Synthesis,crystal structure and bovine serum albumin–binding studies of a new Cd(II) complex incorporating 2,2′-(propane-1,3-diyl)bis(1H-imidazole-4,5-dicarboxylate)

Abstract

A new Cd(II) complex, [Cd(H₄pbidc)(H₂O)]_n (1), incorporating 2,2′-(propane-1,3-diyl)bis(1H- imidazole-4,5-dicarboxylic acid) (H₆pbidc) was synthesized and characterized by elemental analysis, infrared spectra and X-ray single-crystal diffraction. In complex 1, each Cd(II) ion is hepta-coordinated, showing a significantly distorted pentagonal-bipyramidal coordination environment. Adjacent Cd(II) ions are alternately joined through two carboxylate oxygen atoms and two bridging water molecules resulting in a one-dimensional chain structure. In the solid state, adjacent chains are further linked by hydrogen bonds, forming a three-dimensional supramolecular architecture. Meanwhile, the interactions of complex 1 with bovine serum albumin were analysed by fluorescence measurements under physiological conditions. The results indicated that the fluorescence intensity of bovine serum albumin was decreased considerably upon the addition of complex 1 through a static quenching mechanism with formation of one binding site. The negative values of the thermodynamic parameters including enthalpy change (ΔH), entropy change (ΔS) and Gibbs free energy change (ΔG) showed that hydrogen bonding and van der Waals forces were the main interactions in the binding of complex 1 to bovine serum albumin, and the binding process is spontaneous in thermodynamics.

Keywords

Cd(II) complex crystal structure fluorescence quenching interaction with bovine serum albumin thermodynamic parameter

Graphical abstract synopsis

A new one-dimensional Cd(II) complex, [Cd(H₄pbidc)(H₂O)]_n (1), base on 2,2′-(propane-1,3-diyl)bis(1H-imidazole-4,5-dicarboxylic acid) (H₆pbidc) has been synthesized and characterized by single-crystal X-ray diffraction. In addition, the interactions of complex 1 with bovine serum albumin were also analysed by fluorescence measurements under physiological conditions.

Introduction

Rational design and synthesis of metal-organic complexes (discrete or polymeric) have attracted considerable interest owing to their structural diversity and significant potential applications in catalysis, ion exchange, chemical sensing and drug delivery.^1–6 Although many factors need to be considered in the construction of the complexes, careful choice of the organic ligands has been paid more attention in crystal engineering than ever.^7–10 It is well known that imidazole and its derivatives, such as imidazole-4,5-dicarboxylic acid, 2-(hydroxymethyl)-1H-imidazole-4,5-dicarboxylic acid, 2-phenyl-1H-imidazole-4,5-dicarboxylic acid, 2-(pyridin-4-yl)-1H-imidazole-4,5-dicarboxylic acid, 2,2′-(1,2-phenylene)bis(1H-imidazole-4,5-dicarboxylic acid), 2,2′-(ethane-1,2-diyl)bis(1H-imidazole-4,5-dicarboxylic acid), are widely used in the preparation of new coordination complexes since they contain N-atom donors, as well as O-atom donors, and have a rich variety of coordination modes which can lead to complexes with intriguing structures and interesting properties.^11–17 Among the reported ligands, 2,2′-(propane-1,3-diyl)bis(1H-imidazole-4,5-dicarboxylic acid) (H₆pbidc) is a good linker since it has 12 potential donors and can coordinate to almost all soft and hard metal ions with various coordination modes, resulting in final products with diverse structures. To the best of our knowledge, only four mononuclear complexes based on H₆pbidc ligand have been reported.^18–21 In order to further enrich the categories and numbers of complexes based on this ligand, we continue the use of H₆pbidc as a ligand to self-assemble with CdCl₂·2.5H₂O and have successfully obtained a new one-dimensional (1D) complex [Cd(H₄pbidc)(H₂O)]_n. In addition to the determination of the single-crystal structure of complex 1, its interaction with bovine serum albumin (BSA) was also investigated.

