English

• 0.   Introduction

  Nowadays, due to the rapid development of industry and agriculture, the emission of a large number of toxic and harmful substances has gradually increased, which has become an urgent problem facing the world^[1]. These highly soluble and mobile substances can easily diffuse into the atmosphere, land, and water, leading to serious threats to ecosystems^[2]. According to the types of pollutant pollution, it can be roughly divided into water pollution, air pollution, and soil pollution^[3]. Pollutants in the natural environment mainly include inorganic anion and cation pollutants (such as Fe³⁺, Hg²⁺, and chromium salts), organic pollutants (insecticides, herbicides, fungicides, etc.), nitroaromatic compounds produced in the chemical process, various phenols, aniline compounds, volatile organic compounds, nitrogen oxides, and sulfur compounds^[4].

  Phenols are common organic pollutants in the environment, mainly from industrial wastewater such as oil refining, papermaking, and chemical industry^[5]. Phenolic substances are mostly used in the preparation of pesticides. Due to the excessive use of pesticides, phenolic substances generally exist in groundwater and soil. It can migrate, adsorb, and accumulate in the soil through irrigation and rainwater scouring, thus seriously affecting the environment, and enter the human body through the food chain, accumulate in the human body, and then cause certain harm to the human body^[6-7]. Phenol is a highly toxic class and has been listed as a key organic pollutant by many countries in the world. When humans ingest a certain amount of phenolic substances, there will be poisoning symptoms, such as vertigo, anemia, and other neurological symptoms^[8].

  Antibiotics are secondary metabolites or synthetic analogues produced by microorganisms in metabolic activities^[9]. Since 1946, Moore reported that antibiotics can promote the growth of broilers and improve disease resistance. The types and usage of antibiotics in the breeding industry have gradually increased, and gradually have a great impact on human and animal diseases^[10]. However, due to the interesting relationship, antibiotics are overused, which reduces the metabolic capacity of organisms to antibiotics, and its biodegradation rate is also very low. It is easy to cause the gradual accumulation of antibiotics in the human body, thus enhancing the resistance of bacteria^[11]. When humans ingest foods containing antibiotics, they will not only cause health risks such as toxic side effects and resistance, but also cause the production of antibiotic resistance bacteria (ARB) and antibiotic resistance genes (ARGs) in water bodies, and enter the aquatic ecosystem with the discharge of excrement, causing a series of environmental health problems^[12].

  Aniline is an important chemical raw material and intermediate. It is widely used in dyes, mines, pharmaceuticals, plastics, and other industries^[13]. Its toxicity is extremely strong, as long as a little can make people poisoned, there will be hemolytic anemia, liver damage, and the formation of toxic liver disease, some of which have significant carcinogenic, teratogenic, and mutagenic effects, causing certain harm to the human body^[14]. Due to the strong polarity of aniline substances, they are easily soluble in water, thus entering the environmental water body, which seriously affects the natural environment.

  At present, the detection methods of common pollutants in the environment include mass spectrometry, spectral analysis, electrochemical methods, chromatography, and so on^[15]. Due to the complexity of sample pretreatment, the diversity of environmental media, the slow analysis speed, and the low absolute content of pollutants, these methods are not only costly, but also cumbersome, making these detection methods face great challenges in environmental analysis, and some are not practical^[16-17]. Fluorescence detection has the characteristics of quantitative analysis, stable results, closed operation, high sensitivity, convenient operation, and safety. It is often selected in the detection work, and the selection of efficient and suitable fluorescent materials has attracted the attention of researchers^[18].

