Coordination-Driven Salamo-Salen-Salamo-Type Multinuclear Transition Metal(II) Complexes: Synthesis, Structure, Luminescence, Transformation of Configuration, and Nuclearity Induced by the Acetylacetone Anion.

A flexible polydentate Salamo-Salen-Salamo hybrid ligand H4L was designed and synthesized, which has rich pockets (salamo and salen pockets) so that it may have fascinating coordination patterns with transition metal(II) ions. Four multinuclear transition metal(II) complexes, novel butterfly-shaped homotetranuclear [Ni4(L)(µ1-OAc)2(µ1,3-OAc)2(H2O)0.5(CH3CH2OH)3.5]·4CH3CH2OH (1), helical homotrinuclear [Zn3(L)(µ1-OAc)2]·2CH3CH2OH (2), double-helical homotrinuclear [Cu2(H2L)2]·2CH3CN (3), and mononuclear [Ni(H2L)]·1.5CH3COCH3 (4), have been synthesized and characterized by single-crystal X-ray diffraction. The effects of different anions [OAc- and (O2C5H7)2-] on the complexation behavior of H4L with transition metal(II) ions were studied by UV-vis spectrophotometry. The fluorescent properties of the four complexes were studied with zebrafish, which are expected to be a potential light-emitting material. Ultimately, interaction region indicator (IRI) valuations, Hirshfeld surface analyses, density functional theory (DFT & TD-DFT), electrostatic potential analyses (ESP), and simulations were carried out to further demonstrate the weak interactions and electronic properties of the free ligand and its four complexes.

Exploitation of a Half-Conjugate Polydentate Salamo-Salen Hybrid Ligand and Its Two Phenoxide-Bridged Heterohexanuclear 3d-s Double-Helical Cluster Complexes.

A half-conjugate polydentate Salamo-Salen hybrid ligand, H5L, containing two unique N2O2 pockets was first designed so that these metal ions in the complexes appear in different coordination modes. Two heterohexanuclear 3d-s double-helical cluster complexes, [Zn4Ca2L2(µ1-OAc)2(EtOH)2]·2EtOH (1; EtOH = ethanol) and [Zn4Sr2L2(µ2-OAc)2(MeOH)2]·2CH2Cl2 (2; MeOH = methanol), are reported that are formed through the reaction of H5L with zinc(II) and calcium(II) acetate or strontium(II) acetate, respectively. IR spectral analysis of the two complexes showed the existence of monodentate- and bidentate-coordinated acetate ions. The fluorescence properties of the ligand and its two heterohexanuclear complexes were explored in MeOH and water solutions, separately. In addition, theoretical calculations (density functional theory, interaction region indicator, and bond order) were performed to further understand the formation of a single-molecular double helix and the electron distribution characteristics of the two complexes.

A Bis(Salamo)-Based Fluorogenic Sensor for Highly Selective and Sequential Recognition of Cu2+ and B4O72- Ions in Semi-Aqueous Medium.

A new type of multifunctional bis(salamo)-based fluorogenic sensor H2BS was designed and synthesized. Under the action of VDMF: VH2O = 9: 1, the fluorogenic sensor can identify Cu2+ and B4O72-, in which N and O atoms can serve as binding sites for Cu2+ and B4O72-, the stoichiometry of the binding of the fluorogenic sensor H2BS and Cu2+ has been confirmed by titration experiment, working curve, ESI-MS analysis and DFT calculation. The pH response experiment also confirmed that the fluorogenic sensor can recognize Cu2+ and B4O72- in the pH range applicable to the physiological environment. The minimum detection limit of H2BS for Cu2+ and B4O72- recognition reaches 1.12 × 10-7 and 5.56 × 10-8 M, and the fluorogenic sensor H2BS has been successfully applied to Cu2+ detection in actual water samples, and the test strip for detecting Cu2+ and B4O72- was obtained. Meanwhile, the success of the test strip experiment made the fluorogenic sensor H2BS to recognize Cu2+ and B4O72- widely used in daily life. A new type of salamo-based multifunctional fluorogenic sensor H2BS was designed and synthesized to identify Cu2+ and B4O72- in aqueous solvent systems. Added Cu2+ to H2BS can cause fluorescence quenching. Further experiments showed that H2BS and Cu2+ form a stable 1:2 complex, while B4O72- can also cause fluorescence quenching of H2BS, which is the occurrence of the PET effect. Meanwhile, H2BS can be used for quantitative detection in the environment and rapid identification in life.

