Syntheses, Structures, and Properties of a Series of

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Syntheses, Structures and Properties of a Series of Polyazaheteroaromatic Core-Based Zn(II) Coordination Polymers Induced by Carboxylate Auxiliary Ligands Shui-Sheng Chen, Liang-Quan Sheng, Yue Zhao, Zhao-Di Liu, Rui Qiao, and Song Yang Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.5b01133 • Publication Date (Web): 07 Dec 2015 Downloaded from http://pubs.acs.org on December 9, 2015

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Crystal Growth & Design

Syntheses,

Structures

and

Properties

of

a

Series

of

Polyazaheteroaromatic Core-Based Zn(II) Coordination Polymers Together with Carboxylate Auxiliary Ligands Shui-Sheng Chen,*,†,‡

Liang-Quan Sheng,† Yue Zhao,*,‡ Zhao-Di Liu,†

Rui Qiao,†

and Song Yang† †

School of Chemistry and Chemical Engineering, Fuyang Normal University, Fuyang 236041, China

‡

Coordination Chemistry Institute, State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing National Laboratory of Microstructures, Nanjing University, Nanjing 210093, China

ABSTRACT:

Six Zn(II) coordination polymers [Zn(H2L)(Hipa-CH3)2]·2H2O (1),

[Zn2(HL)2(ipa-CH3)]

(2),

[Zn2(HL)2(ipa-NO2)]·2H2O

(3),

[Zn2(HL)2(ipa-NO2)]

(4),

[Zn2(HL)(BTCA)(H2O)]·H2O (5) and [Zn3(HL)3(BTCA)] (6) were synthesized by reactions of Zn(II) salts with rigid ligand 1-(1H-imidazol-4-yl)-4-(4H-tetrazol-5-yl)benzene (H2L) and different carboxylic acids of 5-methyl-isophthalic acid (H2ipa-CH3), 5-nitro-isophthalic acid (H2ipa-NO2), 1,2,4-benzenetricarboxylic acid (H3BTCA), respectively.

Complexes 1 and 2

were formed in different pH value, and 1 is one-dimensional (1D) chain extended by hydrogen bonds and π - π stacking interactions to form three-dimensional (3D) supramolecular polymer while 2 exhibits a uninodal 6-connected 3D architecture with (412·63)-pcu topology based on the binuclear Zn(II) secondary building units (SBUs). Poloymers 3 and 4 present a pair of pseudopolymorphs with layer-pillared framework. Polymer 3 possess Zn2(HL−)22+ sheet to be pillared by ipa-NO22− ligand to form 3D net while 4 build on the [Zn2(HL)(ipa-NO2)]+ layer pillared by HL− ligand. 1 ACS Paragon Plus Environment

Complex 5 is a


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(3,8)-connected tfz-d 3D net with Point (Schläfli) symbol (43)2(46·618·84) based on the tetranuclear [Zn4(COO)4] SBUs while BTCA3− ligands act as three-connector pillars to link adjacent [Zn3(HL−)3]3− layers into 3D net for 6.

Complexes 1-6 exhibit intense light blue

emission in the solid state at room temperature, and activated sample 6 shows high selective CO2 uptake over N2 and H2.

INTRODUCTION In recent years, metal-organic frameworks (MOFs) have increasingly attracted considerable attention for their charming structures and potential applications, for instance in gas absorption and separation,1-3 luminescence,4,5 catalysis,6,7 molecular magnetism,8,9 sensors,10 etc.

The assembly of MOFs can be influenced by several key factors, such as coordination

geometries of the central metals, configurations, and nature of the organic ligands11,12 as well as some external factors, such as solvent, temperature, pH value, and template effect, etc.13-16 Therefore, in order to obtain the desirable frameworks with specific structures and functions, it is important to design the organic ligands and/or regulate the synthesis conditions. realize

the

infinite

extension

of

structure,

organic

tectons

mainly

To

including

polyazaheteroaromatic ligands and multicarboxylic acids with two or more coordination atoms, such as N, O atoms, are the most widely used linkers for the assembly of various MOFs.17,18

As a consequence, most MOFs are constructed from metal ions and carboxylic

acid- or nitrogen-containing ligands.

Significantly, mixed ligands by incorporating N-donor

ligands and multicarboxylates has been proved to be effective strategy to construct intriguing MOFs due to their self-complement as acid/base or acid/acid or base/base mixed ligands.19 Generally, N-heterocyclic bridging ligands pyridine or its analogues such as pyridazine, tetrazine, triazine, and pyrazine moieties are electrically neutral,20,21 while carboxylic acid ligands are employed as Lewis acids to ligate with metal atoms by deprotonation of the

2 ACS Paragon Plus Environment

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carboxyl groups.22

Therefore, the mixed system including pyridine analogues and

carboxylate ligands are most important acid/base system employed as mixed-ligand assembly strategy due to their favorable compatibility.23,24

Apart from that, other N-heterocyclic

bridging ligands such as imidazole, tetrazole, triazole, and pyrazole moieties are electrically neutral or negatively charged by deprotonated to azolate ligands for the acidic N-H groups in the free ligand.25-29

In this sense, polyazaheteroaromatic ligands can serve not only as base

ligands , but also as acid ones because of the characteristic of deprotonation, similar to those Lewis acids possessing the carboxyl groups.

Therefore, these mixed polyazaheteroaromatic

and carboxylate ligands can be viewed as most popular acid/base or acid/acid bridging systems for preparing MOFs.19

Among the N-donors, polytopic imidazole-containing

ligands with 1H-imidazol-4-yl moieties have been intensively engaged in the formation of MOFs associated with interesting structures, topologies, and properties in our previous systematic studies.30-32 Apparently, the 1H-imidazol-4-yl groups can be electrically neutral or deprotonated to form the imidazolate anion and provide differently positioned N atoms of imidazolyl groups to connect metal atoms, possessing more flexible coordination modes. Interestingly, due their super compatibility, a series of charming complexes have been obtained

based

on

this

mixed

1,4-di(1H-imidazol-4-yl)benzene

or

Lewis

acid/base

system

1,3,5-tri(1H-imidazol-4-yl)benzene,

benzenecarboxylic acids together with varied metal salts.33,34

reactions and

of

different

As a continuation and

extension of our study, most recently we have designed a new rigid multi-nitrogen ligand containing

4-imidazolyl

and

5-tetrazolyl

groups,

namely

1-(1H-imidazol-4-yl)-4-(4H-tetrazol-5-yl) benzene (H2L), which may apparently exhibit more flexible coordination modes.