  Complexes are a class of organic-inorganic hybrid materials, which are functional porous crystalline materials with permanent intramolecular pore structures^[19-20]. It is constructed by metal ions or clusters and rigid organic ligands containing nitrogen and oxygen through coordination and self-assembly processes. Because of its adjustable pore structure, large specific surface area, and good stability, it is widely used in gas adsorption and separation, catalysis, biomedicine, photoelectric materials, energy storage, fluorescence sensing, and other fields. Due to the structural and performance characteristics of complex materials, in recent years, complexes and their composite materials have been used in the detection of many pollutants in the field of environmental pollution monitoring, and they have important application value in this field. Previous research has shown that complex materials have a wide range of applicability in radioactive substances, aromatic compounds, dyes, gases, heavy metals, and other fields^[21-23]. Transition metal ions with d¹⁰ electron configurations, such as Zn²⁺ and Cd²⁺, can promote radiation emission and are suitable for constructing luminescent complex materials^[24-25]. Introducing fluorescent substances into the metal centers, organic ligands, or pore structures of complexes can endow complexes with fluorescence sensing capabilities. Complex materials have many advantages, such as high stability, pre-concentration, and ratio fluorescence, and have been widely used in the analysis and detection of target substances, showing enormous potential in the field of fluorescence sensing. Based on this, we used the strategy of mixing nitrogen heterocyclic ligand dbim and carboxylic acid ligand (Fig.1) with cadmium nitrate tetrahydrate to construct a complex material by hydrothermal synthesis and generated a Cd(Ⅱ) complex {(H₂dbim)_0.5[Cd(Hbptc)]·H₂O}_n (1), where dbim=1-(4-((2, 6-dimethyl-2H-benzo[d]imidazol-3(3H)-yl)methyl)benzyl)-2, 7-dihydro-2, 5-dimethyl-1H-benzo[d]imidazole, H₄bptc=3, 3′, 4, 4′-benzophenone tetracarboxylic acid. The fluorescence intensity of complex 1 to solvent small molecules, antibiotics, phenols, and amines was detected. The experimental results show that complex 1 has an obvious quenching phenomenon for p- nitrophenol, tetracycline, and 2, 6-dichloro-4- nitroaniline, indicating that the quenched substances can be selectively identified.

  Figure 1

  

  Figure 1.  Structure of ligands dbim (a) and H₄bptc (b)

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  1.   Experimental

  1.1   General information and materials

  All reagents and solvents were commercially available, except for dbim, which was synthesized according to the literature^[26]. In the region of 400-4 000 cm^-1, FTIR spectra were recorded on an FTIR-7600 spectrophotometer. The content of C, H, and N was analyzed on a FLASH EA 1112 elemental analyzer. Powder X-ray diffraction (PXRD) patterns were conducted using Cu Kα₁ (λ=0.154 18 nm) radiation on a D8 Advance A25 diffractometer (working voltage: 40 kV, working current: 40 mA, scan range: 5°-90°). The fluorescence properties were studied using a Cary Eclipse fluorescence spectrophotometer.

  1.2   Synthesis of complex 1

  A mixture of Cd(NO₃)₂·4H₂O (0.2 mmol), dbim (0.1 mmol), H₄bptc (0.2 mmol), NaOH (0.2 mmol), and H₂O (9 mL) was placed in a 25 mL Teflon-lined stainless steel container. The mixture was sealed and heated at 150 ℃ for four days. After the mixture was cooled to ambient temperature at a rate of 5 ℃·h^-1, colorless crystals of 1 were obtained with a yield of 40% (based on Cd). Anal. Calcd. for C₃₀H₂₃CdN₂O₁₀(%): C, 52.68; H, 3.38; N, 4.09. Found(%): C, 52.70; H, 3.37; N, 4.11. IR (KBr, cm^-1): 3 458(m), 2 922(w), 1 664(s), 1 577(s), 1 382(m), 1 271(s), 1 242(w), 1 074(m), 850(s), 816(s), 748(s), 723(s).