Experimental

General information and materials

BSA was purchased from Aokxing biotechnology Co, Ltd, Beijing, and was used without further purification. Tris and dimethyl sulfoxide (DMSO) were obtained from Sinopsin group chemical reagent Co, Ltd. Other chemicals were of analytical reagent grade and were used without further purification. Double-distilled water was used throughout the experiment. The element analyses (C, H and N) were obtained by a FLASH EA 1112 elemental analyzer (Thermo Fisher Scientific Company, Waltham, MA, USA). The infrared (IR) data were recorded on a Nicolet iS50 spectrophotometer (Thermo Scientific, Waltham, MA, USA) with KBr pellets in the range 400–4000 cm⁻¹. All fluorescence measurements were carried out on an F-7000 spectrofluorimeter (Hitachi, Ltd., Chiyoda-ku, Tokyo, Japan) equipped with a thermostat bath and 1.0-cm quartz cells. Fluorescence quenching spectra of BSA were recorded from 285 to 450 nm at an excitation wavelength of 280 nm. The width of the excitation and emission slit was set to 5.0 and 5.0 nm, respectively. All quenching experiments were performed at 298, 308 and 313 K, for BSA concentration of 1.0 × 10⁻⁶ mol L⁻¹, and for complex 1 of 0–5.9 × 10⁻⁴ mol L⁻¹.

Synthesis of [Cd(H₄pbidc)(H₂O)]_n (1)

A mixture of CdCl₂·2.5H₂O (0.05 mmol), H₆pbidc (0.05 mmol), methanol (2 mL) and distilled water (4 mL) was sealed in a 25-mL Teflonlined stainless steel container and heated at 413 K for 72 h. After the mixture had been allowed to cool to room temperature at a rate of 5 K h⁻¹, colourless crystals of [Cd(H₄pbidc)(H₂O)]_n (1) suitable for X-ray analysis were obtained (yield 63%, based on Cd; Scheme 1). Calcd. for C₁₃H₁₂CdN₄O₉: C, 32.48; H, 2.52; N, 11.66%. Found: C, 32.01; H, 2.45; N, 11.86%. IR (KBr, cm⁻¹): 3278 (s), 2950 (w), 2923 (w), 1724 (s), 1585 (s), 1531 (s), 1490 (s), 1434 (s), 1392 (s), 1272 (s), 1125 (w), 972 (w), 848 (w), 782 (s), 719 (m), 514 (w).

Scheme 1.

The reaction for the synthesis of complex 1.

Preparation of stock solutions

BSA (relative molecular weight 65,000) was dissolved in Tris-HCl buffer (pH = 7.36, containing 0.1 mol L⁻¹ Tris, 0.1 mol L⁻¹ NaCl) to prepare a stock solution of 5.00 × 10⁻⁵ mol L⁻¹ and was kept refrigerated at 273—277 K. A sample of 5.00 × 10⁻³ mol L^–1 stock solution of complex 1 was obtained by dissolving it in DMSO and which were kept in the dark at 273–277 K. Working solutions were prepared daily by diluting these stock solutions with the same buffer.

Single-crystal structure determination

Single-crystal X-ray diffraction data collection for complex 1 was carried out at room temperature on a D8 VENTURE diffractometer (Bruker AXS GmbH, Karlsruhe, Germany) with Mo Kα radiation (λ = 0.71073 Å). The data were corrected for Lorentz and polarization effects. The structure was solved by direct methods using the SHELXS programme of the SHELXT package and refined by full-matrix least-squares methods based on F² with the SHELXL crystallographic software package.^22,23 All non-hydrogen atoms were refined anisotropically. Hydrogens bond to carbon and nitrogen were positioned geometrically and refined using a riding model. Hydrogens of water molecules were found at reasonable positions in the differential Fourier map and located there. All hydrogens were included in the final refinement. Crystallographic parameters and structural refinement for complex 1 are summarized in Table 1. Selected bond lengths and bond angles are listed in Table 2. Hydrogen bonds are listed in Table 3. Crystallographic data for the structural analysis have been deposited with the Cambridge Crystallographic Data Centre (CCDC No. 1945816). Copies of this information may be obtained free of charge from the Director, CCDC, 12 Union Road, Cambridge, CBZ 1EZ, UK (Fax: +44-1223-336033; email: deposit@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk).