Following such a mixed ligands strategy, we carry out the

study on reactions of ligand H2L together with different carboxylate ligands and zinc salts. Herein we report the synthesis, crystal structure, fluorescence and gas adsorption properties of



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three pairs of Zn(II) complexes: [Zn(H2L)(Hipa-CH3)2]·2H2O (1) and [Zn2(HL)2(ipa-CH3)] (2),

[Zn2(HL)2(ipa-NO2)]·2H2O

(3)

and

[Zn2(HL)2(ipa-NO2)]

(4),

[Zn2(HL)2(BTCA)(H2O)]·H2O (5) and [Zn3(HL)3(BTCA)] (6) obtained by reactions of H2L and different carboxylic acids, respectively.

EXPERIMENTAL SECTION All the commercially available chemicals and solvents are of reagent grade and used as received without further purification. literature.35 Elemental

The ligand H2L was prepared according to the

Elemental analyses for C, H, and N were performed on a Perkin-Elmer 240C Analyzer

at

the

Modern

Analysis

Center

of

Nanjing

University.

Thermogravimetric analyses (TGA) were performed on a simultaneous SDT 2960 thermal analyzer under nitrogen with a heating rate of 10 ºC min-1.

FT-IR spectra were recorded in

the range of 400 - 4000 cm-1 on a Bruker Vector22 FT-IR spectrophotometer using KBr pellets.

The luminescence spectra for the powdered solid samples were measured on an

Aminco Bowman Series 2 spectrofluorometer with a xenon arc lamp as the light source.

In

the measurements of emission and excitation spectra the path width is 5 nm, and all the measurements were carried out under the same experimental conditions.

Power X-ray

diffraction (PXRD) patterns were measured on a Shimadzu XRD-6000 X-ray diffractometer with Cu Kα (λ = 1.5418 Å) radiation at room temperature.

Nitrogen (N2), carbon dioxide

(CO2) and hydrogen (H2) sorption experiments were carried out on an Autosorb-iQ gas sorption instrument in Quantachrome Instruments U.S.

The sample was activated by using

the “outgas” function of the surface area analyzer for 24 hours at 180 ºC. Preparation of [Zn(H2L)(Hipa-CH3)2]·2H2O (1).

Reaction mixture of H2L (21.2 mg,

0.1 mmol), ZnSO4·7H2O (28.7 mg, 0.1 mmol), H2ipa-CH3 (18.0 mg, 0.2 mmol) and H2O (8 mL) was adjusted to pH = 6 with 0.5 mol L-1 NaOH solution.


The mixture was then sealed

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into a 16 mL Teflon-lined stainless steel container and heated at 120 ºC for 3 days.

After

cooling to the room temperature, colorless needle crystals of 1 were collected by filtration and washed by water and ethanol for several times with a yield of 72% (48.4 mg, based on H2L). Anal. calcd for C28H26N6O10Zn (%): C, 50.05; H, 3.90; N, 12.51. Found: C, 49.82; H, 3.95; N, 12.46.

IR (KBr pellet, cm−1): 3447(m), 3130(w), 2856(w), 1703(m), 1609(m), 1569(vs),

1458(vs), 1386(s), 1299(m), 1141(s), 1069(w), 974(w), 840(m), 816(m), 776(m), 721(m), 641(m), 546(w), 483(m). Preparation of [Zn2(HL)2(ipa-CH3)] (2).

Complex 2 was obtained by the same

procedure used for preparation of 1 except that the pH value of reaction mixture was adjusted to 8 instead of 6.

After the reaction mixture was cooled down to room temperature, colorless

block crystals of 2 were collected with a yield of 66% (24.1 mg, based on H2L). Anal. Calcd for C29H20N12O4Zn2: C, 47.63; H, 2.76; N, 22.98%. Found: C, 47.45; H, 2.84; N, 22.81%. IR (KBr pellet, cm−1): 3161(m), 3106(m), 1609(s), 1577(vs), 1497(m), 1402(vs), 1347(s), 1244(w), 1165(w), 1133(m), 1078(m), 966(w), 832(m), 792(m), 768(m), 721(m), 649(m), 554(w), 459(w). Preparation of [Zn2(HL)2(ipa-NO2)]·2H2O (3).

Complex 3 was obtained by a

hydrothermal procedure as that for preparation of 2 using H2ipa-NO2 (16.6 mg, 0.1 mmol) instead of H2ipa-CH3 under DMF - H2O (1:8, v/v, 9 mL) mixed solvent system.

Colorless

needle crystals of 3 were collected in 65% yield after being washed with water and ethanol several times (25.9 mg, based on H2L).

Compound 3 can be prepared by another method.

A mixture of H2L (21.2 mg, 0.1 mmol), ZnSO4·7H2O (28.7 mg, 0.1 mmol), H2ipa-NO2 (16.6 mg, 0.1 mmol) and HCOOH (0.2 mL) was placed in a Teflon lined stainless steel vessel (12 mL) and heated at 120 °C for 72 h under Me2NH - H2O (0.3:8, v/v, 8.5 mL) mixed solvent system, and then cooled to room temperature at a rate of 5 °C/h. Colorless microcrystals of 3 were collected by filtration, washed with water and ethanol to afford 15.4 mg (39% based on



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H2L) of product.

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Anal. calcd for C28H21N13O8Zn2: C, 42.13; H, 2.65; N, 22.81%.

41.88; H, 2.79; N, 22.68%.

Found: C,

IR (KBr pellet, cm-1): 3581(w), 3154(w), 1625(vs), 1529(s),

1466(s), 1387(s), 1347(vs), 1196(w), 1173(w), 1133(m), 1078(w), 953(w), 856(s), 737(s), 641(s), 507(w). Preparation of [Zn2(HL)2(ipa-NO2)] (4).

When the same reaction stoichiometry was

used at the reaction temperature of 120 ºC for 3d, but solvothermal conditions using DMA (N, N′- dimethylacetamide) – H2O (1:5, v/v, 10 mL) as mixed solvent in stead of the mixed H2O/NaOH solution for preparation of 3, colorless block crystals of 4 were collected by filtration and washed by water and ethanol for several times with a yield of 72% (27.4 mg, based on H2L).

Compound 4 can also be prepared by the second method as that for

preparation of 3 except using CH3COOH (0.3 mL) instead of HCOOH with a yield of 54% (20.5 mg, based on H2L).


Found: C, 43.88; H, 2.42; N, 23.76%.

IR (KBr pellet, cm-1): 3304～2963(w), 2868(w),

1625(vs), 1577(m), 1537(s), 1466(s), 1363(vs), 1141(m), 1078(w), 951(w), 847(w), 832(s), 784(w), 729(s), 649(s), 554(w), 499(w). Preparation of [Zn2(HL)(BTCA)(H2O)]·H2O (5).

A mixture of H2L (21.2 mg, 0.1

mmol), ZnSO4·7H2O (57.4 mg, 0.2 mmol) and H3BTCA (21.0 mg, 0.1 mmol) in DMF - H2O (1:8, v/v, 9 mL) was sealed in a 16 mL Teflon lined stainless steel container and heated at 120 ºC for 3 d. H2L).