Highly efficient detection of Cu2+ and B4 O7 2- based on a recyclable asymmetric salamo-based probe in aqueous medium.

An asymmetric salamo-based probe molecule (H2 L) was synthesized and characterized structurally. When DMF/H2 O (9:1) was used as the solvent, it was shown probe H2 L has high sensitivity to Cu2+ . Using high-resolution mass spectrometry and theoretical calculation, it was found that probe H2 L could form a more stable complex (1:1) with Cu2+ , the minimum limit of detection (LOD) of H2 L for Cu2+ was calculated as 9.95 × 10-8 M. In addition, probe H2 L could also be used to identify B4 O7 2- under the same detection conditions and the minimum LOD of H2 L for B4 O7 2- was calculated as 4.98 × 10-7 M. At the same time, density functional theory theoretical calculation further proved the flexibility of probe H2 L. Through the action of EDTA, probe H2 L had a cyclic ability to recognize Cu2+ , and showed a better response in the physiological pH range; probe H2 L had the characteristics of fast recognition speed and high efficiency. In addition, with probe H2 L test paper for Cu2+ and B4 O7 2- , the effect was more obvious. Meanwhile, probe H2 L can be used to quantitatively detect Cu2+ in water samples.

Oxidative α-Trichloromethylation of Tertiary Amines: An Entry to α-Amino Acid Esters.

α-Trichloromethylation of tertiary amines with trimethyl(trichloromethyl)silane by oxidative coupling, using DDQ as an oxidant, has been realized. The reaction is instantaneous, is scalable, and tolerates a broad range of functional groups and heteroarenes. The trichloromethylated products can be easily converted into ß,ß-dichloroamines, enamines, and α-amino acid esters under operationally simple conditions. This methodology provides an efficient alternative to the poisonous cyanation reactions for the synthesis of carboxylic acid and their derivatives.

Unprecedented Fluorescent Dinuclear CoII and ZnII Coordination Compounds with a Symmetric Bis(salamo)-Like Tetraoxime.

Two unprecedented homometallic CoII and ZnII coordination compounds, [M2(L)(OCH3)][M2(L)(OAc)] (MII = CoII (1) and ZnII (2)), with a novel symmetric bis(salamo)-like tetraoxime ligand H3L were synthesized and characterized by elemental analyses, infrafred (IR), ultraviolet⁻visible spectroscopy (UV-Vis), fluorescent spectra and single-crystal X-ray diffraction analyses. The unit cell of the two coordination compounds contains two crystallographically and chemically independent dinuclear coordination compounds. In the two coordination compounds, three metal ions are five-coordinated, formed two square pyramidal and a trigonal bipyramidal geometries, and the other metal ion is a hexacoordinate octahedral configuration. In addition, the coordination compound 1 forms a 3D supramolecular structure, and the coordination compound 2 forms a 0D dimer structure by the inter-molecular hydrogen bond interactions. Meanwhile, the fluorescence spectra of the coordination compounds 1 and 2 were also measured and discussed.

A Self-Assembled ZnII-NdIII Heterohexanuclear Dimer Based on a Hexadentate N2O4-Type Ligand and Terephthalic Acid: Synthesis, Structure, and Fluorescence Properties.