Table 1.

Crystal data and structure refinement for complex 1.

Empirical formula	C₁₃H₁₂CdN₄O₉
Formula weight	480.67
Temperature (K)	293(2) K
Crystal system	Triclinic
Space group	P-1
Unit cell dimensions (Å, deg)
a/Å	7.0034(2)
b/Å	9.9105(3)
c/Å	10.7217(4)
α/deg	79.3750(10)
β/deg	87.4410(10)
γ/deg	88.9070(10)
V/Å³	730.63(4)
Z	2
D_calc (g cm⁻³)	2.185
μ (mm⁻¹)	1.562
F(000)	476
Reflections collected/unique	27796/3388 (R(int) = 0.0263)
Data/restraints/parameters	3388/0/245
Goodness-of-fit on F²	1.112
Final R indices (I>2σ(I))	R₁ = 0.0158, wR₂ = 0.0411
R indices (all data)	R₁ = 0.0173, wR₂ = 0.0418

Table 2.

Selected bond lengths (Å) and angles (^o) for complex 1.

Cd(1)–N(1)	2.2781(13)	Cd(1)–N(3)	2.2902(12)
Cd(1)–O(9)	2.2992(11)	Cd(1)–O(8)#1	2.3758(11)
Cd(1)–O(1)	2.4328(12)	Cd(1)–O(8)	2.4997(11)
Cd(1)–O(9)#2	2.6023(11)
N(1)–Cd(1)–N(3)	93.36(5)	N(1)–Cd(1)–O(9)	142.84(4)
N(3)–Cd(1)–O(9)	114.58(4)	N(1)–Cd(1)–O(8)#1	90.02(4)
N(3)–Cd(1)–O(8)#1	120.86(4)	O(9)–Cd(1)–O(8)#1	95.38(4)
N(1)–Cd(1)–O(1)	71.68(4)	N(3)–Cd(1)–O(1)	151.26(5)
O(9)–Cd(1)–O(1)	72.31(4)	O(8)#1–Cd(1)–O(1)	84.46(4)
N(1)–Cd(1)–O(8)	137.14(4)	N(3)–Cd(1)–O(8)	68.72(4)
O(9)–Cd(1)–O(8)	78.27(4)	O(8)#1–Cd(1)–O(8)	69.49(4)
O(1)–Cd(1)–O(8)	138.36(4)	N(1)–Cd(1)–O(9)#2	89.21(4)
N(3)–Cd(1)–O(9)#2	81.17(4)	O(9)–Cd(1)–O(9)#2	72.55(4)
O(8)#1–Cd(1)–O(9)#2	157.96(4)	O(1)–Cd(1)–O(9)#2	74.40(4)
O(8)–Cd(1)–O(9)#2	123.59(4)

Symmetry transformations used to generate equivalent atoms: #1 −x + 1, −y + 1, −z + 1; #2 −x, −y + 1, −z + 1.

Table 3.

Hydrogen bonds for complex 1.

D–H···A	d(D–H) (Å)	d(H···A) (Å)	d(D···A) (Å)	(D–H···A) (°)
O(2)–H(2)···O(3)	0.82	1.63	2.4528(19)	177.1
O(3)–H(3)···O(2)	0.82	1.63	2.4528(19)	177.5
O(6)–H(6)···O(7)	0.82	1.68	2.4977(17)	174.7
N(2)–H(2A)···O(7)#3	0.86	2.20	3.0506(18)	171.2
N(4)–H(4)···O(2)#4	0.86	2.41	3.1419(19)	143.8
O(9)–H(9A)···O(5)#5	0.85	1.86	2.7042(16)	170.5
O(9)–H(9B)···O(4)#6	0.85	1.79	2.6348(17)	176.2

Symmetry transformations used to generate equivalent atoms: #3 x, y, z − 1; #4 x, y + 1, z; #5 x, y − 1, z; #6 x, y, z + 1.