Colorless flake crystals of 5 were collected in 73% yield (42.7 mg, based on


2.32; N, 14.16%.

Found: C, 38.69; H,

IR (KBr pellet, cm-1): 369～2550(m), 1602(vs), 1546(vs), 1508(m),

1389(vs), 1301(m), 1188(m), 1169(m), 1131(s), 1062(w), 955(m), 861(s), 830(m), 786(s), 710(m), 648(m), 509(m). Preparation of [Zn3(HL)3(BTCA)] (6).

Complex 6 was obtained by the same

hydrothermal procedure as that for preparation of 5 except that the reaction mixture was


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heated at 180 °C. on H2L).

Colorless block crystals of 6 were collected in 75% yield (25.9 mg, based


H, 2.52; N, 24.56%.

Found: C, 44.89;

IR (KBr pellet, cm-1): 3650～2850(m), 1607(vs), 1496(m), 1461(w),

1415(m), 1353(s), 1254(w), 1131(m), 1071(w), 949(w), 850(m), 770(w), 642(m), 549(w), 480(w). Crystallography.

The crystallographic data collections for 1 - 6 were carried out on a

Bruker Smart Apex CCD area-detector diffractometer with graphite-monochromated Mo Kα radiation (λ = 0.71073 Å) using ω-scan technique.

The diffraction data were integrated by

using the SAINT program,36 which was also used for the intensity corrections for the Lorentz and polarization effects. SADABS program.37

Semi-empirical absorption correction was applied using the The structures were solved by direct methods and all the

non-hydrogen atoms were refined anisotropically on F2 by the full-matrix least-squares technique using the SHELXL-97 crystallographic software package.38 were generated geometrically.

The hydrogen atoms

The C and N atoms of the imidazole ring on 2- and

4-positions in 1 are disordered and treated by performing half-occupancies of 50 : 50%.

The

details of the crystal parameters, data collection and refinements for the complexes are summarized in Table 1, and selected bond lengths and angles with their estimated standard deviations are listed in Table S1.

RESULTS AND DISCUSSION Description of Crystal Structures.

Complex [Zn(H2L)(Hipa-CH3)2]·2H2O (1).

The

result of X-ray diffraction analysis revealed that complex 1 crystallizes in a monoclinic form with space group of P2/c (Table 1) and the asymmetric unit has a half molecule of [Zn(H2L)(Hipa-CH3)2]·2H2O, namely a Zn(II) atom sitting on a special position with a half of occupancy, half of the H2L ligand, and one partially deprotonated Hipa-CH3− ligand, one free



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water molecules.

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The partial deprotonation of H2ipa-CH3 to give Hipa-CH3− in 1 is also

confirmed by the IR spectral data of 1 since a strong band at 1703 cm-1 from -COOH was observed (see Experimental Section).

As exhibited in Figure 1a, each Zn(II) atom is

four-coordinated by two nitrogen (N1, N1A) atoms from H2L ligands and two oxygen atoms (O2, O2A) of two carboxylate groups from two Hipa-CH3−, forming distorted tetrahedral coordination geometry.

The Zn–O distances are 1.9820(14) Å while the Zn–N one is

2.0009(16) Å, and the coordination angles around the Zn1 are in the range of 95.18(8)–123.71(7)° (Table S1).

Each electrically neutral H2L ligand acts as a rod-like

bidentate tecton to link two Zn(II) atoms to form an infinite corrugated one-dimensional (1D) chain with Zn···Zn distance of 13.88 Å and Zn···Zn···Zn angle of 68.70° (Figure 1b). hydrogen

bonds

are present among carboxylate

groups,

Rich

NH or N atoms of

polyazaheteroaromatic groups and lattice water molecules (Table S2).

As a result, the 1D

chains of 1 are linked together by this set of strong hydrogen bonds to generate two-dimensional (2D) supramolecular layer (Figure 1c).

It can be seen clearly that the 2D

layers repeat in an ···ABAB··· stacking sequence along the b axis, and N−H···O, C−H···O hydrogen bonds of adjacent layers further generate a three-dimensional (3D) supramolecular framework (Figure 1d).

Particularly, the benzene ring rings from Hipa-CH3− ligands

between the adjacent 2D layers are parallel with a dihedral angle of 5.74(101)° and are separated by a centroid - centroid distance of 3.98 Å, indicating the presence of face to face π - π stacking interactions (Figure 1d).39 Crystal Structure of [Zn2(HL)2(ipa-CH3)] (2).

When the pH value of reaction system in

1 was changed from 6 to 8, a new complex 2 with deprotonated HL− and ipa-CH32− ligands was obtained different from 1.

Single-crystal X-ray diffraction analysis reveals that complex

2 crystallizes in the monoclinic space group C2/c (Table 1) with one Zn(II), one HL− and a half of ipa-CH32− in the asymmetric unit.

The crystallographically independent Zn1 shows a


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slightly distorted tetrahedral coordination geometry, being coordinated by one imidazole N atom, one tetrazole N atom from two HL− ligands and two O atoms from different ipa-CH32− (Figure 2a ).

In this complex, each ipa-CH32− ligand acts as µ4-bridge to link four Zn(II)

atoms (Type II, Scheme 2), both carboxylate groups adopting µ2-η1:η1-bridging coordination mode.

Two such carboxylate groups from different ipa-CH32− ligands bridge two Zn(II)

atoms to give a binuclear [Zn2(COO)2] motif, with the Zn···Zn distance of 3.45 Å . Meanwhile, each Zn2(COO)2 binuclear unit links four HL− and two ipa-CH32− ligands to form a 6-connected node as secondary building unit (SBU) (Figure S1).

As for the HL− and

ipa-CH32−, both of them act as µ2-bridges linking two neighboring Zn2(COO)2 units to form 3D framework (Figure 2b), topologically, they can be considered as 2-connected nodes and not counted as node. Topological analysis using the TOPOS software40,41 indicates that complex 2 exhibits a uninodal 6-connected 3D architecture with (412·63)-pcu topology (Figure 2c).42,43 Crystal Structure of [Zn2(HL)2(ipa-NO2)]·2H2O (3).

When the auxiliary ligand of

H2ipa-CH3 in 2 was changed to H2ipa-NO2 with electron-withdrawing nitro substituent, complex 3 with a different structure was obtained.

Complex 3 crystallizes in the triclinic

P-1 space group and its asymmetric unit contains two Zn(II) atoms, two different deprotonated HL− ligands, one ipa-NO22− and two free water molecules. As shown in Figure 3a, both of the Zn(II) atoms adopt the same 4-coordinated tetrahedral coordination geometry with a N3O donor set defined by three nitrogen atoms from three different HL− and one oxygen atom from one distinct ipa-NO22− ligand.

