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Mononuclear gold(I) acetylide complexes with carbonyl moiety: Synthesis, characterization, and tunable emission energy
Journal Pre-proofs Mononuclear Gold(I) Acetylide Complexes with Carbonyl Moiety: Synthesis, Characterization, and Tunable Emission Energy Liu-Ping Yang, Cheng-Luan Li, Yue-Liang Yao, Zhuo-Jia Lin, Zheng-Ping Qiao, Hsiu-Yi Chao PII: DOI: Reference:
S1387-7003(19)30902-5 https://doi.org/10.1016/j.inoche.2019.107731 INOCHE 107731
To appear in:
Inorganic Chemistry Communications
Received Date: Revised Date: Accepted Date:
3 October 2019 9 December 2019 15 December 2019
Please cite this article as: L-P. Yang, C-L. Li, Y-L. Yao, Z-J. Lin, Z-P. Qiao, H-Y. Chao, Mononuclear Gold(I) Acetylide Complexes with Carbonyl Moiety: Synthesis, Characterization, and Tunable Emission Energy, Inorganic Chemistry Communications (2019), doi: https://doi.org/10.1016/j.inoche.2019.107731
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Mononuclear Gold(I) Acetylide Complexes with Carbonyl Moiety: Synthesis, Characterization, and Tunable Emission Energy
Liu-Ping Yanga,b, Cheng-Luan Lia, Yue-Liang Yaoa, Zhuo-Jia Lina, Zheng-Ping Qiaoa, Hsiu-Yi Chaoa,b*
aMOE
Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry,
Sun Yat-Sen University, Guangzhou 510275, P. R. China bGuangzhou
Mecart Smart Technology Research Institute, Guangzhou, 510275, P. R.
China
*Corresponding author. E-mail address: [email protected] (H. -Y. Chao)
1
Abstract A series of gold(I) acetylide complexes, Cy3PAuCCC6H4-C(O)R-4 (R = H (1), Me (2), OMe (3), NH2 (4)) (Cy3P = tricyclohexylphosphine), have been synthesized and characterized. The crystal structures of Cy3PAuCCC6H4-C(O)H-4 (1) and Cy3PAuCCC6H4-C(O)NH2-4 (4) were determined by X-ray diffraction. The photophysical properties of complexes 14 have been studied. Complexes 14 show luminescence both in the solid state and in acetonitrile solution at 298 K, and their emission energies are in the order: 4 > 3 > 2 > 1.
Keywords: Acetylide; Crystal structure; Gold; Luminescence; Synthesis
2
Gold(I) acetylide complexes have attracted much attention due to their novel structures [1] and potential applications in luminescence [1c, 2], mechanochromism [3], medicine [4], catalysis [5], nonlinear optics [6], liquid crystals [7], ion sensors [8], and memory devices [9]. The structureluminescence relationship of gold(I) acetylide complexes with phosphine ligands have been investigated by several groups, and the emission is assigned to come from the 3[(AuP) *(phosphine)], 3[σ(AuP)→*(acetylide
ligand)], 3[d* p], or acetylide ligand-centered 3[
*] excited state [2]. Che and co-workers have previously studied the luminescence properties of gold(I) complexes with oligo(o-, m-, and p-phenyleneethynylene) ligands and found that the triplet emission of the acetylide ligands can be “switched on” through the coordination to [Au(PCy3)]+ and thus the emission energy can be easily tuned by changing the length of the -conjugation of the acetylide ligands [2f, 2g]. Tricyclohexylphosphine is used as an ancillary ligand for spectroscopic benefit since it does not have low-lying ligand-localized excited states and its large cone angle (170) [10] precludes the gold-gold and - interactions, which could affect the lowest-lying excited state. With our continuous interest in the study of structureluminescence relationship of metal acetylide complexes [8b, 8c, 8d, 11], a series of gold(I) acetylide complexes, Cy3PAuCCC6H4-C(O)R-4 (R = H (1), Me (2), OMe (3), NH2 (4)), have been synthesized and characterized. We envisaged that if the substituent R could change the energies of the lowest-lying 3(*) excited states of the acetylide ligands, the emission energies of the gold(I) acetylide complexes may be tuned. The substituent effect (electron-donating ability) of the acetylide ligands 3
