Multi-spectroscopic and molecular docking studies on the interaction of new phthalimides with calf-thymus DNA: In vitro free radical scavenging activities

ABSTRACT

In this study, we report the synthesis and biological evaluation of novel phthalimide based Schiff base derivatives as promising antioxidant and DNA-binding agents. The structural investigation of the synthesized compounds was determined by spectral and elemental analysis. In vitro DNA-binding studies of title compounds were carried out by UV–Vis, fluorescence, circular dichroism spectroscopic techniques, cyclic voltammetry, thermal denaturation studies, and hydrodynamic measurements to investigate their potential as DNA-binding agents. The DNA binding constant (K_b) of target compounds was obtained from absorption studies between 1.2 × 10⁵ M^?1 and 1.27 × 10⁵ M^?1, respectively, suggesting that the test compounds have shown good affinity toward calf-thymus DNA. The experimental results of DNA-binding studies reveal a non-intercalative mode of binding between DNA and the synthesized compounds, most probably groove binding. In addition, molecular docking techniques were performed to rationalize the observed binding affinities with the target DNA. Furthermore, antioxidant and free radical scavenging activities of the synthesized compounds were carried out to find out their pharmacological potential. The results indicate that the title compounds displayed good antioxidant activity against DPPH (IC₅₀: 0.727 and 0.656 mg/mL) and H₂O₂ radicals (IC₅₀: 1.072 and 0.911 mg/mL) comparable to standard ascorbic acid.     

Synthesis and Luminescent Properties of Lanthanide Complexes with Structurally Related Novel Multipodal Ligands

To explore the relationship between the structure of the ligands and the luminescent properties of the lanthanide complexes, a series of lanthanide nitrate complexes with two novel structurally related multipodal ligands, 1,3-bis{[(2’-(2-picolylaminoformyl))phenoxyl]methyl}benzene (L ^I ) and 1,2-bis{[(2’-(2-picolylaminoformyl))phenoxyl]methyl}benzene (L ^II ), have been synthesized and characterized by elemental analysis, infrared spectra and molar conductivity measurements. At the same time, the luminescent properties of the Eu(III) and Tb(III) nitrate complexes in solid state and the Tb(III) nitrate complexes in solvents were investigated at room temperature. Under the excitation of UV light, these complexes exhibited characteristic emissions of central metal ions. The lowest triplet state energy levels T₁ of these ligands both match better to the lowest resonance energy level of Tb(III) than to Eu(III) ion. The influence of the structure of the ligands on the luminescent intensity of the complexes was also discussed.     

Spectroscopic Characterization of Oxime Ligands and Their Complexes

New imine–oxime ligands H₃L¹–H₃L³ have been obtained from reactions of the Schiff base ligands H₂B¹–H₂B³ with monochloroglyoxime. Mononuclear copper(II), cobalt(II), nickel(II), vanadyl(IV) and zinc(II) complexes of the imine–oxime ligands H₃L¹–H₃L³ have been prepared and characterized by elemental analyses, infrared and electronic spectra, magnetic moment and molar conductance data. The molar conductance data show that the complexes are non‐electrolytes. When the imine–oxime ligands react with the metal salts in a 2:1 ratio, they behave as dibasic bidentate ligands towards one metal ion. The nickel(II) and zinc(II) complexes are diamagnetic. The ¹H(¹³C)‐nmr spectra of all ligands and nickel(II) and zinc(II) complexes of the ligands H₃L¹–H₃L³ have been recorded. Mass spectra of the imine–oxime ligands and their nickel(II) and zinc(II) complexes were recorded. Some of the ligands and metal complexes have antibacterial activity.     

DNA Binding,Cleavage and Antibacterial Activity of Mononuclear Cu(II), Ni(II) and Co(II) Complexes Derived from Novel Benzothiazole Schiff Bases

A series of novel bivalent metal complexes M(L₁)₂ and M(L₂)₂ where M = Cu(II), Ni(II), Co(II) and L₁ = 2-((benzo [d] thiazol-6-ylimino)methyl)-4-bromophenol [BTEMBP], L₂ = 1-((benzo [d] thiazol-6-ylimino)methyl) naphthalen-2-ol [BTEMNAPP] were synthesized. All the compounds have been characterized by elemental analysis, SEM, Mass, ¹H NMR, ¹³C NMR, UV–Vis, IR, ESR, spectral data and magnetic susceptibility measurements. Based on the analytical and spectral data four-coordinated square planar geometry is assigned to all the complexes. DNA binding properties of these complexes have been investigated by electronic absorption spectroscopy, fluorescence and viscosity measurements. It is observed that these binary complexes strongly bind to calf thymus DNA by an intercalation mode. DNA cleavage efficacy of these complexes was tested in presence of H₂O₂ and UV light by gel electrophoresis and found that all the complexes showed better nuclease activity. Finally the compounds were screened for antibacterial activity against few pathogens and found that the complexes have potent biocidal activity than their free ligands.     