The Zn–N distances range from 1.970(2)

to 2.079(2) Å, the Zn–O average distance is 1.937(17) Å, and the coordination angles around Zn(II) vary from 93.61(9)° to 128.85(9)° (Table S1).

It is noteworthy that the H2L ligands

are deprotonated to give HL− with different coordination modes in 2 (Type III and IV, Scheme 1), and these two kinds of anion ligands link the Zn(II) centers into a 2D Zn2(HL−)22+



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Page 10 of 39

double layer, where all Zn(II) atoms and HL− linkers act as 3-connected nodes (Figure 3b). On the other hand, ipa-NO22− ligands employ as two-connector pillars to link Zn(II) atoms of adjacent 2D nets to form 3D frameworks using its two terminal carboxylate groups with µ1-η1:η0-monodentate coordination mode (Type III, Scheme 2).

The 3D framework can also

be viewed to be a layer-pillared net, where the layer is a Zn2(HL−)22+ sheet and the pillar is a ipa-NO22− ligand.

As discussed above, the ipa-NO22− ligands ligate to Zn2(HL−)22+ sheets

via both Zn-O contacts, therefore the 3-connected Zn node in the 2D net is extended to be a 4-connected node in the layer-pillared framework (Figure 3c). Crystal Structure of [Zn2(HL)2(ipa-NO2)] (4). When the mixed solvent of H2O/DMA was utilized in place of the system of H2O/DMF under similar synthetic conditions in 3, a different structure was formed for 4.

The compounds of 3 and 4 can be classified as a pair of

supramolecular isomers, due to the same framework formula except the additional lattice water molecules in 3.

However, the structures of 3 and 4 are absolutely different.

crystallizes in monoclinic space group P-1 while 4 is in monoclinic space group P21/c.

3 As

shown in Figure 4a, each of the two crystallographically different Zn(II) atoms is four-coordinated with distorted tetrahedral coordination geometry defined by three nitrogen atoms from three different HL− and one oxygen atom from one ipa-NO22− ligand.

The Zn–N

and Zn–O bond lengths and coordination angles around the Zn(II) are in the normal range as listed in Table S1.

The HL− ligands in 4 have two different coordination modes III and IV,

as shown in Scheme 1.

If the linkage of HL− ligand with mode III is neglected, the Zn1 and

Zn2 are linked by HL− ligands with mode IV together with ipa-NO22− ligands to generate a 2D network (Figure 4b, left).

The partially deprotonated HL− ligand in 4 also employs a

µ3-bridge by means of the heterocyclic nitrogen atoms (Type III, Scheme 1) to link Zn(II) atoms of adjacent 2D nets to form 3D frameworks in the ab plane (Figure 4c). Topologically, the 2D net is described by the fes 4·82 net,44 where both of the Zn(II) atoms


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and HL− linkers act as 3-connected nodes (Figure 4b, right).

The 3D framework can also be

viewed to be a layer pillared net, where the layer is a fes 4·82 sheet and the pillar is the µ3-HL− ligands.

As discussed above, the µ3-HL− ligands ligate to fes 4·82 sheets via Zn–N

contacts, therefore two 3-connected Zn nodes in the fes net are extended to be 4-connected nodes in the layer pillared framework. Crystal Structure of [Zn2(HL)(BTCA)(H2O)]·H2O (5).

To further investigate the effect of

multi-carboxylate ligands, the former dicarboxylic acid was changed to 1, 2, 4-benzenetricarboxylic acid, and a new complex 5 with a different structure was obtained. The result of X-ray crystallographic analysis revealed that there is two Zn(II) atoms, one HL−, one complete deprotonated BTCA3− ligand, one coordinated and one free water molecules in the asymmetric unit.

As shown in Figure 5a, Zn1 with a N2O3 donor set, adopts a distorted

square-pyramidal coordination geometry by the coordination of three carboxylate O atoms from two BTCA3− ligands, and two N atoms from two HL− ligands while Zn2 is four-coordinated by one N atom from one HL− ligand and two O atoms from two BTCA3− and one water molecule to form a distorted tetrahedral coordination geometry.

The tetrazole

group of HL− utilizes two N atoms to ligate two Zn(II) atoms in µ2-N1, N4 coordination mode while the 4-imidazole group links one Zn(II) atom by outer N1-position atom (Type III, Scheme 1).

Each BTCA3− in 5 acts as a µ4-bridge to link four Zn(II) atoms with both

adjacent carboxylate groups adopting µ2-η1:η1-bis-monodentate and the third adopting µ1-η1:η0-monodentate coordination modes, respectively (Type V, Scheme 2).

Particularly,

the adjacent carboxylate groups of two BTCA3− ligands bridge four Zn(II) atoms to form tetranuclear [Zn4(COO)4] SBU if ignoring the Zn-O linkage from the third µ1-η1:η0 carboxylate group of BTCA3−, which are connected together by HL− ligands to generate a 2D network (Figure 5b, left).

From the perspective of topology, the [Zn4(COO)4] SBU can be

regarded as a 6-connector and each HL− ligand as a 3-connector in the 2D layer. As a result,



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Page 12 of 39

the 2D layer is a 2-nodal (3, 6)-connected 2D kgd net with the Point (Schläfli) symbol of (43)2(46·66·83) (Figure 5b, right).45

The 2D networks are further linked by the just neglected

Zn-O linkage to generate a 3D framework structure (Figure 5c). was carried out to get insight of the structure of 5.

The topological analysis

As mentioned above, each HL− ligand is

neighbored by three [Zn4(COO)4] SBUs which can be viewed as a 3-connector. Meanwhile, each [Zn4(COO)4] SBU can be regarded as a 8-connected node because it links six HL− ligands and two [Zn4(COO)4] SBUs (Figure S2).

Thus, the resulting structure of 5 is a (3,

8)-connected binodal 3D net with stoichiometry of (3-c)2(8-c), as shown in Figure 5d.

The

Point (Schläfli) symbol for the net is (43)2(46·618·84), which has been referred by O’Keeffe and Wells to the tfz-d notation.46 Crystal Structure of [Zn3(HL)3(BTCA)] (6).

When the reaction temperature is changed to

180 °C in the reaction system of 5, a new complex 6 with a different structure was isolated. Compound 6 crystallizes in the triclinic space group P-1, and the asymmetric unit contains three unique Zn(II) atoms, three distinct HL− ligands and one BTCA3−.

As shown in Figure

6a, each of the three crystallographically unique Zn(II) atoms is four-coordinated with distorted tetrahedral coordination geometry defined by three N atoms from three different HL− and one O atom from the distinct BTCA3− ligand.