on the emission energies of trinuclear copper(I) acetylide complexes [Cu3(μdppm)3(μ3-η1-C≡CC(O)R)2](ClO4) has been previously studied by us and the emission energies increase as the electron-donating ability of R increases [11d]. In this work, the C(O)R group is introduced into the phenyl acetylide ligand and to the best of our knowledge, the systematic study of the luminescence properties of this class of gold(I) acetylide complexes has not been reported in the literature. In this paper, we report the synthesis and photophysical properties of a family of gold(I) acetylide complexes 14. The X-ray crystal structures of Cy3PAuCCC6H4-C(O)H-4 (1) and Cy3PAuCCC6H4-C(O)NH2-4 (4) have been determined. Gold(I) acetylide complexes, Cy3PAuCCC6H4-C(O)R-4 (R = H (1), Me (2), OMe (3), NH2 (4)), were synthesized by the reactions of Cy3PAuCl with corresponding Me3SiC≡CC6H4-C(O)R-4 in a molar ratio of 1:1 in the presence of an excess of KF in dichloromethane/methanol mixture at 298 K. All these gold(I) acetylide complexes gave satisfactory elemental analyses and were characterized by positive ESIMS, IR, 1H, 13C{1H},
and 31P{1H} NMR spectroscopy. They are air-stable in the solid state at
298 K. The IR spectra of the gold(I) acetylide complexes 14 reveal two bands at 20892114 cm1 and 16701717 cm1, characteristic of the (CC) and (C=O) stretches of acetylide ligands, respectively. The 1H NMR spectra of complexes 14 in CDCl3 display multiples at ca. 1.252.01 ppm, which are assigned as the resonances of the protons on the cyclohexyl groups of the phosphine ligand. The doublets appeared at 7.507.87 ppm with the coupling constant of ca. 8 Hz are attributed to 4
the protons on the phenyl rings of complexes 14. In addition, the peaks at 9.92, 2.56, 3.87, and 5.64 (5.99) ppm are attributed to the protons on C(O)R groups (R = H, Me, OMe, and NH2) of complexes 14, respectively. The 13C{1H} NMR spectra of complexes 14 in CDCl3 exhibit two doublets at ca. 140 (2JCP ≈131 Hz) and 102 (3JCP ≈ 25 Hz) ppm, which are assigned to the C and C of the acetylide ligands, respectively. Additionally, a singlet appeared at 166.5191.2 ppm are attributed to the carbon nucleus of the carbonyl groups on complexes 14. The 31P{1H} NMR spectra of the gold(I) acetylide complexes 14 in CDCl3 show a singlet at ca. 57.3 ppm, which is shifted downfield from that of the starting material, Cy3PAuCl (55.2 ppm). The crystal structures of the gold(I) acetylide complexes Cy3PAuCCC6H4-C(O)H-4 (1) and Cy3PAuCCC6H4-C(O)NH2-4 (4) have been determined by X-ray crystallography, and they are shown in Fig. S1 (Supplementary material) and Fig. 1, respectively. Their crystallographic data as well as selected bond distances and angles are listed in Table S1 (Supplementary material) and Table 1, respectively. The Au(I) coordination geometry in 1 and 4 are nearly linear with the PAuC angles of 175.39(10)° and 174.52(8)°, respectively. The AuP bond distances (2.2952(11) and 2.2900(11) Å for 1 and 4, respectively) are similar to those reported for other gold(I) arylacetylide complexes with tricyclohexylphosphine ligand [2g, 2h, 8d]. The AuC (2.018(4) and 2.051(3) Å) and C(1)C(2) (1.193(5) and 1.157(5) Å) distances of 1 and 4 also resemble those in analogous gold(I) acetylide complexes [2g, 2h, 8d]. No close gold···gold contact (< 3.5 Å) were observed in 1 and 4. This could be due to the steric 5
hindrance of the cyclohexyl group of the phosphine ligand (cone angle = 170) [10]. In 1, there are weak intermolecular CH···(CC) contacts between H(2) of the phenyl ring of the acetylide ligand and CC (C(1a) and C(2a)) of the acetylide ligand (H(2)···C(1a) 2.701 Å; H(2)···C(2a) 2.887 Å; C(5)H(2)···C(1a) 146°; C(5)H(2)···C(2a) 161°) (Fig. S2, Supplementary material). In addition, there are close contacts between H(1) of the phenyl ring of the acetylide ligand and Au(1a) (H(1)···Au(1a) 2.880 Å; C(4)H(1)···Au(1a) 141°). In 4, weak intermolecular NH···(CC) contacts between H(5) of amide group of the acetylide ligand and CC (C(1b) and C(2b)) of the acetylide ligand (H(5)···C(1b) 2.717 Å; H(5)···C(2b) 2.899 Å; N(1)H(5)···C(1b) 144°; N(1)H(5)···C(2b) 163°) are observed (Fig. 2). Additionally, there are intermolecular hydrogen bonding interactions between hydrogen atoms of amide groups and oxygen atoms of carbonyl groups in acetylide ligands of 4 (Fig. 2). The hydrogen bonding parameters of 4 are listed in Table S2 (Supplementary Material). The photophysical data for complexes 14 are summarized in Table 2. For comparison, the photophysical data of corresponding free acetylide ligands are listed in Table S3 (Supplementary Material). Fig. S3 (Supplementary Material) displays the electronic absorption spectra of complexes 14 in dichloromethane at 298 K. 6