  1.3   Crystal data collection and refinement

  The data of complex 1 was collected on an Xcalibur, Eos, Gemini CCD diffractometer (Mo Kα, λ=0.071 073 nm) at (20±1) ℃. Absorption correction was applied by using a multi-scan program. The data was corrected for Lorentz and polarization effects. The structure was solved by direct methods and refined with a full-matrix least-squares technique based on F ² with the SHELXL crystallographic software package/the SHELXL-97 crystallographic software package^[27]. Crystallographic crystal data and structure processing parameters for 1 are summarized in Table 1. Selected bond lengths and bond angles of 1 are listed in Table 2.

  Table 1

  

  Table 1.  Crystal data and structure refinement details for complex 1

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  Parameter	1		Parameter	1
  Formula	C30H23CdN2O10		γ / (°)	100.304(4)
  Formula weight	683.9		V / nm3	1.353 40(13)
  T / K	293(2)		Z	2
  Cryst system	Triclinic		Dc / (g·cm-3)	1.678
  Space group	P1		μ / mm-1	0.872
  a / nm	0.751 38(4)		F(000)	690
  b / nm	1.346 84(6)		2θ range / (°)	6.598-52.744
  c / nm	1.404 67(6)		GOF	1.025
  α / (°)	102.795(4)		R1 [I > 2σ(I)]a	0.045 8
  β / (°)	97.299(4)		wR2 [I > 2σ(I)]b	0.093 6
  ${ }^{\mathrm{a}} R_1=\sum\left\|F_{\mathrm{o}}|-| F_{\mathrm{c}}\right\| / \sum\left|F_{\mathrm{o}}\right| ;{ }^{\mathrm{b}} w R_2=\left[\sum w\left(F_{\mathrm{o}}^2-F_{\mathrm{c}}^2\right)^2 / \sum w\left(F_{\mathrm{o}}^2\right)^2\right]^{1 / 2} .$

  Table 2

  

  Table 2.  Selected bond lengths (nm) and bond angles (°) for complex 1

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  Cd1—O1	0.227 7(3)	Cd1—O2#2	0.225 0(2)	Cd1—O3#1	0.243 9(3)
  Cd1—O3	0.235 2(3)	Cd1—O4#1	0.238 8(3)	Cd1—O6#3	0.241 0(3)
  Cd1—O7#3	0.238 8(3)	Cd1#2—O2	0.225 0(2)	Cd1#1—O3	0.243 9(3)
  Cd1#1—O4	0.238 8(3)	Cd1#3—O6	0.241 0(3)	Cd1#3—O7	0.238 8(3)
  O1—Cd1—O3#1	82.76(10)	O1—Cd1—O3	81.51(10)	O1—Cd1—O4#1	131.38(10)
  O1—Cd1—O6#2	95.43(10)	O1—Cd1—O7#2	149.02(11)	O2#3—Cd1—O1	90.54(10)
  O2#3—Cd1—O3#1	107.87(9)	O2#3—Cd1—O3	171.51(10)	O2#3—Cd1—O4#1	84.36(11)
  O2#3—Cd1—O6#2	96.57(10)	O2#3—Cd1—O7#2	91.32(11)	O3—Cd1—O3#1	74.21(10)
  O3—Cd1—O4#1	103.11(11)	O3—Cd1—O6#2	81.33(10)	O3—Cd1—O7#2	93.98(11)
  O4#1—Cd1—O3#1	53.74(10)	O4#1—Cd1—O6#2	133.19(11)	O4#1—Cd1—O7#2	79.56(11)
  O6#2—Cd1—O3#1	155.49(10)	O7#2—Cd1—O3#1	125.69(11)	O7#2—Cd1—O6#2	53.64(11)
  Cd1—O3—Cd1#1	105.78(10)
  Symmetry codes: #1: 2-x, 1-y, 2-z; #2: 1-x, 1-y, 1-z; #3: 1-x, 1-y, 2-z.

  1.4   Fluorescence recognition test of complex 1

  Firstly, the fluorescence properties of complex 1 in different solvents were explored. The finely ground solid of 1 (1.5 mg) was added to a vial containing 3 mL of different solvents and then was sonicated for 15 min. After shaking the vial and pouring it into a cuvette, the fluorescence spectra of 1 were recorded.