The Zn–O and Zn–N bond lengths

and coordination angles around the Zn(II) are in the normal range as listed in Table S1. Different from the complex 5, as a multidentate group, the tetrazole fragment flexibly utilizes different positions of 1, 3- / 1, 4-N atoms in µ2-N1, N3 and µ2-N1, N4 coordination modes to ligate two Zn(II) atoms (Type III and IV, Scheme 1) while the neutral imidazole group links one Zn(II) atom, therefore, three different HL− ligands act as 3-connected nodes to bridge Zn(II) atoms, forming 2D double-layer network (Figure 6b). completely

deprotonated

BTCA3−

ligands

use

three

Different from 5, the carboxylate

groups

in

µ1-η1:η0-monodentate monodentate coordination mode to connect three Zn(II) atoms (Type VI,


Page 13 of 39

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Scheme 2).

In this sense, BTCA3− ligands act as three-connector pillars to link adjacent 2D

[Zn3(HL−)3]3− nets to form 3D pillar-layered frameworks, showing channels with a pore diameter approximately 5.2 Å (considering van der Waals radii) viewed along a axis (Figure 6c).

The total void value of the channel is estimated (by PLATON)47 to be 512.7 Å3, 21.6%

of the total crystal volume of 2369.0 Å3 and the pore surface is decorated with rich uncoordinated tetrazole-N atoms pointing to the 1D channels along with accessible void (Figure S3). Synthesis of the Complexes and Comparison of the Structures.

Complexes 1–6,

prepared by reactions of mixed N-donor ligands and multicarboxylates together with ZnSO4·7H2O under different reaction systems such as pH value, solvent systems, reaction temperature.

The difference between 1 and 2 is ascribed to the different reaction pH leading

to the partial (in 1) and complete deprotonation (in 2) of the H2ipa-CH3 ligand (vide supra). The results imply that reaction pH is important in determining the structure of the complexes. The different solvent systems of DMF/H2O and DMA/H2O regulate the formation of supramolecular isomers 3 and 4, which may suggest the hydrolysis product of HCOO-/Me2NH2+ or CH3COO-/Me2NH2+ generated from in situ hydrolysis of DMF or DMA may act as structure-directing agents to induce the formation of 3 and 4.14

To explain the

formation mechanism for isomers 3 and 4, we have tried to synthesize these compounds in aqueous solution by direct reactions of ZnSO4, H2L, H2ipa-NO2 ligands, HCOOH (CH3COOH), and Me2NH (see experimental). The polymers of 3 and 4 were obtained from respective system, which suggests the hydrolysis product from DMF or DMA can influence the products by the template effect.15,16

Meanwhile, polymers of 5 and 6 are obtained under

different reaction temperature, indicating the fact that temperature can effectively control the topology and dimensionality of the frameworks by thermal desolvation and changing the coordination modes.48,49

Higher temperature may bring a different coordination



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Page 14 of 39

environment of Zn2+ ion by removing the coordinated water molecule in 5 and lead to more complicated 3D network for 6.

Taking the property of the ligands into consideration, ditopic

tetrazolate and 4-imidazolate-containing ligand can be deprotonated to give HL− or L2− thus possessing one to six potential binding sites while H2ipa-CH3, H2ipa-NO2 and H3BTCA in this paper easily deprotonate to be divalent or trivalent carboxylic acid ions.

Therefore, different

molar ratio products of Zn2+/HL− (L2−)/ ipa-CH32− (ipa-NO22−) (BTCA3−) can be probably generated according to charge balance principle.

Authough different molar ratio of reactants

was modulated in the preparation process, the resulting ratio components are fixed as appeared in the products of 1 - 6.

In addition to act as a neutral ligand to utilize differently

positioned N atoms of heterocyclic rings to ligate Zn(II) atoms in 1(Types I, Scheme 1), compound H2L can mainly serve as a three-connector in the case of the deprotonation of the tetrazolyl group to give the tetrazolate anion participating in the construction of 3 - 6 (Types II, III and IV, Scheme 1).

The results further confirm that the versatile coordination modes

of H2L can effectively tune the fine structure in need of the requirement of coordination geometries of metal ions.

Thus, three pairs of Zn(II) complexes have been successfully

constructed based on the mixed self-complement as Lewis acid/base or acid/acid systems by incorporating N-donor ligands and multicarboxylates as auxiliary linkers.

The difference

between two pairs of 1, 2 and 3, 4 is ascribed to meta-positioned substituents of isophthalates that different steric and electronic nature on the aromatic backbone of isophthalate could significantly affect the binding modes of carboxylates upon metal coordination, ranging from monodentate, chelating, to bridging.50,51

Complex 1 exhibits 1D chain with terminal

partially deprotonated Hipa-CH3− ligand, but binuclear [Zn2(COO)2] motifs based on completely deprotonated ipa-CH32− were extended by neutral H2L to form 3D network with pcu topology in 2.

Complexes 3 and 4 present a pair of pseudopolymorphs regulated by

different solvent systems, and both of 3 and 4 belong to layer-pillared framework.


The

Page 15 of 39

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ipa-NO22− ligand pillar the Zn2(HL−)22+ sheet, into the 3D net in 3 while polymer 4 possess the layer-pillared framework with [Zn2(HL)(ipa-NO2)]+ layer and HL− pillar.

H3BTCA has

one more carboxylate group in an adjacent position of isophthalate to participate in coordination to make another pair of new polymers of 5 and 6, different with aforementioned dicarboxylic

acid.

The

adjacent

carboxylate

groups

from

BTCA3-

adopt

µ2-η1:η1-bis-monodentate in 5 and µ1-η1:η0-monodentate coordination mode in 6 respectively. It is noteworthy that the adjacent carboxylate groups of two BTCA3− ligands bridge four Zn(II) atoms to form tetranuclear [Zn4(COO)4] SBU in 5, which are further linked into a 3D framework by the third carboxylate group with µ1-η1:η0-monodentate coordination mode. Compared with polymer 5, three carboxylate groups of BTCA3- in 6 coordinate with Zn(II) atoms to form tetra nodes rather than the tetranuclear building unit as 5.

The 2D Zn3(HL)33+

layers are pillared into 3D pillar-layered net by HL− ligand for 6. Thermal

Stabilities

and

Powder

X-ray

Diffraction

of

the

Complexes.

Thermogravimetric (TGA) analysis of complexes 1−6 were carried out under a N2 atmosphere from 25 to 700 °C, in order to understand the behavior of the guest molecules of the compounds with respect to heating and structures decomposition information of the skeletons (Figure S4).

For 1, the first weight loss of 5.32% in 130–180 ºC indicates the exclusion of

one lattice water molecules (calc. 5.37%), and the decomposition of the residue occurred at 260 ºC.