Complexes 14 show absorption bands at 288320 nm, which are all red-shifted compared to those of free acetylide ligands (267294 nm). The red-shift could come from the orbital interaction between the acetylide ligand and Au 5d orbitals [2h]. The absorption peak maxima of Cy3PAuCCC6H4C(O)R (complexes 14) depend on the nature of substituent R on the acetylide ligands and the absorption energies of complexes 14 increase in the order: 1 < 2 < 3 < 4. The same trend is also observed in their corresponding free trimethylsilylacetylide ligands (Table S3, Supplementary Material). The spacings of adjacent absorption maxima for complexes 14 and the acetylide ligands are in the range of 11001700 cm1. Thus, the absorption bands of complexes 14 at 288320 nm are assigned as the * transitions of the acetyilde ligands. The energies of 1(*) transitions of the acetyilde ligands on 1 (308 and 320 nm) and 2 (302 and 314 nm) in dichloromethane at 298 K are lower than those of their analogues Cy3PAuCCC6H5 (267, 281, and 290 nm) and Cy3PAuCCC6H4CH3 (269, 281, and 290 nm) [2g].
Excitation of complexes 14 both in the solid state and in dichloromethane solution at > 330 nm produces luminescence in the visible light regime. Fig. 3 display the emission spectra of complexes 1 in the solid state at 298 K (for the emission spectra of complexes 24 in the solid state at 298 K, see Figures S4S6 (Supplementary Material), respectively). The solid state emission spectra of
7
complexes 14 show vibronic fine structures at 450569 nm with the progressional spacings of three different frequencies, ca. 1100, 1600, and 2100 cm1, which are attributed to the phenyl ring deformation, symmetric phenyl ring stretch, and CC stretching frequencies of the ground state, respectively [2g, 2h]. These spacings have also been observed for other gold(I) acetylide complexes [2g, 2h]. The observed large Stokes shifts together with long lifetimes in the microsecond region of the emission suggest the origin of the emissions have triplet parentage. The emission maxima for complexes 14 in the solid state at 298 K increase in the order: 1 < 2 < 3 < 4 (Table 2). The same order is also observed for their emission maxima in dichloromethane solution at 298 K (Fig. 4). Therefore, the lowest-lying emissive state of complexes 14 is assigned as the 3(*) excited states of the acetylide ligands. The emission energy is higher when the electron-donating ability of the substituent R on the acetylide ligand is stronger: (R = NH2 (4) > OCH3 (3) > CH3 (2) > H (1)). This could be due to increase of energy gap between HOMO (predominantly localized on the orbital of the acetylide ligand) and LUMO (predominantly localized on the * orbital of the acetylide ligand) when the electron-donating ability of substituent R increases. Compared with the emission energies of other structure-related gold(I) acetylide complexes reported in the literature, the solid samples of complexes 1 and 2 at 298 K have lower emission energies (477 and 474 nm for 1 and 2, respectively) than their analogues Cy3PAuCCC6H5 (421 nm) and Cy3PAuCCC6H4CH3 (422 nm) [2g]. Thus, the introduction of carbonyl group would reduce the energy gap of * transition of the acetylide ligand since the length of -conjugation system increases. This 8
observation also supports the assignment of 3(*) excited states of the acetylide ligands for the emission origin of complexes 14. In summary, a series of mononuclear gold(I) acetylide complexes, Cy3PAuCCC6H4C(O)R (R = H, Me, OMe, NH2), have been synthesized and characterized. Through the coordination to Au(PCy3)+ the emission from 3(*) excited states of the acetylide ligands could be switched on. The 3(*) emission energies of complexes 14 could be tuned by changing the electron-donating ability of the substituent R on the acetylide ligands and they are in the order: R = H (1) < Me (2) < OMe (3) < NH2 (4).
