (22) (a) Pajuelo-Corral, O.; Rodriguez-Dieguez, A.; Garcia, J. A.; San Sebastian, E.; Seco, J. M.; Cepeda, J. Chiral coordination polymers based on d(10) metals and 2-aminonicotinate with blue

X. Q.; Pan, H. T.; Qiao, X.; Xu, J. Y. Mixed-ligand copper(II) Schiff base complexes: the role of the co-ligand in DNA binding, DNA cleavage, protein binding and cytotoxicity. Dalton Trans. 2016, 45, 9073−9087. (5) (a) Borisova, N. E.; Reshetova, M. D.; Ustynyuk, Y. A. Metalfree methods in the synthesis of macrocyclic schiff bases. Chem. Rev. 2007, 107, 46−79. (b) Meyer, C. D.; Joiner, C. S.; Stoddart, J. F. Template-directed synthesis employing reversible imine bond formation. Chem. Soc. Rev. 2007, 36, 1705−1723. (c) Vigato, P. A.; Tamburini, S.; Bertolo, L. The development of compartmental macrocyclic Schiff bases and related polyamine derivatives. Coord. Chem. Rev. 2007, 251, 1311−1492. (d) Chen, Q. Y.; Luo, Q. H.; Hu, X. L.; Shen, M. C.; Chen, J. T. Heterodinuclear cryptates [EuML(dmf)](ClO4)2 (M = Ca, Cd, Ni, Zn): tuning the luminescence of europium(III) through the selection of the second metal ion. Chem. - Eur. J. 2002, 8, 3984−3990. (e) Browne, C.; Ronson, T. K.; Nitschke, J. R. Palladium-templated subcomponent self-assembly of macrocycles, catenanes, and rotaxanes. Angew. Chem., Int. Ed. 2014, 53, 10701−10705. (6) (a) Erxleben, A. Structures and properties of Zn(II) coordination polymers. Coord. Chem. Rev. 2003, 246, 203−228. (b) Frischmann, P. D.; Gallant, A. J.; Chong, J. H.; MacLachlan, M. J. Zinc carboxylate cluster formation in conjugated metallomacrocycles: evidence for templation. Inorg. Chem. 2008, 47, 101−112. (c) Atkins, A. J.; Black, D.; Finn, R. L.; Marin-Becerra, A.; Blake, A. J.; RuizRamirez, L.; Li, W. S.; Schroder, M. Synthesis and structure of mononuclear and binuclear zinc(II) compartmental macrocyclic complexes. Dalton Trans. 2003, 1730−1737. (d) Vigato, P. A.; Peruzzo, V.; Tamburini, S. Acyclic and cyclic compartmental ligands: recent results and perspectives. Coord. Chem. Rev. 2012, 256, 953− 1114. (7) Vigato, P. A.; Tamburini, S. The challenge of cyclic and acyclic Schiff bases and related derivatives. Coord. Chem. Rev. 2004, 248, 1717−2128. (8) (a) Danks, J. P.; Champness, N. R.; Schroder, M. Chemistry of mixed nitrogen- and sulfur-donor tridentate macrocycles. Coord. Chem. Rev. 1998, 174, 417−468. (b) Lindoy, L. F. Heavy metal ion chemistry of linked macrocyclic systems incorporating oxygen and/or sulfur in their donor sets. Coord. Chem. Rev. 1998, 174, 327−342. (c) Kang, E. J.; Lee, S. Y.; Lee, H.; Lee, S. S. Sulfur-containing mixeddonor tribenzo-macrocycles and their endo- and exocyclic supramolecular silver(I) and copper(I) complexes. Inorg. Chem. 2010, 49, 7510−7520. (d) Adam, K. R.; Arshad, S. P. H.; Baldwin, D. S.; Duckworth, P. A.; Leong, A. J.; Lindoy, L. F.; McCool, B. J.; McPartlin, M.; Tailor, B. A.; Tasker, P. A. Structure-functionrelationships in the interaction of zinc(II) and cadmium(II) with an extended range of 16-membered to 19-membered macrocycles incorporating oxygen, nitrogen, and sulfur donor atoms. Inorg. Chem. 1994, 33, 1194−1200. (9) (a) Brooker, S. Complexes of thiophenolate-containing Schiffbase macrocycles and their amine analogues. Coord. Chem. Rev. 2001, 222, 33−56. (b) Christensen, A.; Mayer, C.; Jensen, F.; Bond, A. D.; McKenzie, C. J. Controlled formation and topologies of thiophenolate-based macrocycles: rings, cylinders and bowls. Dalton Trans. 2006, 108−120. (c) Christensen, A.; Jensen, H. S.; McKee, V.; McKenzie, C. J.; Munch, M. Tsalen- and tsalpn-based nickel complexes with two aldehyde functionalities as potential synthons for thiophenolate-containing di- and polynucleating acyclic and macrocyclic ligands. Inorg. Chem. 1997, 36, 6080−6085. (d) Brooker, S.; Croucher, P. D.; Roxburgh, F. M. Controlled synthesis and reversible oxidation of a thiolate-bridged macrocyclic dinickel(n) complex. J. Chem. Soc., Dalton Trans. 1996, 3031−3037. (10) (a) Adams, H.; Bailey, N. A.; Collinson, S. R.; Fenton, D. E.; Hawley, J. C.; Kitchen, S. J. Dinuclear copper I complexes of 24membered bibracchial tetraimine Schiff base macrocycles derived from 2,5-diformylthiophene. J. Organomet. Chem. 1998, 550, 7−20. (b) Bailey, N. A.; Eddy, M. M.; Fenton, D. E.; Moss, S.; Mukhopadhyay, A. H.; Jones, G. Dinucleating macrocyclic Schiff bases derived from thiophene and their metal complexes: the crystal I

DOI: 10.1021/acs.inorgchem.9b00454 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry fluorescent/green phosphorescent anisotropic emissions. Dalton Trans. 2018, 47, 8746−8754. (b) Wu, H.; Dong, X. W.; Liu, H. Y.; Ma, J. F.; Li, S. L.; Yang, J.; Liu, Y. Y.; Su, Z. M. Influence of anionic sulfonate-containing co-ligands on the solid structures of silver complexes supported by 4,4′-bipyridine bridges. Dalton Trans. 2008, 5331−41. (23) (a) Jiang, L.; Zhang, D. Y.; Suo, J. J.; Gu, W.; Tian, J. L.; Liu, X.; Yan, S. P. Synthesis, magnetism and spectral studies of six defective dicubane tetranuclear {M4O6} (M = Ni(II), Co(II), Zn(II)) and three trinuclear Cd(II) complexes with polydentate Schiff base ligands. Dalton Trans. 2016, 45, 10233−10248. (b) Ding, Y.; Xie, Y.; Li, X.; Hill, J. P.; Zhang, W.; Zhu, W. Selective and sensitive “turn-on” fluorescent Zn2+ sensors based on di- and tripyrrins with readily modulated emission wavelengths. Chem. Commun. 2011, 47, 5431− 5433. (24) (a) Małecki, J. G.; Maroń, A. Luminescence properties of copper(I), zinc(II) and cadmium(II) coordination compounds with picoline ligands. J. Lumin. 2017, 186, 127−134. (b) Kobayashi, A.; Yoshida, Y.; Yoshida, M.; Kato, M. Mechanochromic switching between delayed fluorescence and phosphorescence of luminescent coordination polymers composed of dinuclear copper(I) iodide rhombic cores. Chem. - Eur. J. 2018, 24, 14750−14759.

J

DOI: 10.1021/acs.inorgchem.9b00454 Inorg. Chem. XXXX, XXX, XXX−XXX