Results and discussion

Crystal structure of [Cd(H₄pbidc)(H₂O)]_n (1)

The asymmetric unit of complex 1 comprises one Cd(II) cation, one H₄pbidc²⁻ dianion and one coordinated water molecule. As shown in Figure 1, each Cd(II) ion is hepta-coordinated, showing a significantly distorted pentagonal-bipyramidal coordination environment. The equatorial plane is defined by two nitrogen atoms (N1 and N3) and two oxygen atoms (O1 and O8) from an H₄pbidc²⁻ ligand and one coordinated water molecule (O9). The axial positions are occupied by O8#1 from another H₄pbidc²⁻ ligand and O9#2 from another coordinated water molecule with the bond angle of O8#1–Cd1–O9#2 being 157.96(4)° (symmetry code: #1 −x + 1, −y + 1, −z + 1; #2 −x, −y + 1, −z + 1). The two imidazole rings are not co-planar, with a dihedral angle between the two least-square planes N1/N2/C2/C3/C5 and N3/N4/C9/C11/C12 of 44.25(5)°. The dihedral angles between the mean planes defined the imidazole ring N1/N2/C2/C3/C5 and the coordinated and uncoordinated carboxylate groups are 2.0(2)° and 1.57(17)°, respectively, while the dihedral angles between the mean planes defined the imidazole ring N3/N4/C9/C11/C12 and the coordinated and uncoordinated carboxylate groups are 9.4(2)° and 1.61(18)°, respectively. The Cd–N bond lengths are 2.2781(13) and 2.2902(12) Å, while the Cd–O bond distances are in the range of 2.2992(11)–2.6023(11) Å, all of which are in the normal range of those observed in the reported Cd(II) complexes {[Cd(glu)(imb)]·H₂O}_n [imb = 2-(1H-imidazolyl-1-methyl)-1H-benzimidazole, H₂glu = glutaric acid, Cd–N = 2.236(2)–2.325(2) Å, Cd–O = 2.212(2)–2.644(2) Å]²⁴ and [Cd₂(cbimdaH)₂(H₂O)₆]_n·(DMF)_3n·(H₂O)_3n [cbimdaH₃ = 1-(4-carboxybenzyl)-1H-imidazole-4,5-dicarboxylic acid, Cd–N = 2.263(3)–2.294(3) Å, Cd–O = 2.252(4)–2.673(3) Å].²⁵

Figure 1.

Coordination environment of the Cd(II) ion in complex 1 with the atom numbering scheme, displacement ellipsoids are drawn at the 30% probability level.

As depicted in Figure 2, as well as two imidazole nitrogen atoms and two carboxylato oxygen atoms of the same H₄pbidc²⁻ ligand chelate to one Cd(II) ion, the O8 atom also bridges the neighbouring Cd(II) ion. Similarly, the coordinated water molecule O9 also links two neighbouring Cd(II) ions. So the adjacent Cd(II) ions are alternately joined through two carboxylate oxygen atoms (Cd1–Cd1#1: 4.0067(1) Å) and two bridging water molecules (Cd1–Cd1#2: 3.9556(1) Å) to form a 1D chain structure running along the crystallographic a axis. Intramolecular O–H···O hydrogen bonds between the carboxyl and carboxylate groups stabilizes the 1D chain. As shown in Figure 3 and Table 3, there are O9–H9B···O4 hydrogen bonds between the coordinated water molecules and carboxylate groups, and N2–H2A···O7 hydrogen bonds between the imidazole groups and carboxylate groups. Therefore, adjacent 1D chains are connected through the above two kinds of hydrogen bonds, leading to an infinite two-dimensional layered structure parallel to the ac plane. Adjacent layers are further linked by O9–H9A···O5 hydrogen bonds between the coordinated water molecules and carboxylate groups, and N4–H4···O2 hydrogen bonds between the imidazole groups and carboxylate groups, forming a three-dimensional supramolecular architecture in the solid state (Figure 4).