Appendix A. Supplementary material CCDC 1951318 and 1951319 contain the supplementary crystallographic data for 1 and 4. These data can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retreving.html, or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336 033; or [email protected]. Supplementary data associated with this article can be found, in the online version, at: doi:10.1016/j.inoche.xxxx.xxxxxx
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Acknowledgment We are grateful for financial support from Natural Science Foundation of China (20971131). We thank Prof. Jiaobing Wang for help of getting the 13C NMR data.
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Figure captions: Fig. 1. A view of crystal structure of 4 with the atomic numbering scheme. All hydrogen atoms are omitted for clarity. Fig. 2. Intermolecular CH···(CC) and hydrogen bonding interactions in 4. Fig. 3. Emission spectrum of 1 in the solid state at 298 K (ex = 300 nm). Fig. 4. Normalized emission spectra of 14 in CH2Cl2 at 298 K (ex = 315 nm).
19
Fig. 1
20
Fig. 2
21
Emission intensity (a. u)
Fig. 3
450
500
550
Wavelength / nm
22
600
650
Normalized emission intensity (a. u.)
Fig. 4
1 2 3 4
450
500
550
Wavelength / nm
23
600
Table 1. Selected bond lengths (Å) and angles () for 1 and 4 1
4
Au(1)C(1)
2.018(4)
Au(1)C(1)
2.051(3)
Au(1)P(1)
2.2952(11)
Au(1)P(1)
2.2900(11)
C(1)C(2)
1.193(5)
C(1)C(2)
1.157(5)
C(9)O(1)
1.204(5)
C(9)O(1)
1.235(4)
P(1)Au(1)C(1)
175.39(10)
P(1)Au(1)C(1)
174.52(8)
Au(1)C(1)C(2)
176.6(3)
Au(1)C(1)C(2)
169.7(3)
C(1)C(2)C(3)
176.5(4)
C(1)C(2)C(3)
179.7(4)
24
Table 2. Photophysical data for 14
Complex Medium (T / K) 1
CH2Cl2 (298)
abs / nm (ε / dm3 mol1 cm1)
em / nm (τ0 / μs)
308 (sh, 29100), 320 (36000)
483 (max, 70.4), 517 (66.5)
Solid (298)
em (%)
5.3
477 (max,133.5), 505 (130.7), 515 (127.9), 527 (128.4), 548 (131.6), 562 (124.1)
2
CH2Cl2 (298)
302 (27900), 314 (30900)
Solid (298) 3
CH2Cl2 (298)
CH2Cl2 (298) Solid (298)
6.3
474 (39.1), 507 (max, 42.2), 550 (37.4), 569 (35.1) 290 (22900), 305 (27000)
Solid (298) 4
474 (max, 51.2), 508(48.2)
456 (max, 50.1), 486 (47.3)
3.2
458 (max,146.9), 484 (139.2), 493 (137.1), 506 (141.2) 288 (32100), 302 (34400)
452 (max, 51.0), 485 (45.6) 450 (48.8), 493 (max, 52.7), 521(50.9), 536 (46.3), 552 (49.7)
25
6.1
Highlights: 1. A series of mononuclear gold(I) acetylide complexes bearing carbonyl group, 14, have been synthesized. 2. The emission origin of complexes 14 comes from the 3(*) excited states of the acetylide ligands. 3. The emission energies of complexes 14 can be tuned by changing the substituents R on the acetylide ligands.