Comparison of the ht Ultraviolet-Visible Spectra of the Copper(Ii) Complexes of Bidentate Schiff Base Ligands

Abstract

The bis(salicylaldiminato)copper(II) complexes of the ligand series of salicylaldimines derived from the condensation of n-alkyl or n-alkyloxy substituted aromatic amines with 2,4-dihydroxybenzaldehyde were synthesized. a series of Schiff base ligands with the general formula 4-X-N-(2,4-dihydroxybenzylidene)-aniline and differing only in substituents were synthesized. Some of these compounds have already been reported in literature. X=OCH₃[1],OC₂H₅[2],C₄H₉[1]. the copper(II) complexes of these ligands having the general formula, copper, bis[o-[N-(p-X-phenyl) formimidoyl]-4-hydroxyphenolato] were also synthesized. the ligands and their complexes, a total of 24 in number, are studied systematically with ultraviolet-visible spectroscopy to examine the effect of various n-alkyl- and n-alkyloxy substituents on the ligands and on their complexes. in the electronic spectrum of these compounds, the bands observed in the 200-450 run region which involve charge transfer π-π? transition were interpreted.     

Tailored Nitroxide Radicals and Biradical Containing <Superscript>13</Superscript>C Enriched Acetylene Groups: ENDOR and DFT Investigation

A specially synthesized nitroxide biradical R₅-C≡¹³C-(p-C₆H₄)₂-¹³C≡C-R₅ (B4) and two radicals, R₅-C≡¹³CH (RCC) and R₅-C≡¹³C-C₆H₅ (RCCPh), where R₅ is 1-oxyl-2,2,5,5-tetramethyl-pyrroline group, have been studied by X- and W-band electron paramagnetic resonance (EPR) spectroscopy, and by W-band electron-nuclear double resonance (ENDOR). Spin density distribution and hyperfine splitting (hfs) constants on ¹³C atoms were experimentally determined and also calculated using ORCA 3.0.3 program package. The biradical and radicals geometries were optimized on UKS/B3LYP/cc-pVDZ level. Hfs constants were calculated using density functional theory (DFT) with PBE0 functional and N07D, and were compared with the experimental value of the hfs constant on ¹³C atoms, measured from ENDOR spectra. It is concluded that at small values of the exchange integral as J ≤ a/2 ≈ 7–8 G, the current quantum chemical approaches do not allow determining precise values of the hfs constants on the ¹³C atoms in the bridge connecting two paramagnetic nitroxide rings of the biradical.     

Synthesis, Characterization, DNA-Binding and Antiproliferative Activity of Nd(III) Complexes With N-(Nitrogen Heterocyclic) Norcantharidin Acylamide Acid

Three novel complexes [Nd(L)(NO₃)(H₂O)₂]·NO₃·2H₂O (HL¹ = N-pyrimidine norcantharidin acylamide acid, C₁₂H₁₃N₃O₄; HL² = N-pyridine norcantharidin acylamide acid, C₁₃H₁₄N₂O₄; HL³ = N-phenyl norcantharidin acylamide acid, C₁₄H₁₅NO₄) were synthesized. HL¹, HL² and HL³ are the ligand of complex(1), complex(2) and complex(3), respectively. Their structures were characterized by elemental analysis, conductivity measurement, infrared spectra and thermogravimetric analysis. The DNA-binding properties of the complexes have been investigated by fluorescence spectroscopy and viscosity measurements. The results suggest that the complexes can bind to DNA by partial intercalation. The liner Stern-Volmer quenching constant K_sq values are 3.3(±0.21)(1), 1.7(±0.19)(2) and 0.9(±0.04)(3), respectively. Complex (1) and (2) have been found to cleave pBR322 plasmid DNA at physiological pH and temperature. The test of antiproliferation activity indicates that complex(1) has strong antiproliferative ability against the SMMC7721 (IC₅₀ = 131.7 ± 23.4 μmol·L⁻¹) and A549 (IC₅₀ = 128.4 ± 19.9 μmol·L⁻¹) cell lines. The inhibition rates of complex(2) (IC₅₀ = 86.3 ± 11.3 μmol·L⁻¹) are much higher than that of NCTD (IC₅₀ = 115.5 ± 9.5 μmol·L⁻¹) and HL² (111.0 ± 5.7 μmol·L⁻¹) against SMMC7721 cell lines.     