A self-assembled ZnII-NdIII heterohexanuclear coordination compound [Zn4Nd2(L)4(bdc)2]·2NO3 based on a hexadentate Salamo-like chelating ligand (H2L = 1,2-bis(3-methoxysalicylideneaminooxy)ethane]) and H2bdc (H2bdc = terephthalic acid) has been synthesized and characterized by elemental analyses, IR and UV/Vis spectra, and X-ray crystallography. Two crystallographically equivalent [Zn2Nd(L)2] moieties lie in the inversion center linked by two (bdc)2- ligands leading to a heterohexanuclear dimer in which the carboxylato group bridges the ZnII and NdIII atoms. The heteropolynuclear 3d-4f coordination compound includes four ZnII atoms, two NdIII atoms, four completely deprotonated (L)2- units, two fully deprotonated (bdc)2- units, and two crystalling nitrate ions. All of the ZnII atoms in the ZnII-NdIII coordination compound possess trigonal bipyramidal geometries and the NdIII atoms possess distorted bicapped square antiprism coordination arrangements. In addition, the fluorescence properties of the ligand and the ZnII-NdIII coordination compound were investigated.

Synthesis and Fluorescence Properties of a New Heterotrinuclear Co(II)-Ce(III)Complex Constructed from a bis(salamo)-Type Tetraoxime Ligand.

[Co2(L)Ce(OAc)3(CH3CH2OH)]·1.5CH3OH∙0.5CH2Cl2, a heterotrinuclear Co(II)-Ce(III) bis(salamo)-type complex with a symmetric bi(salamo)-type ligand H4L and an acyclic naphthalenediol moiety, was designed, synthesized and characterized by elemental analyses, FT-IR, UV-Vis and fluorescence spectroscopy and X-ray crystallography. The X-ray crystallographic investigation revealed the heterotrinuclear complex consisted of two Co(II) atoms, one Ce(III) atom, one (L)4‒ unit, three µ2-acetate ions, one coordinated ethanol molecule, one and half crystallization methanol molecule and half crystallization dichloromethane molecule. Two Co(II) atoms located in the N2O2 coordination spheres, are both hexacoordinated, with slightly distorted octahedral geometries. The Ce(III) atom is nine-coordinated and located in the O6 cavity possesses a single square antiprismatic geometry. In addition, supramolecular interactions exist in the Co(II)-Ce(III) complex. Two infinite 2D supramolecular structures are built via intermolecular O-H···O, C-H···O and C-H···π interactions, respectively.

Synthesis and Fluorescence Properties of Structurally Characterized Heterobimetalic Cu(II)⁻Na(I) Bis(salamo)-Based Complex Bearing Square Planar, Square Pyramid and Triangular Prism Geometries of Metal Centers.

A novel heterotrinuclear complex [Cu2(L)Na(µ-NO3)]∙CH3OH∙CHCl3 derived from a symmetric bis(salamo)-type tetraoxime H4L having a naphthalenediol unit, was prepared and structurally characterized via means of elemental analyses, UV-Vis, FT-IR, fluorescent spectra and single-crystal X-ray diffraction. The heterobimetallic Cu(II)⁻Na(I) complex was acquired via the reaction of H4L with 2 equivalents of Cu(NO3)2·2H2O and 1 equivalent of NaOAc. Clearly, the heterotrinuclear Cu(II)⁻Na(I) complex has a 1:2:1 ligand-to-metal (Cu(II) and Na(I)) ratio. X-ray diffraction results exhibited the different geometric behaviors of the Na(I) and Cu(II) atoms in the heterotrinuclear complex; the both Cu(II) atoms are sited in the N2O2 coordination environments of fully deprotonated (L)4− unit. One Cu(II) atom (Cu1) is five-coordinated and possesses a geometry of slightly distorted square pyramid, while another Cu(II) atom (Cu2) is four-coordination possessing a square planar coordination geometry. Moreover, the Na(I) atom is in the O6 cavity and adopts seven-coordination with a geometry of slightly distorted single triangular prism. In addition, there are abundant supramolecular interactions in the Cu(II)⁻Na(I) complex. The fluorescence spectra showed the Cu(II)⁻Na(I) complex possesses a significant fluorescent quenching and exhibited a hypsochromic-shift compared with the ligand H4L.