  It is found through checking relevant information that all phenolic substances used in this experiment are soluble in ethanol. Therefore, ethanol was used as the solvent to prepare solutions of phenols. A pipette was used to take 3 mL of different phenol substances with a concentration of 1 mmol·L^-1, including o-aminophenol, 2, 4, 6-trichlorophenol, resorcinol, p-aminophenol, phenol, p-chlorophenol, 2, 4-dichlorophenol, p-nitrophenol, and placed in a sample bottle containing 1.5 mg complex 1. After ultrasonication for 15 min, the fluorescence test was started after standing for 5 min. The excitation wavelength was 280 nm and the slits were 5 and 20.

  After checking relevant information, it is found that ornidazole, sulfamethoxazole sodium, ceftriaxone sodium, and cefuroxime sodium are soluble in deionized water, while florfenicol, metronidazole, chloramphenicol, tetracycline, and erythromycin are soluble in ethanol. According to the above information, a certain concentration of solution was prepared with deionized water and ethanol as solvents. 3 mL of the above antibiotic solution with a concentration of 1 mmol·L^-1 was taken with a pipette and placed in a sample bottle containing 1.5 mg complex 1. After ultrasonication for 15 min, the solution was let to stand for 5 min and fluorescence detection began.

  The amine pollutants used in the experiment are all soluble in ethanol, so the solutions used are all prepared with ethanol. 3 mL of 1 mmol·L^-1 aniline, p-phenylenediamine, diphenylamine, diethylamine, 1-naphthylamine, and 2, 6-dichloro-4-nitroaniline (the same experimental steps as above) were measured. Then fluorescence detection was performed.

  2.   Results and discussion

  2.1   Crystal structure of complex 1

  Complex 1 crystallizes in the triclinic P1 space group. The Cd(Ⅱ) center displays a seven-coordinated geometry (Fig.2a), which is provided by seven oxygen atoms (O1, O2, O3, O4, O3A, O6, O7) from four Hbptc^3- anions with Cd—O bond distances in a range of 0.225 0(2)-0.243 9(3) nm. In 1, the dissociative H₂dbim adopts symmetric trans-conformation with a N_donor…N—C(sp³)…C(sp³) torsion angle of 150.291°. In 1, the Hbptc^3- anions connect four Cd(Ⅱ) cations, one carboxylate group takes μ₂-η¹∶η¹ coordination mode, the second carboxylate group adopts syn-anti-μ₂-η²∶η¹ fashion, the third shows μ₁-η¹∶η¹ coordination mode, while the forth doesn′t take part in coordination. Cd1 and Cd1#1 (Symmetry code: #1: 2-x, 1-y, 2-z) ions are held together by the carboxylate O atoms to form a binuclear unit [Cd₂(CO₂)₂].

  Figure 2

  

  Figure 2.  (a) Coordination environments of Cd(Ⅱ) in complex 1 with partial hydrogen atoms omitted for clarity (50% ellipsoid); (b) Schematic view of the 2D layer in 1

  Symmetry codes: #1: 2-x, 1-y, 2-z; #2: 1-x, 1-y, 1-z; #3: 1-x, 1-y, 2-z; #4: 1-x, -y, 1-z.

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  The Cd—Cd distance across the binuclear unit is 0.382 0 nm. The binuclear [Cd₂(CO₂)₂] units are connected by the Hbptc^3- ligands resulting in a 2D layer (Fig.2b). From a topological perspective, the dinuclear unit [Cd₂(CO₂)₂] acts as a four connected node, and complex 1 represents {4⁴·6⁶} topology by using Hbptc^3- ligands as linkers (Fig.2c).

  2.2   PXRD analysis of complex 1

  PXRD analysis was performed to check the purity of complex 1 (Fig.3). The peak positions of the as- synthesized sample were aligned with those simulated.