Figure 2.

A view of the one-dimensional structure of complex 1.

Figure 3.

The two-dimensional structure of complex 1 linked by hydrogen bonds (dashed lines).

Figure 4.

The three-dimensional structure of complex 1 linked by hydrogen bonds (dashed lines).

Through investigation of the literature, we found that four complexes involving H₆pbidc ligand, including [Mn(H₄pbidc)(H₂O)₂],¹⁸ [Ni(H₄pbidc)(H₂O)₂]·2H₂O,¹⁹ [Ca(H₄pbidc)(H₂O)₃]·4H₂O²⁰, and [Co(H₄pbidc)(pyridine)]·4,4′-bipyridine,²¹ have been reported. In this work, a new complex [Cd(H₄pbidc)(H₂O)]_n (1) with different compositions and architectures from those of the reported complexes can be obtained by using CdCl₂·2.5H₂O and H₆pbidc as starting materials. As shown in Scheme 2, H₄pbidc²⁻ anion only coordinates to one metal ion in N,O-chelating fashion (Scheme 2, mode (a)) in the reported complexes, but the H₄pbidc²⁻ anion coordinates to two Cd(II) ions with coordination mode (b), which is unprecedented. Furthermore, the coordination modes of the water molecules in complex 1 are different from those in the reported complexes. Water molecules coordinate to metal ions in monodentate mode in the reported complexes, while water molecules coordinate to two Cd(II) ions in bridging mode in complex 1. As a result, all of the four reported complexes exhibit mononuclear structure, complex 1 displays 1D structure. These results indicate that H₄pbidc²⁻ is a good ligand and that the nature of the ligand plays significant roles in dominating molecular self-assembled structure.

Scheme 2.

Coordination modes of H₄pbidc²⁻ anion found in the reported M-H₆pbidc complexes (a) and the new coordination mode in complex 1 (b).

Fluorescence quenching spectra and quenching mechanism

Fluorescence measurements were carried out to investigate whether complex 1 bounds to BSA.

The effects of complex 1 on BSA were evaluated by measuring the intrinsic florescence intensity of the BSA before and after addition of complex 1. Figure 5 shows the fluorescence emission spectra of BSA in the absence and presence of complex 1. Obviously, BSA had a strong fluorescence emission band at 340 nm by fixing the excitation wavelength at 280 nm. Under the same conditions, no fluorescence of complex 1 was observed. It can be observed that the fluorescence intensity of BSA decreases regularly with the increase addition of complex 1, but there is no significant emission wavelength shift. The strong quenching of BSA fluorescence clearly indicated that the interaction between complex 1 and BSA took place and resulted in quenching the intrinsic fluorescence of BAS.²⁶

Figure 5.

The quenching effect of complex 1 on BSA fluorescence at 298 K (a), 308 K (b) and 313 K (c).

Quenching can be classified as either dynamic or static quenching by different mechanisms. Dynamic quenching results from collision between fluorophore and quencher, and static quenching is due to the formation of ground-state complex between fluorophore and quencher. The quenching mechanism of the drugs with BSA was probed using the Stern–Volmer equation²⁶

\frac{F_{0}}{F} = 1 + K_{q} τ_{0} [Q] = 1 + K_{s v} [Q]