A unique N-heterocyclic oligo(N,O-donor) salamo-Ni(II)-based probe for highly selective fluorescence detection of Cr2O72.

A unique fluorescent probe Ni-DAS was developed by a nitrogenous heterocyclic oligo(N,O-donor) salamo-based compound DAS. DAS exhibits AIE and ESIPT effects which are extremely infrequent in salamo-based multi-oxime compounds. In addition, Ni-DAS can be used as a fluorescent probe with high selectivity and sensitivity to recognize Cr2O72- in DMF with 80 % water content, which enhances the value of the probe for application in real environments, and outperforms most similar molecular fluorescence probes. The probe Ni-DAS can recognize Cr2O72- by oxidative hydrolysis of C = N bonds, which promotes further research on theory of C = N bond hydrolysis, and the binding ratio and recognition mechanism were verified and supported by relevant theoretical calculations (DFT & MESP). The experiments showed that the probe Ni-DAS can be used for ion detection in real environments. It provides a new strategy for the oxidative hydrolysis of C = N bond and the structure of salamo-based compounds with AIE nature, and offers new ideas for study ion recognition and acidity detection.

An unusual highly sensitive dual-channel bis(salamo)-like chemical probe for recognizing B4O72-, sensing mechanism, theoretical calculations and practical applications.

A bis(salamo)-like chemical sensor H3L ((1E,3E)-2-hydroxy-5-methylisophthalaldehyde O,O -di(3-((((E)-(2-hydroxynaphthalen-1-yl)methylene)amino)oxy)propyl) dioxime) was constructed. H3L is capable of recognizing B4O72- in H2O/DMF (1:9, v/v) solution by both fluorescent and colorimetric channels, bright green fluorescence was turned on when B4O72- was added to H3L and changed from colorless to yellow in natural light. The detection limit was 3.21 × 10-8 M. The identification has good anti-interfering ability, quickly responsive time (5 S) and broad pH detecting range (pH = 5-12). The mechanism of action was determined by 1H NMR titration, infrared spectrometry, HRMS spectra and further elucidated by theory calculations. The fluorescence imaging of bean sprouts and spiked recovery assays of actual water samples demonstrated the practical use of sensor H3L for the detection of B4O72-, which is expected to have applications for the detection of B4O72- in plants and the environment.

A benzimidazole-appended double-armed salamo type fluorescence and colorimetric bifunctional sensor for identification of MnO4- and its applications in actual water samples.

The symmetrically double-armed salamo type fluorescent sensor BMS, incorporating benzimidazole units, was designed and synthesized. Showcasing remarkable specificity and responsiveness to MnO4- within a DMSO:H2O (V/V = 9:1, pH = 7.2) Tris-HCl buffer medium, it enabled dual-channel detection of MnO4- through fluorescent and colorimetric changes. Critical experimental parameters, including detection and quantification thresholds (LOD and LOQ) along with binding affinity constants (Ka), were calculated using the Origin software. A rational interaction mechanism between BMS and MnO4- was deduced, based on fluorescence titration, Electrospray Ionization Mass Spectrometry (ESI-MS), Ultraviolet-Visible Spectroscopy (UV-Vis), Infrared Spectroscopy (IR), Stern-Volmer plots, and Density Functional Theory (DFT) computations. Additionally, the sensor BMS was applied to monitor MnO4- in real water samples. Advancing its practical utility, BMS was fabricated into test strips for the selective detecting of MnO4-.

A nonsymmetrical salamo-like fluorescence chemical sensor for selective identification of Cu2+ and B4O72- ions and practical applications.