Normalized emission intensity (a. u.)
Graphic Abstract:
R H Me OMe NH2
450
500
550
600
Wavelength / nm
26
Declaration of interests
☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:
27
Liu-Ping Yang: Validation, Investigation, Visualization Cheng-Luan Li: Investigation, Visualization Yue-Liang Yao: Investigation Zhuo-Jia Lin: Investigation Zheng-Ping Qiao: Writing - Review & Editing Hsiu-Yi Chao: Conceptualization, Writing - Original Draft, Writing - Review & Editing, Supervision
28
S1387-7003(19)30902-5 https://doi.org/10.1016/j.inoche.2019.107731 INOCHE 107731
To appear in:
Inorganic Chemistry Communications
Received Date: Revised Date: Accepted Date:
3 October 2019 9 December 2019 15 December 2019
Please cite this article as: L-P. Yang, C-L. Li, Y-L. Yao, Z-J. Lin, Z-P. Qiao, H-Y. Chao, Mononuclear Gold(I) Acetylide Complexes with Carbonyl Moiety: Synthesis, Characterization, and Tunable Emission Energy, Inorganic Chemistry Communications (2019), doi: https://doi.org/10.1016/j.inoche.2019.107731
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© 2019 Published by Elsevier B.V.
Mononuclear Gold(I) Acetylide Complexes with Carbonyl Moiety: Synthesis, Characterization, and Tunable Emission Energy
Liu-Ping Yanga,b, Cheng-Luan Lia, Yue-Liang Yaoa, Zhuo-Jia Lina, Zheng-Ping Qiaoa, Hsiu-Yi Chaoa,b*
aMOE
Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry,
Sun Yat-Sen University, Guangzhou 510275, P. R. China bGuangzhou
Mecart Smart Technology Research Institute, Guangzhou, 510275, P. R.
China
*Corresponding author. E-mail address: [email protected] (H. -Y. Chao)
1
Abstract A series of gold(I) acetylide complexes, Cy3PAuCCC6H4-C(O)R-4 (R = H (1), Me (2), OMe (3), NH2 (4)) (Cy3P = tricyclohexylphosphine), have been synthesized and characterized. The crystal structures of Cy3PAuCCC6H4-C(O)H-4 (1) and Cy3PAuCCC6H4-C(O)NH2-4 (4) were determined by X-ray diffraction. The photophysical properties of complexes 14 have been studied. Complexes 14 show luminescence both in the solid state and in acetonitrile solution at 298 K, and their emission energies are in the order: 4 > 3 > 2 > 1.
Keywords: Acetylide; Crystal structure; Gold; Luminescence; Synthesis
2
Gold(I) acetylide complexes have attracted much attention due to their novel structures [1] and potential applications in luminescence [1c, 2], mechanochromism [3], medicine [4], catalysis [5], nonlinear optics [6], liquid crystals [7], ion sensors [8], and memory devices [9]. The structureluminescence relationship of gold(I) acetylide complexes with phosphine ligands have been investigated by several groups, and the emission is assigned to come from the 3[(AuP) *(phosphine)], 3[σ(AuP)→*(acetylide
ligand)], 3[d* p], or acetylide ligand-centered 3[
*] excited state [2]. Che and co-workers have previously studied the luminescence properties of gold(I) complexes with oligo(o-, m-, and p-phenyleneethynylene) ligands and found that the triplet emission of the acetylide ligands can be “switched on” through the coordination to [Au(PCy3)]+ and thus the emission energy can be easily tuned by changing the length of the -conjugation of the acetylide ligands [2f, 2g]. Tricyclohexylphosphine is used as an ancillary ligand for spectroscopic benefit since it does not have low-lying ligand-localized excited states and its large cone angle (170) [10] precludes the gold-gold and - interactions, which could affect the lowest-lying excited state. With our continuous interest in the study of structureluminescence relationship of metal acetylide complexes [8b, 8c, 8d, 11], a series of gold(I) acetylide complexes, Cy3PAuCCC6H4-C(O)R-4 (R = H (1), Me (2), OMe (3), NH2 (4)), have been synthesized and characterized. We envisaged that if the substituent R could change the energies of the lowest-lying 3(*) excited states of the acetylide ligands, the emission energies of the gold(I) acetylide complexes may be tuned. The substituent effect (electron-donating ability) of the acetylide ligands 3