No obviously weight loss were found for complexes 2, 4 and 6 before the

decomposition of the frameworks occurred at about 370, 390 and 375ºC respectively, which are in good agreement with the results of the crystal structures. Complex 3 shows a weight loss of 4.42% in the temperature range of 145–205 ºC corresponding to the release of lattice water molecules (calc. 4.51%) and pyrolysis of the residue occurs at 405 ºC with consecutive weight losses, which did not stop until heated to 700 ºC.

The TGA curve for 5 displays

weight losses of 6.31% at 210 ºC, suggesting the loss of the corresponding water molecules



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(calc. 6.15%), and the framework of 5 is stable up to 360 ºC.

Page 16 of 39

The pure phase of the

complexes was proved by the powder X-ray diffraction (PXRD), where the patterns of as-synthesized 1 - 6 are consistent with the corresponding simulated ones (Figure S5). According to the stability information from the TGA curves, the porous sample of 6 was activated at optimized temperature 180 ºC in order to make gas adsorption.

The PXRD

patterns at varied temperature show that the porous framework of 6 is retained (Figure S5), indicating that complex 6 has permanent porosity after activation at 180 ºC. Luminescent

Properties.

Inorganic–organic

hybrid

coordination

complexes,

constructed by d10 metal centers and conjugated organic linkers, are promising candidates for photoactive materials owing to their potential applications as chemical sensors and photochemistry.52

The fluorescence properties of the stable materials 1−6, as well as free

H2L ligand have been investigated in the solid state at room temperature, as depicted in Figure 7.

The free H2L ligand shows intense emission band at 385 nm upon excitation at 338 nm,

which may be attributed to π*→π transition of the intraligands.53,54

As previously

reported,55,56 solid-state benzene-carboxylate ligands can also exhibit fluorescence at room temperature, and the emission bands of these ligands can be assigned to the π* → n transition. Fluorescent emission of benzene-dicarboxylate ligands resulting from the π* → n transition is very weak compared with that of the π* → π transition of the H2L ligand, so benzene-carboxylate ligands almost have no contribution to the fluorescent emission of as-synthesized coordination polymers.57,58

On complexation of these ligands with Zn(II)

atoms, excitation of the microcrystalline samples leads to the generation of strong broad blue fluorescent emissions, with the maximal peaks occurring at 418 nm (λex = 385 nm) for 1, 454 nm (λex = 379 nm) for 2, 453 nm (λex = 372 nm) for 3, 456 nm (λex = 376 nm) for 4, 448 nm (λex = 373 nm) for 5, and 449 nm (λex = 372 nm) for 6.

In contrast to the case for the free

H2L ligand, the emission bands of complexes 1 - 6 red-shifted ranging from 33 to 69 nm.


Page 17 of 39

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Such board emission bands of the complexes mainly originate from ligand-based luminescence, corresponding shifts originated from ligand-to-metal charge transfer.59,60

In

addition, it is noteworthy that the enhancement of luminescence for the complexes 1 - 6 compared with the free ligand under the same conditions may mainly originate from the coordination interactions between the metal Zn(II) atom and the ligand, which enhanced its conformational rigidity and then decreased the nonradiative energy loss.61,62 Gas Sorption Properties.

As discussed above, the framework 6 can maintain its

porous framework as evidenced by PXRD patterns at varied temperature (Figure S5), thus gas adsorption property of porous material can be expected.

The N2, CO2 and H2 adsorption

isotherms for the porous materials 6 are shown in Figures 8 and 9.

It can be seen that no N2

uptake was observed at 77 K in the low-pressure region, and only shows 45.64 cm3/g at 1 atm, which exhibits type III sorption profiles, suggesting that only surface adsorption occurs (Figure 8).63,64

Similarly, no H2 adsorption was observed in Figure 8. The CO2 adsorption

isotherm of 6 displays a steep rise at the relative low pressure region which can be categorized as reversible type-I, exhibiting a typical permanent microporosity (Figure 8).

Porous 6

adsorbs CO2 up to 15.32 wt% (78.11 cm3 g-1 at STP, 3.49 mmol g-1) at 195 K corresponding to 3.62 CO2 molecules per formula unit.

The Langmuir and BET surface areas of 6

estimated from the CO2 adsorption isotherm are 452 and 336 m2 g-1, respectively.

Due to the

exceptional adsorption capacity for CO2 and high selectivity for CO2 over N2 and H2, we made further study for the sorption capacity of 6 around ambient temperature to estimate its potential application in capturing the greenhouse gas CO2 in normal conditions.

It is notable

that 6 also shows good CO2 adsorption capacity even at ambient temperature.

6 can store

CO2 gas up to 7.46 wt% (37.96 cm3 g-1 at STP), at 273 K and 1 atm, and 4.71 wt% (23.99 cm3 g-1 at STP) at 298 K and 1 atm, comparable to the reported literature (Figure 9).65 Additionally, almost no N2 adsorption was observed at room temperature.


The selective


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Page 18 of 39

adsorption for CO2 may be associated with the fact that the host framework of 6 decorated with electron-rich system of tetrazole groups may give rise to an electric field (Figure S3), inducing a dipole in CO2,66,67 and the exposed uncoordinated nitrogen atoms may further contribute to the adsorption potential energy.68,69

The enthalpy of CO2 adsorption was

calculated using a variant of the Clausius–Clapeyron equation,70 and used to evaluate the adsorption selectivity for CO2 over N2.

The adsorption enthalpy of 33.90 kJ mol-1 at zero

coverage (Figure 10), and Qst slightly decreases and approaches a value of 28.95 at 4.9 mmol g−1 with the CO2 loading increasing, higher than the values of silicious zeolite (27 kJ mol-1),71 but lower than the amine-functionalized MMOFs,72,73 which further verify extremely favorable host–guest interactions.

The high Qst further indicates that the uncoordinated N

atoms from N-rich tetrazole rings may act as Lewis base sites and have a positive effect on the adsorption of CO2 by facilitating dipole–quadrupole interactions between the framework pores surfaces decorated with uncoordinated N atoms and CO2 molecules.74-78

The ratios of

the initial slopes of the CO2 and N2 adsorption isotherms were used to estimate the adsorption selectivity for CO2 over N2 (Figures S6 and S7).79

From the calculated CO2/N2 selectivity of

36 at 273 K and 23 at 298 K, it suggests that 6 may be potentially used to selectively adsorb CO2 over N2 in ambient temperature.80,81

CONCLUSION Six Zn(II) coordination complexes with diverse structures were successfully constructed from mixed ligands incorporating N-donor ligands and multicarboxylates together with Zn(II) salts by hydrothermal method under different reaction conditions.

The results of present

work further illustrate that multi N-donor and multicarboxylates ligands can be favorable self-complement as acid/base or acid/acid mixed ligands and effective building blocks in construction of coordination frameworks because of their super compatibility.