  Figure 3

  

  Figure 3.  Experimental and simulated PXRD patterns of complex 1

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  2.3   Fluorescence recognition test of complex 1

  2.3.1   Fluorescence recognition to solvents

  Fig.4 shows that complex 1 has fluorescence quenching in acetone, xylene, and cyclohexanone, and fluorescence enhancement in ethanol, cyclohexane, toluene, and isopropanol. However, most organic pollutants are easily soluble in ethanol, which can be used as a solvent, and the fluorescence intensity in deionized water is also strong, so deionized water can also be used as the solvent of these pollutants.

  Figure 4

  

  Figure 4.  Fluorescence intensity of complex 1 in different solvents

  1: cyclohexane; 2: toluene; 3: isopropanol; 4: ethanol; 5: dioxane; 6: THF; 7: n-hexane; 8: dichloromethane; 9: distilled water; 10: ethyl acetate; 11: methanol; 12: acetonitrile; 13: DMF; 14: ethylene glycol; 15: chloroform; 16: dimethyl sulfoxide; 17: acetone; 18: cyclohexanone; 19: xylene

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  2.3.2   Fluorescence recognition of phenols

  The test results are shown in Fig.5. Complex 1 shows different fluorescence quenching ratios in the presence of different phenolic substances. Its fluorescence intensities were reduced in the presence of o-aminophenol, p-aminophenol, 2, 4, 6- trichlorophenol, p-nitrophenol, 2, 4-dichlorophenol, phenol, p-chlorophenol, and resorcinol, but the fluorescence quenching for p-nitrophenol is the most obvious. Therefore, complex 1 can be used as a fluorescent probe to detect p-nitrophenol in the environment.

  Figure 5

  

  Figure 5.  Fluorescence intensities of complex 1 in various phenol alcohol solutions

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  To further explore the sensitivity of complex 1 to p-nitrophenol, 0.1 mol·L^-1 p-nitrophenol was gradually added to the sample. As shown in Fig.6. With the increase in the volume of p-nitrophenol, the fluorescence intensity decreased significantly. When the volume of p-nitrophenol solution reached 525.9 μL, the fluorescence intensity was almost quenched, indicating that complex 1 could selectively recognize p-nitrophenol.

  Figure 6

  

  Figure 6.  Fluorescence spectra of complex 1 dispersed in alcohol upon the addition of p-nitrophenol (0.1 mol•L^-1)

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  The quenching equation can be written as I₀/I=1.072 7+2×10²c_a, where I₀ and I are fluorescence intensities before and after the addition of the analyte, respectively, and c_a is the concentration of the analyte (Fig.7). The quenching constant was 2×10² L·mol^-1. The limit of detection (LOD) was 3.18×10^-2 mol·L^-1.

  Figure 7

  

  Figure 7.  Linear correlation graph for the plot of I₀/I vs concentration of p-nitrophenol

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  2.3.3   Fluorescence recognition of antibiotics

  From Fig.8 and 9, it can be seen that sulfamethoxazole sodium, ornidazole, ceftiofur sodium, cefuroxime sodium, metronidazole, chloramphenicol, erythromycin, and tetracycline have fluorescence quenching effect on complex 1, and florfenicol has a small amount of fluorescence enhancement. Since tetracycline has the strongest fluorescence quenching effect on 1, we further studied the sensitivity of 1 to tetracycline. 0.1 mol·L^-1 tetracycline was added to the sample dissolved in ethanol step by step for fluorescence detection (Fig.10). When the volume of tetracycline solution reached 5.6 μL, the fluorescence intensity was extremely low, indicating that complex 1 can better identify tetracycline. The quenching equation can be written as I₀/I=0.393 1+5.4×10⁴c_a (Fig.11). The quenching constant was 5.4×10⁴ L·mol^-1. The LOD was 1.17×10^-4 mol·L^-1.