(1)

where F₀ and F are the fluorescence intensity of BSA in the absence and presence of quenching agent (complex 1), respectively, K_q is the quenching rate constant of the biomolecule, K_sv is the Stern–Volmer quenching constant, τ₀ is the average lifetime of the molecule without quencher, and [Q] is the concentration of the quenching agent (complex). Hence, equation (1) was applied to determine K_sv by linear regression from a plot of F₀/F against [Q]. Dynamic and static quenching can be distinguished by the quenching constant K_q. According to the literature for dynamic quenching, the maximum scatter collision quenching constant of various quenchers with the biopolymer is 2.0 × 10¹⁰ L mol⁻¹ s⁻¹.²⁶ For the drug-BSA systems, the Stern–Volmer graphs are presented in Figure 6, and the values of K_sv and K_q (= K_sv/τ₀, τ₀ = 10⁻⁸ s)²⁷ obtained from the plots at 298, 308 and 313 K are shown in Table 4. The values of K_q are larger than 2.0 × 10¹⁰ L mol⁻¹ s⁻¹, which suggest that the fluorescence quenching is caused by a specific interaction between BSA and complex 1, and the quenching mechanism mainly arise from complexes formation, while dynamic collision could be negligible in the concentration range studied.²⁶

Figure 6.

The Stern–Volmer curves for quenching of complex 1 with BSA at 298, 308 and 313 K, Q is the concentrations of complex 1.

Table 4.

The quenching constants between complex 1 and BSA.

T/K	K_q (L mol⁻¹ s⁻¹)	K_sv (L mol⁻¹)
298	5.60 × 10¹¹	5.60 × 10³
308	6.11 × 10¹¹	6.11 × 10³
313	7.22 × 10¹¹	7.22 × 10³

Binding parameter and binding mode

For static quenching, the relationship between fluorescence quenching intensity and the concentration of quenchers can be described by the modified form of the Stern–Volmer equation²⁸

Log [\frac{F_{0} - F}{F}] = Log K_{b} + n Log [Q]

(2)

where K_b is the binding constant and n is the number of binding sites.

Plots of Log((F₀ − F)/F) versus log[Q] yields logK_b as the intercept and n as the slope (see Figure 7). As can be seen from Table 5, the binding constants K_b decreased with the increasing of temperature, which may indicate forming an unstable compound. The unstable compound would be partly decomposed with the rising temperature; therefore, the values of K_b decreased. The values of n at the experimental temperatures were approximately equal to 1, which indicated the existence of a single binding site in BSA for complex 1. The decrease in the values of n may be attributed to the fact that the capacity of the complex binding to BSA is decreased when increasing the temperature.

Figure 7.

Double-log plots of complex 1 quenching effects on BSA fluorescence at 298, 308 and 313 K.

Table 5.

The thermodynamic parameters for the binding of complex 1 to BSA.

T/K	K_b (L mol⁻¹ s⁻¹)	n	ΔH (kJ/mol)	ΔS (J/mol K)	ΔG (kJ/mol)
298	3.23 × 10⁵	1.46	–180.00	–498.56	–31.43
308	1.68 × 10⁴	1.11		–503.54	–24.91
313	7.84 × 10³	1.00		–500.54	–23.33

Essentially, there are four types of non-covalent interactions that could play a key role in drug binding to proteins including hydrogen bonds, van der Waals forces, electrostatic and hydrophobic interactions.²⁹ The thermodynamic parameters, enthalpy change (ΔH) and entropy change (ΔS) for the binding reaction are the main evidence to confirm binding modes. From the thermodynamic standpoint, ΔH > 0 and ΔS > 0 imply a hydrophobic interaction; ΔH < 0 and ΔS < 0 reflect the van der Waals forces and hydrogen bond interactions; and ΔH ≈ 0 and ΔS > 0 suggest an electrostatic force.²⁶ In order to elucidate the binding mode, the binding constant of complex 1 to BSA was evaluated at three different temperatures. Since the temperature effect was very small in the studied range of temperature, the interaction enthalpy change can be regarded as a constant. Therefore, the enthalpy change (ΔH), Gibbs free energy change (ΔG) and entropy change (ΔS) for the binding processes can be calculated by equations (3)–(5)

Ln (\frac{K_{b 2}}{K_{b 1}}) = Δ H \frac{(1 / T_{1} - 1 / T_{2})}{R}

(3)

Δ G = - R T Ln K_{b}

(4)

Δ S = \frac{Δ H - Δ G}{T}

(5)

where K_b is the binding constant at the corresponding temperature, and R is the gas constant.