on the emission energies of trinuclear copper(I) acetylide complexes [Cu3(μdppm)3(μ3-η1-C≡CC(O)R)2](ClO4) has been previously studied by us and the emission energies increase as the electron-donating ability of R increases [11d]. In this work, the C(O)R group is introduced into the phenyl acetylide ligand and to the best of our knowledge, the systematic study of the luminescence properties of this class of gold(I) acetylide complexes has not been reported in the literature. In this paper, we report the synthesis and photophysical properties of a family of gold(I) acetylide complexes 14. The X-ray crystal structures of Cy3PAuCCC6H4-C(O)H-4 (1) and Cy3PAuCCC6H4-C(O)NH2-4 (4) have been determined. Gold(I) acetylide complexes, Cy3PAuCCC6H4-C(O)R-4 (R = H (1), Me (2), OMe (3), NH2 (4)), were synthesized by the reactions of Cy3PAuCl with corresponding Me3SiC≡CC6H4-C(O)R-4 in a molar ratio of 1:1 in the presence of an excess of KF in dichloromethane/methanol mixture at 298 K. All these gold(I) acetylide complexes gave satisfactory elemental analyses and were characterized by positive ESIMS, IR, 1H, 13C{1H},
and 31P{1H} NMR spectroscopy. They are air-stable in the solid state at
298 K. The IR spectra of the gold(I) acetylide complexes 14 reveal two bands at 20892114 cm1 and 16701717 cm1, characteristic of the (CC) and (C=O) stretches of acetylide ligands, respectively. The 1H NMR spectra of complexes 14 in CDCl3 display multiples at ca. 1.252.01 ppm, which are assigned as the resonances of the protons on the cyclohexyl groups of the phosphine ligand. The doublets appeared at 7.507.87 ppm with the coupling constant of ca. 8 Hz are attributed to 4
the protons on the phenyl rings of complexes 14. In addition, the peaks at 9.92, 2.56, 3.87, and 5.64 (5.99) ppm are attributed to the protons on C(O)R groups (R = H, Me, OMe, and NH2) of complexes 14, respectively. The 13C{1H} NMR spectra of complexes 14 in CDCl3 exhibit two doublets at ca. 140 (2JCP ≈131 Hz) and 102 (3JCP ≈ 25 Hz) ppm, which are assigned to the C and C of the acetylide ligands, respectively. Additionally, a singlet appeared at 166.5191.2 ppm are attributed to the carbon nucleus of the carbonyl groups on complexes 14. The 31P{1H} NMR spectra of the gold(I) acetylide complexes 14 in CDCl3 show a singlet at ca. 57.3 ppm, which is shifted downfield from that of the starting material, Cy3PAuCl (55.2 ppm). The crystal structures of the gold(I) acetylide complexes Cy3PAuCCC6H4-C(O)H-4 (1) and Cy3PAuCCC6H4-C(O)NH2-4 (4) have been determined by X-ray crystallography, and they are shown in Fig. S1 (Supplementary material) and Fig. 1, respectively. Their crystallographic data as well as selected bond distances and angles are listed in Table S1 (Supplementary material) and Table 1, respectively. The Au(I) coordination geometry in 1 and 4 are nearly linear with the PAuC angles of 175.39(10)° and 174.52(8)°, respectively. The AuP bond distances (2.2952(11) and 2.2900(11) Å for 1 and 4, respectively) are similar to those reported for other gold(I) arylacetylide complexes with tricyclohexylphosphine ligand [2g, 2h, 8d]. The AuC (2.018(4) and 2.051(3) Å) and C(1)C(2) (1.193(5) and 1.157(5) Å) distances of 1 and 4 also resemble those in analogous gold(I) acetylide complexes [2g, 2h, 8d]. No close gold···gold contact (< 3.5 Å) were observed in 1 and 4. This could be due to the steric 5