  Figure 8

  

  Figure 8.  Fluorescence intensities of complex 1 in various antibiotic alcohol solutions

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  Figure 9

  

  Figure 9.  Fluorescence intensities of complex 1 in various antibiotic aqueous solutions

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  Figure 10

  

  Figure 10.  Fluorescence spectra of complex 1 dispersed in alcohol upon the addition of tetracycline (0.1 mol•L^-1)

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  Figure 11

  

  Figure 11.  Linear correlation graph for the plot of I₀/I vs concentration of tetracycline

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  2.3.4   Fluorescence recognition of amines

  The experimental results are shown in Fig.12. It can be seen that the fluorescence intensities of complex 1 in the presence of various amines decreased, but the fluorescence quenching effect of 2, 6-dichloro-4-nitroaniline on complex 1 was the strongest.

  Figure 12

  

  Figure 12.  Fluorescence intensities of complex 1 in various amine alcohol solutions

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  To further study the recognition of this amine, 0.1 mol·L^-1 2, 6-dichloro-4-aniline was added into the alcohol solution of complex 1 step by step. The experimental results are shown in Fig.13. When the volume of 2, 6-dichloro-4-aniline was increased to 17.5 μL, the fluorescence intensity was almost zero. So, complex 1 can selectively recognize 2, 6-dichloro-4-aniline. The quenching equation can be written as I₀/I=0.949 7+2×10⁴c_a (Fig.14). The quenching constant was 2×10⁴ L·mol^-1. The LOD was 3.18×10^-4 mol·L^-1.

  Figure 13

  

  Figure 13.  Fluorescence spectra of complex 1 dispersed in alcohol upon the addition of 2, 6-dichloro-4-nitroaniline (0.1 mol•L^-1)

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  Figure 14

  

  Figure 14.  Linear correlation graph for the plot of I₀/I vs concentration of 2, 6-dichloro-4-nitroaniline

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  3.   Conclusions

  A new Cd(Ⅱ) complex 1 was prepared using the hydrothermal method in this study. It was found that 1 has strong selectivities for p-nitrophenol, tetracycline, and 2, 6-dichloro-4-nitroaniline because of their strong fluorescence quenching effects on 1. Complex 1 can be utilized for the selective recognition of these pollutants, providing a novel detection material for environmental contamination detection.

  
  
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  Figure 1  Structure of ligands dbim (a) and H₄bptc (b)

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  Figure 2  (a) Coordination environments of Cd(Ⅱ) in complex 1 with partial hydrogen atoms omitted for clarity (50% ellipsoid); (b) Schematic view of the 2D layer in 1

  Symmetry codes: #1: 2-x, 1-y, 2-z; #2: 1-x, 1-y, 1-z; #3: 1-x, 1-y, 2-z; #4: 1-x, -y, 1-z.

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  Figure 3  Experimental and simulated PXRD patterns of complex 1

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  Figure 4  Fluorescence intensity of complex 1 in different solvents

  1: cyclohexane; 2: toluene; 3: isopropanol; 4: ethanol; 5: dioxane; 6: THF; 7: n-hexane; 8: dichloromethane; 9: distilled water; 10: ethyl acetate; 11: methanol; 12: acetonitrile; 13: DMF; 14: ethylene glycol; 15: chloroform; 16: dimethyl sulfoxide; 17: acetone; 18: cyclohexanone; 19: xylene

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  Figure 5  Fluorescence intensities of complex 1 in various phenol alcohol solutions

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  Figure 6  Fluorescence spectra of complex 1 dispersed in alcohol upon the addition of p-nitrophenol (0.1 mol•L^-1)

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  Figure 7  Linear correlation graph for the plot of I₀/I vs concentration of p-nitrophenol

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  Figure 8  Fluorescence intensities of complex 1 in various antibiotic alcohol solutions

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  Figure 9  Fluorescence intensities of complex 1 in various antibiotic aqueous solutions