An innovative salamo-like fluorescent chemical sensor H2L, has been prepared that can be utilized to selectively detect Cu2+ and B4O72- ions. Cu2+ ions can bind to oxime state nitrogen and phenol state oxygen atoms in the chemosensor H2L, triggering the LMCT effect leading to fluorescence enhancement. The crystal structure of the copper(II) complex, named as [Cu(L)], has been achieved via X-ray crystallography, and the sensing mechanism has been confirmed by further theoretical calculations with DFT. Besides, the sensor H2L recognizes B4O72- ions causing an ICT effect resulting in bright blue fluorescence. Moreover, the sensor has relatively high selectivity and sensitivity for Cu2+ and B4O72- ions, and the detection limits are 1.02 × 10-7 and 2.06 × 10-7 M, respectively. In addition, the good biocompatibility and excellent water solubility of the sensor H2L make it very advantageous in practical applications, using H2L powder for fingerprint visualization, using H2L to identify the phenomenon of B4O72- ions emitting bright blue fluorescence, making it an ink that can print encrypted messages on A4 paper, in addition to this, based on H2L, the real water sample was tested for Cu2+ ion recognition, and finally the test strip experiment was carried out.

A fluorescent Salamo-Salen-Salamo-Zn(II) sensor for bioimaging and biosensing H2PO4- in Zebrafish and plants.

A newly designed and synthesized Salamo-Salen-Salamo-Zn(II) complex sensor (sensor ZT) was extensively explored for anion sensing studies. The selectivity and sensitivity of the sensor ZT towards H2PO4- ions were based on ICT and CHEF effects, and via displacement pathways in DMSO/H2O (9:1, v/v) medium in the presence of other anions like, PO43-, HPO42- and P2O74- in a short time, separately. The prepared ZT sensor has excellent association constant and low detection lines. The sensing mechanism and binding mode of the sensor were studied by UV-Vis spectroscopy, HR-MS, 1H NMR titration and theory calculations (DFT & TD-DFT) for analytes. The time response and stability of the sensor are also given. Meanwhile, the sensor ZT can be widely used as a simple and effective solid-state optical sensor to detect H2PO4- by intuitive fluorescence changes. In addition, besides the environment can be used as a powerful instrument for detecting H2PO4-, based on the good biocompatibility and tissue permeability of ZT, effectively monitoring H2PO4- in cellular distribution by confocal microscopy using Zebrafish and bean sprout.

A highly selective and sensitive salamo-salen-salamo hybrid fluorometic chemosensor for identification of Zn2+ and the continuous recognition of phosphate anions.

A salamo-salen-salamo hybrid fluorescent chemical sensor (H4L) was synthesized and characterized. It exhibits high selectivity and sensitivity to Zn2+ in physiological pH range. Meanwhile, its zinc(II) complex (L-Zn2+) continuously responses phosphate anions in DMF/H2O (v/v, 9:1) solution. Moreover, the identification processes are explored using characterization methods such as UV-absorption spectra, IR spectra and ESI-MS spectrum. In addition, the coordination mechanism of H2PO4- and Zn2+ were successfully exploited to make the chemical sensor reproducible. In short, the sensors H4L and L-Zn2+ will be promising detection devices for Zn2+ and phosphate anions.

A novel bifunctional-group salamo-like multi-purpose dye probe based on ESIPT and RAHB effect: Distinction of cyanide and hydrazine through optical signal differential protocol.

A novel bifunctional-group multi-purpose dye probe p-TNS has been designed and synthesized. The probe p-TNS has unique excited-state intramolecular proton transfer (ESIPT) and resonance-assisted hydrogen bonding (RAHB) coupled system, was confirmed to detect cyanide and hydrazine by blocking the ESIPT effect. Cyanide can change the fluorescence of the solution from bright green to orange-red (116 nm Stokes shift), while hydrazine causes the bright green fluorescence to be quenched. The recognition mechanism of the probe p-TNS to CN- and N2H4 was proposed reasonably through spectral characterizations and theoretical calculations. Combined with theoretical calculations, it was speculated that the solvent dependence may be caused by the ICT effect in the molecule. The probe p-TNS could be prepared into test strips for the detection of cyanide and hydrazine. In addition, the probe molecule can also be used to detect trace amounts of cyanide in agricultural products, and respond to gaseous hydrazine by direct contact, indicating that the probe p-TNS has good practical application prospects. Therefore, this molecular framework provides a new way of thinking about detecting multiple target substances.