hindrance of the cyclohexyl group of the phosphine ligand (cone angle = 170) [10]. In 1, there are weak intermolecular CH···(CC) contacts between H(2) of the phenyl ring of the acetylide ligand and CC (C(1a) and C(2a)) of the acetylide ligand (H(2)···C(1a) 2.701 Å; H(2)···C(2a) 2.887 Å; C(5)H(2)···C(1a) 146°; C(5)H(2)···C(2a) 161°) (Fig. S2, Supplementary material). In addition, there are close contacts between H(1) of the phenyl ring of the acetylide ligand and Au(1a) (H(1)···Au(1a) 2.880 Å; C(4)H(1)···Au(1a) 141°). In 4, weak intermolecular NH···(CC) contacts between H(5) of amide group of the acetylide ligand and CC (C(1b) and C(2b)) of the acetylide ligand (H(5)···C(1b) 2.717 Å; H(5)···C(2b) 2.899 Å; N(1)H(5)···C(1b) 144°; N(1)H(5)···C(2b) 163°) are observed (Fig. 2). Additionally, there are intermolecular hydrogen bonding interactions between hydrogen atoms of amide groups and oxygen atoms of carbonyl groups in acetylide ligands of 4 (Fig. 2). The hydrogen bonding parameters of 4 are listed in Table S2 (Supplementary Material).
Complexes 14 show absorption bands at 288320 nm, which are all red-shifted compared to those of free acetylide ligands (267294 nm). The red-shift could come from the orbital interaction between the acetylide ligand and Au 5d orbitals [2h]. The absorption peak maxima of Cy3PAuCCC6H4C(O)R (complexes 14) depend on the nature of substituent R on the acetylide ligands and the absorption energies of complexes 14 increase in the order: 1 < 2 < 3 < 4. The same trend is also observed in their corresponding free trimethylsilylacetylide ligands (Table S3, Supplementary Material). The spacings of adjacent absorption maxima for complexes 14 and the acetylide ligands are in the range of 11001700 cm1. Thus, the absorption bands of complexes 14 at 288320 nm are assigned as the * transitions of the acetyilde ligands. The energies of 1(*) transitions of the acetyilde ligands on 1 (308 and 320 nm) and 2 (302 and 314 nm) in dichloromethane at 298 K are lower than those of their analogues Cy3PAuCCC6H5 (267, 281, and 290 nm) and Cy3PAuCCC6H4CH3 (269, 281, and 290 nm) [2g].
7
complexes 14 show vibronic fine structures at 450569 nm with the progressional spacings of three different frequencies, ca. 1100, 1600, and 2100 cm1, which are attributed to the phenyl ring deformation, symmetric phenyl ring stretch, and CC stretching frequencies of the ground state, respectively [2g, 2h]. These spacings have also been observed for other gold(I) acetylide complexes [2g, 2h]. The observed large Stokes shifts together with long lifetimes in the microsecond region of the emission suggest the origin of the emissions have triplet parentage. The emission maxima for complexes 14 in the solid state at 298 K increase in the order: 1 < 2 < 3 < 4 (Table 2). The same order is also observed for their emission maxima in dichloromethane solution at 298 K (Fig. 4). Therefore, the lowest-lying emissive state of complexes 14 is assigned as the 3(*) excited states of the acetylide ligands. The emission energy is higher when the electron-donating ability of the substituent R on the acetylide ligand is stronger: (R = NH2 (4) > OCH3 (3) > CH3 (2) > H (1)). This could be due to increase of energy gap between HOMO (predominantly localized on the orbital of the acetylide ligand) and LUMO (predominantly localized on the * orbital of the acetylide ligand) when the electron-donating ability of substituent R increases. Compared with the emission energies of other structure-related gold(I) acetylide complexes reported in the literature, the solid samples of complexes 1 and 2 at 298 K have lower emission energies (477 and 474 nm for 1 and 2, respectively) than their analogues Cy3PAuCCC6H5 (421 nm) and Cy3PAuCCC6H4CH3 (422 nm) [2g]. Thus, the introduction of carbonyl group would reduce the energy gap of * transition of the acetylide ligand since the length of -conjugation system increases. This 8
observation also supports the assignment of 3(*) excited states of the acetylide ligands for the emission origin of complexes 14.