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  Figure 10  Fluorescence spectra of complex 1 dispersed in alcohol upon the addition of tetracycline (0.1 mol•L^-1)

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  Figure 11  Linear correlation graph for the plot of I₀/I vs concentration of tetracycline

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  Figure 12  Fluorescence intensities of complex 1 in various amine alcohol solutions

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  Figure 13  Fluorescence spectra of complex 1 dispersed in alcohol upon the addition of 2, 6-dichloro-4-nitroaniline (0.1 mol•L^-1)

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  Figure 14  Linear correlation graph for the plot of I₀/I vs concentration of 2, 6-dichloro-4-nitroaniline

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  Table 1.  Crystal data and structure refinement details for complex 1

  Parameter	1		Parameter	1
  Formula	C30H23CdN2O10		γ / (°)	100.304(4)
  Formula weight	683.9		V / nm3	1.353 40(13)
  T / K	293(2)		Z	2
  Cryst system	Triclinic		Dc / (g·cm-3)	1.678
  Space group	P1		μ / mm-1	0.872
  a / nm	0.751 38(4)		F(000)	690
  b / nm	1.346 84(6)		2θ range / (°)	6.598-52.744
  c / nm	1.404 67(6)		GOF	1.025
  α / (°)	102.795(4)		R1 [I > 2σ(I)]a	0.045 8
  β / (°)	97.299(4)		wR2 [I > 2σ(I)]b	0.093 6
  ${ }^{\mathrm{a}} R_1=\sum\left\|F_{\mathrm{o}}|-| F_{\mathrm{c}}\right\| / \sum\left|F_{\mathrm{o}}\right| ;{ }^{\mathrm{b}} w R_2=\left[\sum w\left(F_{\mathrm{o}}^2-F_{\mathrm{c}}^2\right)^2 / \sum w\left(F_{\mathrm{o}}^2\right)^2\right]^{1 / 2} .$

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  Table 2.  Selected bond lengths (nm) and bond angles (°) for complex 1

  Cd1—O1	0.227 7(3)	Cd1—O2#2	0.225 0(2)	Cd1—O3#1	0.243 9(3)
  Cd1—O3	0.235 2(3)	Cd1—O4#1	0.238 8(3)	Cd1—O6#3	0.241 0(3)
  Cd1—O7#3	0.238 8(3)	Cd1#2—O2	0.225 0(2)	Cd1#1—O3	0.243 9(3)
  Cd1#1—O4	0.238 8(3)	Cd1#3—O6	0.241 0(3)	Cd1#3—O7	0.238 8(3)
  O1—Cd1—O3#1	82.76(10)	O1—Cd1—O3	81.51(10)	O1—Cd1—O4#1	131.38(10)
  O1—Cd1—O6#2	95.43(10)	O1—Cd1—O7#2	149.02(11)	O2#3—Cd1—O1	90.54(10)
  O2#3—Cd1—O3#1	107.87(9)	O2#3—Cd1—O3	171.51(10)	O2#3—Cd1—O4#1	84.36(11)
  O2#3—Cd1—O6#2	96.57(10)	O2#3—Cd1—O7#2	91.32(11)	O3—Cd1—O3#1	74.21(10)
  O3—Cd1—O4#1	103.11(11)	O3—Cd1—O6#2	81.33(10)	O3—Cd1—O7#2	93.98(11)
  O4#1—Cd1—O3#1	53.74(10)	O4#1—Cd1—O6#2	133.19(11)	O4#1—Cd1—O7#2	79.56(11)
  O6#2—Cd1—O3#1	155.49(10)	O7#2—Cd1—O3#1	125.69(11)	O7#2—Cd1—O6#2	53.64(11)
  Cd1—O3—Cd1#1	105.78(10)
  Symmetry codes: #1: 2-x, 1-y, 2-z; #2: 1-x, 1-y, 1-z; #3: 1-x, 1-y, 2-z.

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