The

Page 19 of 39

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complexes 1 - 6 with high stability exhibit photoluminescence properties and activated porous material 6 exhibits high selective CO2 uptake over N2 and H2. Significantly, 6 may be potentially used to selectively adsorb CO2 over N2 in ambient temperature.

Introduction of

functional groups into MOFs by using some N-rich auxiliary ligands has been further demonstrated to be a reasonable strategy for the construction of targeted porous MOFs for CO2 capture and separation.

ASSOCIATED CONTENT Supporting Information.

X-ray crystallographic file in CIF format, selected bond lengths

and angles (Table S1), hydrogen bonding data (Table S2), structure illustrations for complexes 2, 5 and 6 (Figures S1, S2 and S3), TGA (Figure S4), PXRD data (Figure S5) and the fitting initial slope for CO2 and N2 isotherms (Figures S6 and S7).

This material is available free of

charge via the Internet at http://pubs.acs.org.

AUTHOR INFORMATION Corresponding Author * Fax: 86 558 2595626.

Tel: 86 558 2595626.

E-mail: [email protected]

* Fax: 86 25 8359 7300.

Tel: 86 25 8359 7300.

E-mail: [email protected]

ACKNOWLEDGEMENT This work was financially supported by the National Natural Science Foundation of China (Grant no. 21171040 and 21401099).

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(61) Zhang, L. Y.; Zhang, J. P.; Lin, Y. Y.; Chen, X. M. Cryst. Growth Des. 2006, 6, 1684. (62) Li, X.; Wang, X. W.; Zhang, Y. H. Inorg. Chem. Commun. 2008, 11, 832. (63) Qiao, R.; Chen, S. S.; Sheng, L. Q.; Yang, S.; Li, W. D. J. Solid. State. Chem. 2015, 228, 199. (64) Chen, M. S.; Chen, M.; Okamura, T.-a.; Sun, W. Y.; Ueyama, N. Microporous Mesoporous Mater. 2011, 139, 25. (65) Chen, Y. Q.; Qu, Y. K.; Li, G. R.; Zhuang, Z. Z.; Chang, Z.; Hu, T. L.; Xu, J.; Bu, X. H. Inorg. Chem. 2014, 53, 8842. (66) Zou, Y.; Hong, S.; Park, M.; Chun, H.; Lah, M. S. Chem. Commun. 2007, 5182. (67) Nakagawa, K.; Tanaka, D.; Horike, S.; Shimomura, S.; Higuchia, M.; Kitagawa, S. Chem. Commun. 2010, 46, 4258. (68)Lin, J. B.; Zhang, J. P.; Chen, X. M. J. Am. Chem. Soc. 2010, 132, 6654. (69) Vaidhyanathan, R.; Iremonger, S. S.; Dawson, K. W.; Shimizu, G. K. H. Chem. Commun. 2009, 3, 5230. (70) Dincă, M.; Long, J. R. J. Am. Chem. Soc. 2005, 127, 9376. (71) Dunne, J. A.; Rao, M.; Sircar, S.; Gorte, R. J.; Myers, A. L. Langmuir 1996, 12, 5896. (72) Mondal, S. S.; Bhunia, A.; Baburin, I. A.; Jäger, C.; Kelling, A.; Schilde, U.; Seifert, G.; Janiak, C.; Holdt, H. J. Chem. Commun. 2013, 49, 7599. (73) Sumida, K.; Rogow, D. L.; Mason, J. A.; McDonald, T. M.; Bloch, E. D.; Herm, Z. R.; Bae, T.-H.; Long, J. R. Chem. Rev. 2012, 112, 724. (74) Vaidhyanathan, R.; Iremonger, S. S.; Shimizu, G. K. H.; Boyd, P. G.; Alavi, S.; Woo, T. K. Science 2010, 330, 650. (75) Chen, D. M.; Xu, N.; Qiu, X. H.; Cheng, P. Cryst. Growth Des. 2015, 15, 961. (76) Nagaraja, C. M.; Haldar, R.; Maji, T. K.; Rao, C. N. R. Cryst. Growth Des. 2012, 12, 975. (77) Chen, D. M.; Xu, N.; Qiu, X. H.; Cheng, P. Cryst. Growth Des. 2015, 15, 961. (78)


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Khutia, A.; Janiak, C. Dalton Trans. 2014, 43, 1338. (79) An, J.; Geib, S. J.; Rosi, N. L. J. Am. Chem. Soc. 2010, 132, 38. (80) Liang, Z.; Du, J.; Sun, L.; Xu, J.; Mu, Y.; Li, Y.; Yu, J.; Xu, R. Inorg. Chem. 2013, 52, 10720. (81) Chen, D. M.; Zhang, X. P.; Shi, W.; Cheng, P. Cryst. Growth Des. 2014, 14, 6261.



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Table 1. Crystal Data and Structure Refinements for Complexes 1 - 6 1

2

3

Empirical formula

C28H28N6O10Zn

C29H20N12O4Zn2

C28H21N13O8Zn2

Formula weight

673.90

731.31

798.30

Temperature / K

296(2)

296(2)

296(2)

Crystal system

Monoclinic

Monoclinic

Triclinic

Space group

P2/c

C2/c

P-1

a /Å

11.791(2)

10.0730(8)

11.3215(6)

b /Å

8.6833(15)

15.3922(13)

11.5971(6)

c /Å

15.668(3)

17.9769(15)

12.8095(6)

α /°

90.00

90.00

89.4670(10)

β /°

106.991(3)

91.140(2)

70.064(2)

γ /°

90.00

90.00

73.5360(10)

V (Å3)

1534.1(5)

2786.7(4)

1509.10(13)

Z

2

4

2

Dc (g cm-3)

1.459

1.743

1.752

F(000)

696

1480

804

θ range /°

2.35 - 24.99

2.27 – 27.55

1.84 - 27.55

Reflns. Collected

8116

9339

18932

Independent reflns.

2683

3189

6900

Goodness-of-fit

1.079

1.124

1.011

R1a (I > 2σ (I))

0.0308

0.0251

0.0312

wR2b (I > 2σ (I))

0.0852

0.0723

0.0960


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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


4

a

5

6

Empirical formula

C28H17N13O6Zn2

C19H14N6O8Zn2

C39H24N18O6Zn3

Formula weight

762.29

585.10

1036.87

Temperature / K

296(2)

293(2)

296(2)

Crystal system

Monoclinic

Triclinic

Triclinic

Space group

P21/c

P-1

P-1

a /Å

14.1568(10)

10.695(2)

11.242(5)

b /Å

26.1748(18)

10.871(2)

15.741(7)

c /Å

8.8343(6)

11.086(2)

16.186(7)

α /°

90.00

79.97(3)

115.215(7)

β /°

107.3110

62.28(3)

101.661(7)

γ /°

90.00

69.00(3)

103.396(6)

V (Å3)

3125.3(4)

1065.2(4)

2369.0(17)

Z

4

2

2

Dc (g cm-3)

1.620

1.818

1.454

F(000)

1536

584

1044

θ range /°

1.56 - 27.51

2.01 - 25.01

1.48 - 25.01

Reflns. Collected

20709

5946

12369

Independent reflns.