Appendix A. Supplementary material CCDC 1951318 and 1951319 contain the supplementary crystallographic data for 1 and 4. These data can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retreving.html, or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336 033; or [email protected]. Supplementary data associated with this article can be found, in the online version, at: doi:10.1016/j.inoche.xxxx.xxxxxx
9
Acknowledgment We are grateful for financial support from Natural Science Foundation of China (20971131). We thank Prof. Jiaobing Wang for help of getting the 13C NMR data.
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Figure captions: Fig. 1. A view of crystal structure of 4 with the atomic numbering scheme. All hydrogen atoms are omitted for clarity. Fig. 2. Intermolecular CH···(CC) and hydrogen bonding interactions in 4. Fig. 3. Emission spectrum of 1 in the solid state at 298 K (ex = 300 nm). Fig. 4. Normalized emission spectra of 14 in CH2Cl2 at 298 K (ex = 315 nm).
19
Fig. 1
20
Fig. 2
21
Emission intensity (a. u)
Fig. 3
450
500
550
Wavelength / nm
22
600
650
Normalized emission intensity (a. u.)
Fig. 4
1 2 3 4
450
500
550
Wavelength / nm
23
600
Table 1. Selected bond lengths (Å) and angles () for 1 and 4 1
4
Au(1)C(1)
2.018(4)
Au(1)C(1)
2.051(3)
Au(1)P(1)
2.2952(11)
Au(1)P(1)
2.2900(11)
C(1)C(2)
1.193(5)
C(1)C(2)
1.157(5)
C(9)O(1)
1.204(5)
C(9)O(1)
1.235(4)
P(1)Au(1)C(1)
175.39(10)
P(1)Au(1)C(1)
174.52(8)
Au(1)C(1)C(2)
176.6(3)
Au(1)C(1)C(2)
169.7(3)
C(1)C(2)C(3)
176.5(4)
C(1)C(2)C(3)
179.7(4)
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Table 2. Photophysical data for 14
Complex Medium (T / K) 1
CH2Cl2 (298)
abs / nm (ε / dm3 mol1 cm1)
em / nm (τ0 / μs)
308 (sh, 29100), 320 (36000)
483 (max, 70.4), 517 (66.5)
Solid (298)
em (%)
5.3
477 (max,133.5), 505 (130.7), 515 (127.9), 527 (128.4), 548 (131.6), 562 (124.1)
2
CH2Cl2 (298)
302 (27900), 314 (30900)
Solid (298) 3
CH2Cl2 (298)
CH2Cl2 (298) Solid (298)
6.3
474 (39.1), 507 (max, 42.2), 550 (37.4), 569 (35.1) 290 (22900), 305 (27000)
Solid (298) 4
474 (max, 51.2), 508(48.2)
456 (max, 50.1), 486 (47.3)
3.2
458 (max,146.9), 484 (139.2), 493 (137.1), 506 (141.2) 288 (32100), 302 (34400)
452 (max, 51.0), 485 (45.6) 450 (48.8), 493 (max, 52.7), 521(50.9), 536 (46.3), 552 (49.7)
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6.1
Highlights: 1. A series of mononuclear gold(I) acetylide complexes bearing carbonyl group, 14, have been synthesized. 2. The emission origin of complexes 14 comes from the 3(*) excited states of the acetylide ligands. 3. The emission energies of complexes 14 can be tuned by changing the substituents R on the acetylide ligands.
Normalized emission intensity (a. u.)
Graphic Abstract:
R H Me OMe NH2
450
500
550
600
Wavelength / nm
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Declaration of interests
☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:
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Liu-Ping Yang: Validation, Investigation, Visualization Cheng-Luan Li: Investigation, Visualization Yue-Liang Yao: Investigation Zhuo-Jia Lin: Investigation Zheng-Ping Qiao: Writing - Review & Editing Hsiu-Yi Chao: Conceptualization, Writing - Original Draft, Writing - Review & Editing, Supervision
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