Novel single-armed nitrogen-heterocyclic salamo-based fluorescent sensors for the detection of Al3+ and CN.

Two novel single-armed nitrogen-heterocyclic chemosensors with basically similar structures, PDNS and PZNS, were synthesized to specifically identify Al3+ in DMS:H2O (1:1 v/v) solution by fluorescence emission spectroscopy, and the colour of PDNS and PZNS changed from yellow to colorless when Al3+ was added under daylight. This is the first time that nitrogen-heterocyclic is introduced into salamo-based chemical sensor. At excitation wavelengths of 361 and 365 nm, solutions of PDNS and PZNS changed to intense green-blue fluorescence. Furthermore, it was found that PDNS/PZNS and Al3+ have excellent binding capacity, the lower limit of detection (LOD = 6.25 × 10-9/1.26 × 10-9 mol·dm-3) is also calculated. In addition, sensor PZNS can detect Al3+ in a solution system with up to 95% water content and applicable pH range is 3-12. Compared to other salamo-based sensors, PZNS and PDNS have broader detection conditions and wider utilities. PZNS can also identify CN- in fluorescence spectrum. PZNS can be used for detection of Al3+ in aqueous systems in daily production and life.

Synthesis and luminescence properties of lanthanide complexes with a new tripodal ligands featuring salicylamide arms.

A series of luminescent lanthanide complexes with a new tripodal ligand featuring salicylamide arms, 2,2',2''-nitrilotris(2-furfurylaminoformylphenoxy)triethylamine (L), were synthesized and characterized by elemental analysis, IR and molar conductivity measurements. Photophysical properties of the complexes were studied by means of UV-vis absorption and steady-state luminescence spectroscopy. Excited-state luminescence lifetimes and quantum yield of the complexes were determined. Luminescence studies demonstrated that the tripodal ligand featuring salicylamide arms exhibits a good antennae effect with respect to the Tb(III) and Dy(III) ion due to efficient intersystem crossing and ligand to metal energy transfer. From a more general perspective, this work offers interesting perspectives for the development of efficient luminescent stains and enlarges the arsenal for developing novel luminescent lanthanide complexes of salicylamide derivatives.

Bis{(E)-2-[(2-chloro-3-pyrid-yl)imino-meth-yl]-6-meth-oxy-phenolato-κN,O}copper(II).

In the title mononuclear copper(II) complex, [Cu(C(13)H(10)ClN(2)O(2))(2)], the Cu(II) ion, lying on an inversion center, is four-coordinated in a trans-CuN(2)O(2) square-planar geometry by two phenolate O and two imino N atoms from two symmetry-related N,O-bidentate Schiff base ligands. The shortest Cu⋯Cu distance is 7.5743 (9) Å. However, there are weak intra-molecular electrostatic inter-actions between the Cu atom and the Cl atom of the ligand, with a Cu⋯Cl distance of 3.3845 (9) Å.

Bis{(E)-2-[1-(eth-oxy-imino)-eth-yl]-1-naphtho-lato-κN,O}copper(II).

In the title complex, [Cu(C(14)H(14)NO(2))(2)], the discrete complex mol-ecules have crystallographic inversion symmetry. The slightly distorted square-planar coordination sphere of the Cu(II) atom comprises two phenolate O atoms and two oxime N atoms from two bidentate-chelate 2-[1-(eth-oxy-imino)-eth-yl]-1-naphtho-late O-ethyl oxime (L(-)) ligands [Cu-O = 1.8919 (17) Šand Cu-N = 1.988 (2) Å]. The two naphthalene ring systems in the mol-ecule are parallel, with a perpendicular inter-planar spacing of 1.473 (2) Å, while each complex unit forms links to four other mol-ecules via inter-molecular methyl C-H⋯π inter-actions, giving an infinite cross-linked layered supra-molecular structure.