As shown in Table 5, the enthalpy change (ΔH) and entropy change (ΔS) of the combination processes at different temperatures are all negative, which indicated that these bindings are an exdothermic and entropy decreasing processes. The negative value for Gibbs free energy (ΔG) suggests that the binding process for the interaction between complex 1 and BSA is spontaneous in thermodynamics. Moreover, the binding process investigated in the current work is predominantly due to hydrogen bonding and van der Waals forces.³⁰

The interactions between BSA and the free ligand H₆pbidc or free CdCl₂ have also been investigated under the same experimental conditions. As shown in Supplemental Figures S1 and S2 (see supporting information), the fluorescence intensity of BSA was little changed with the increase addition of the free ligand H₆pbidc or free CdCl₂. Furthermore, we have determined the molecular weight of the complex 1 in DMSO solution. The results show that the number average molecular weight is 4124. Thus, we confirm that the skeleton of the complex 1 is intact in DMSO solution. So to some extent, the properties of complex 1 in solution can represent the properties of the crystals.³¹

Conclusion

Through the solvothermal reaction of CdCl₂·2.5H₂O with H₆pbidc, a new complex, [Cd(H₄pbidc)(H₂O)]_n (1), has been obtained. It displays a 1D structure in which Cd(II) ions are connected alternately by bridging carboxylate oxygen atoms and bridging water molecules. The structure and the coordination mode of the H₄pbidc²⁻ anion are different from the reported complexes based on H₆pbidc ligand. For example, [Ca(H₄pbidc)(H₂O)₃]·4H₂O, [Ni(H₄pbidc)(H₂O)₂]·2H₂O and [Mn(H₄pbidc)(H₂O)₂] are mononuclear complexes in which each tetradentate H₄pbidc²⁻ anion only coordinate to one metal ion in N,O-chelating fashion.^18–20 These results indicate that changing the metal ion can influence the coordination mode of H₄pbidc²⁻ anion and thus influence the structures and properties of the resulting complexes. The BSA-binding properties of complex 1 were investigated by fluorescence measurements. The experimental results showed that complex 1 has good BSA-binding abilities, and the binding reactions between complex 1 and BSA were mainly hydrogen bonding and van der Waals forces.

Supplemental Material

Supporting_Information – Supplemental material for Synthesis, crystal structure and bovine serum albumin–binding studies of a new Cd(II) complex incorporating 2,2′-(propane-1,3-diyl)bis(1H-imidazole-4,5-dicarboxylate)

Supplemental material, Supporting_Information for Synthesis, crystal structure and bovine serum albumin–binding studies of a new Cd(II) complex incorporating 2,2′-(propane-1,3-diyl)bis(1H-imidazole-4,5-dicarboxylate) by Xiao-Fei Li, Li-Gang Ma, Yan-Qiu Yang, Yan-Ju Liu, Xiang-Ru Meng and Huai-Xia Yang in Journal of Chemical Research

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship and/or publication of this article.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by the by programme for the key scientific research project of colleges and universities in Henan Province (grant no. 16A350002) and Henan Province basic and frontier technology research projects (grant no. 152300410214).

ORCID iD

Huai-Xia Yang

Supplemental material

Supplemental material for this article is available online.

References

Shin

Bae

Kim

, et al. Inorg Chem 2013; 52: 2265–2267.

Takaoka

Kawano

Hozumi

, et al. Inorg Chem 2006; 45: 3976–3982.

Kreno

Leong

Farha

, et al. Chem Rev 2012; 112: 1105–1125.

Horcajada

Gref

Baati

, et al. Chem Rev 2012; 112: 1232–1268.

Cheng

Zhang

Wang

, et al. J Chem Res 2018; 42: 575–578.

Yang

Liang

Hao

, et al. J Solid State Chem 2014; 218: 23–31.