7150

3727

8248

Goodness-of-fit

1.089

1.010

1.028

R1a (I > 2σ (I))

0.0404

0.0646

0.0822

wR2b (I > 2σ (I))

0.1124

0.1615

0.2084

R1 =Σ||Fo| - |Fc||/Σ|Fo|.

+(aP)2+bP].

b

wR2 = |Σw(|Fo|2 - |Fc|2)|/Σ|w(Fo)2|1/2, where w = 1/[σ2(Fo2)

P = (Fo2 + 2Fc2)/3.

27 Environment ACS Paragon Plus


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Captions for figures and scheme: Scheme 1.

Coordination modes of H2L ligand appeared in complexes 1–6.

Scheme 2. Coordination modes of H2ipa-CH3, H2ipa-NO2, H3BTCA ligands appeared in complexes 1–6. Figure 1 (a) The coordination environment of Zn(II) atom in 1 with the ellipsoids drawn at the 30% probability level. The hydrogen atoms and free water molecule are omitted for clarity. Symmetry Code: A 2-x, y, 0.5-z, B 2-x, -y –z. (b) The 1D chain formed by Zn(II)/H2L with terminal Hipa-CH3− ligands. (c) The packing diagram of 2D layer linked by hydrogen bonds in 1. (d) The 3D framework of 1 packed by hydrogen bonds and π-π stacking interactions: different colors for different 2D layers. Figure 2 (a) The coordination environment of Zn(II) atoms in 2 with the ellipsoids drawn at the 30% probability level. The hydrogen atoms omitted for clarity. Symmetry Code: A 1.5-x, 0.5+y, 1.5-z, B 1-x, 2-y, 1-z, C 1-x, y, 0.5-z. (b) The 3D framework of 2. (c) Schematic representation of the pcu topology of 2. Figure 3 (a) The coordination environment of Zn(II) atom in 3 with the ellipsoids drawn at the 30% probability level. The hydrogen atoms and free water molecules are omitted for clarity. Symmetry Code: A 1+x, y, z, B 1+x, y, -1+z, C 1-x, 1-y, 2-z, D 2-x, 2-y, 1-z. (b) The 2D double layer of Zn2(HL−)22+. (c) 3D framework of 3 constructed from 2D networks pillared by ipa-NO22− ligands. Figure 4 (a) The coordination environment of Zn(II) atom in 4 with the ellipsoids drawn at the 30% probability level. The hydrogen atoms are omitted for clarity. Symmetry Code: A -x, 1-y, 1-z, B -x, 1-y, -z, C 1+x, 0.5-y, -0.5+z, D 1+x, y, -1+z. (b) The 2D double-layer framework (left), simplified 2D fes net (right). (c) 3D structure of 4 constructed from 2D


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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


networks pillared by HL− ligands. Figure 5 (a) The coordination environment of Zn(II) atom in 5 with the ellipsoids drawn at the 30% probability level. The hydrogen atoms and water molecule are omitted for clarity. Symmetry Code: A -1-x, 1-y, 1-z, B 1-x, -y, -z, C 1-x, 1-y, -z, D -1+x, 1+y, 1+z. (b) 2D layer structure of 5, tetranuclear [Zn4(COO)4] SBUs highlighted by the green circle (left) and simplified (3, 6)-connected 2D kgd net (right). (c) 3D framework of 4: different colors for different 2D layers. (d) Schematic representation of the 3D tfz-d net of 5 with (43)2(46·618·84) topology: pink, [Zn4(COO)4] SBUs; green, HL− ligands. Figure 6 (a) The coordination environment of Zn(II) atoms in 6 with the ellipsoids drawn at the 30% probability level. The hydrogen atoms are omitted for clarity. Symmetry Code: A 1+x, 1+y, 1+z, B 2-x, 2-y, 1-z, C 1+x, y, z, D 1-x, 1-y, 1-z. (b) The 2D double layer of [Zn3(HL−)3]3−. (c) 3D framework of 6 constructed from 2D networks pillared by BTCA3− ligands. Figure 7 Emission spectra of H2L and complexes 1 - 6. Figure 8 Gas sorption isotherms of 6: CO2 (■) at 195 K, N2 (▲) and H2 (◆) at 77 K. Filled symbols: adsorption; open symbols: desorption. Figure 9 Gas sorption isotherms of 6: CO2 (■) at 273 and 298 K; N2 (▲) at 273 and 298 K. Filled symbols: adsorption; open symbols: desorption. Figure 10 CO2 adsorption enthalpy for 6 calculated from the CO2 adsorption isotherms at 273 and 298 K.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Scheme 1

Scheme 2


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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(a)

(d) Figure 1



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(a)

(b)

(c) Figure 2


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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(a)

Figure 3



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(a)

Figure 4


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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(a)

Figure 5



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(a)

Figure 6


Page 36 of 39

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H2L

Relative Intensity

1 2 3 4 5 6

300

350

400

450

500

550

600

650

Wavelength/nm

Figure 7

Vads/cm3g-1(STP)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


80

CO2 at 195K 60

40

N2 at 77K

20

0

H2 at 77K 0.0

0.2

0.4

0.6

0.8

P/atm

Figure 8


1.0


Vads/cm3g-1(STP)

40

CO2 at 273K

30

20 CO2 at 298K

10 N2 at 273K N2 at 298K

0 0.0

0.2

0.4

0.6

0.8

1.0

P/atm

Figure 9

40

∆ Hads (KJ/mol)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 38 of 39

30

20

10

0 0

1

2

3

4

CO2 adsorbed (wt %)

Figure 10


5

Page 39 of 39

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


For Table of Contents Use Only

Syntheses,

Structures

and

Properties

of

a

Series

of

Polyazaheteroaromatic Core-Based Zn(II) Coordination Polymers Together with Carboxylate Auxiliary Ligands Shui-Sheng Chen, Liang-Quan Sheng, Yue Zhao, Zhao-Di Liu, Rui Qiao, and Song Yang

Three pairs of Zn(II) coordination polymers have been obtained based on mixed ligands incorporating N-donor and carboxylates together with Zn(II) salts by hydrothermal method under variable reaction conditions. adsorption properties of the compounds have also been explored.


Fluorescence and gas

Syntheses, Structures, and Properties of a Series of

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