Neira

García

Peinador

, et al. J Org Chem 2019; 84: 2325–2329.

Loukopoulos

Kostakis

GE.

Coord Chem Rev 2019; 395: 193–229.

Cheng

Meng

, et al. Acta Cryst 2019; C75: 643–649.

10.

Huang

Wang

, et al. J Coord Chem 2015; 68: 88–105.

11.

Jazestani

Chiniforoshan

Tabrizi

, et al. Inorg Chim Acta 2016; 450: 402–410.

12.

Tahmasian

Safarifard

Morsali

, et al. Polyhedron 2014; 67: 81–88.

13.

Cheng

Liu

Cheng

, et al. J Chem Res 2018; 42: 490–493.

14.

Wang

Niu

Gao

, et al. Cryst Growth Des 2010; 10: 4050–4059.

15.

Niu

, et al. Cryst Growth Des 2009; 9: 3423–3431.

16.

Liu

Cheng

, et al. Acta Cryst 2018; C74: 599–603.

17.

Xiu

, et al. J Coord Chem 2012; 65: 3111–3121.

18.

Yang

Zhou

Jin

, et al. Acta Cryst 2011; E67: m560.

19.

Jin

, et al. Acta Cryst 2011; E67: m988.

20.

Acta Cryst 2012; E68: m1199–m1200.

21.

Liu

Acta Cryst 2012; E68: m1109–m1110.

22.

Sheldrich

GM.

Acta Cryst 2008; A64: 112–122.

23.

Sheldrich

GM.

Acta Cryst 2015; C71: 3–8.

24.

Zhang

Zhou

, et al. Inorg Chim Acta 2014; 421: 45–51.

25.

Roy

Mukherjee

PS.

CrystEngComm 2013; 15: 9596–9602.

26.

Machicote

Pacheco

Bruzzone

Spectrochim Acta 2010; A77: 466–472.

27.

Ding

Huang

Lin

, et al. Dyes Pigments 2009; 82: 65–70.

28.

Cui

Wang

Cui

, et al. Anal Chim Acta 2006; 571: 175–183.

29.

Khodarahmi

Karimi

Kooshk

MRA

, et al. Spectrochim Acta 2012; A89: 177–186.

30.

Jahanban-Esfahlan

Panahi-Azar

Food Chem 2016; 202: 426–431.

31.

Wang

Yan

Zhang

, et al. Z Naturforsch 2013; 68b: 1225–1232.

Supplementary Material

Please find the following supplemental material available below.

For Open Access articles published under a Creative Commons License, all supplemental material carries the same license as the article it is associated with.

For non-Open Access articles published, all supplemental material carries a non-exclusive license, and permission requests for re-use of supplemental material or any part of supplemental material shall be sent directly to the copyright owner as specified in the copyright notice associated with the article.

0.00 MB

0.19 MB

Synthesis,crystal structure and bovine serum albumin–binding studies of a new Cd(II) complex incorporating 2,2′-(propane-1,3-diyl)bis(1H-imidazole-4,5-dicarboxylate)

Abstract

Keywords

Introduction

Experimental

General information and materials

Synthesis of [Cd(H4pbidc)(H2O)] n (1)

Preparation of stock solutions

Single-crystal structure determination

Results and discussion

Crystal structure of [Cd(H4pbidc)(H2O)] n (1)

Fluorescence quenching spectra and quenching mechanism

Binding parameter and binding mode

Conclusion

Supplemental Material

Supporting_Information – Supplemental material for Synthesis, crystal structure and bovine serum albumin–binding studies of a new Cd(II) complex incorporating 2,2′-(propane-1,3-diyl)bis(1H-imidazole-4,5-dicarboxylate)

Footnotes

Declaration of conflicting interests

Funding

ORCID iD

Supplemental material

References

Supplementary Material

Synthesis of [Cd(H₄pbidc)(H₂O)]_n (1)

Crystal structure of [Cd(H₄pbidc)(H₂O)]_n (1)