Antioxidant Activities of Some New Chromonyl-2,4-Thiazolidinediones and Chromonyl-2,4-Imidazolidinediones Having Chromone Cores

The antioxidant properties of 11 new synthesized chromonyl-2,4-thiazolidinediones and chromonyl-2,4-imidazolidinediones (CBs) were investigated. The antioxidant activities and mechanisms of the CBs interaction with reactive oxygen species (ROS) were clarified using various in vitro antioxidant assay methods including superoxide anion radical ( $ \mathrm{O}\overline{{}_2^{\bullet }} $ ), hydroxyl radical (HO^?), 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH^?) scavenging activity and the iron (II)-ferrozine complex formation. The potassium superoxide/18-crown-6 ether dissolved in dimethylsulfoxide (DMSO) was applied as a source of superoxide anion radical. Hydroxyl radicals were produced in the Fenton-like reaction Fe(II)+H₂O₂. Chemiluminescence, spectrophotometry, and electron paramagnetic resonance (EPR) spectroscopy using 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) as spin trap were applied as the measurement techniques. The CBs examined that exhibited good free radical scavenging activity also showed strong total antioxidant power capacity. Possible mechanisms of antioxidation are proposed to explain the differences in the experimental results between the chromone derivatives with imidazolidine-2,4-dione ring and those with thiazolidine-2,4-dione ring. In conclusion, some of the new CBs are promising to be applied as inhibitors of free radicals.     

Synthesis and investigation of titanium diselenide intercalated with ferrocene and cobaltocene

Single crystals and polycrystals of titanium diselenide TiSe₂ intercalated with ferrocene Fe(η⁵-C₅H₅)₂ and cobaltocene Co(η⁵-C₅H₅)₂ are synthesized. The magnetic susceptibility and electrical resistivity of the intercalation compounds are measured. The results obtained demonstrate that the intercalation brings about the formation of an impurity band with a temperature-dependent width.     

Synthesis,Spectroscopic and Antimicrobial Studies of Lead (II) Complexes of Schiff Bases Derived From Amino Acids and Isatins

A new series of lead (II) complexes have been synthesized with Schiff bases derived from isatins and amino acids. These ligands act as bidentate species and coordinate to the metal atom through the azomethine nitrogen and carboxylate oxygen atom via deprotonation. The synthesized complexes have been characterized by elemental analysis, conductance measurements, and molecular weight determinations. The mode of bonding of the complexes has been suggested on the basis of infrared, UV-visible, and ¹H- and ¹³C-NMR spectroscopy, and probable structures have been assigned to these complexes. Few representative ligands and metal complexes have also been screened for their antifungal and antibacterial activities. Molecular modeling and analysis for bond lengths and bond angles have also been carried out for one of the representative compound, [Pb(L³)₂], to substantiate the proposed structures.     

Carbon-13 NMR Spectra of Some Group VIIB Transition Metal Thiocarbonyl and Selenocarbonyl Complexes

Recently, we reported the discovery of the first examples of transition metal selenocarbonyl complexes, (n⁵-C₅H₅) Mn (CO)₂ (CSe) and (n⁶-C₆H₅CO₂CH₂(CO)₂ (CSe).¹ These complexes are particularly interesting because, unlike CO and CS, the diatomic CSe molecule has so far eluded isolation even at very low temperatures,² and so these complexes represent the stabilization of a chemically unstable species through coordination to a metal (cf. metal carbene complexes). We have also synthesized several thiocarbonyl complexes of the same type,^3,4 as well as the analogous rhenium selenocarbonyl complexes.⁴ While many detailed studies of the ¹³C nmr spectra of transition metal carbonyls have appeared in the literature over the past few years, there have been no such studies for the closely related thiocarbonyls and selenocarbonyls, although a few isolated data have been reported recently for metal thiocarbonyls.^5,6 In this communication, we report the ¹³C nmr spectra of the isoelectronic series of complexes, (n⁵-C₅H₄R) M(COI)₂ (CX) (M = Mn, R = H, CH₃; M = Re, R = H; X = O,S, Se).     

Electrical conductivity, DSC, XRD, and 7Li NMR studies of rotator crystals n-C21H43COOLi x K(1 − x) (0.33 ≤ x ≤ 0.50), n-C m H(2m + 1)COOLi, and n-C m H(2m + 1)COOK (m = 13, 15, 17, 19, and 21)

Differential scanning calorimetry (DSC) thermograms, X-ray diffraction (XRD) analysis, electrical conductivity (σ), and ⁷Li NMR spectroscopy characterization of n-C _m H_(2m?+?1)COOM solids (M = Li, Na, K; m?=?13, 15, 17, 19, 21) and mixed crystals n-C₂₁H₄₃COOLi _x K_(1???x) (0.25?≤?x?≤?0.75) was performed as a function of temperature. DSC thermograms of n-C _m H_(2m?+?1)COOM revealed several solid-solid phase transitions with large entropy changes. Electrical conductivity studies established that n-C _m H_(2m?+?1)COOLi crystals are poor electrical conductors. In contrast, n-C _m H_(2m?+?1)COOK salts were found to have σ values of 10^???7–10^???8 S·cm^???1. Since the crystal structures and phase-transition temperatures of both n-C _m H_(2m?+?1)COOLi and n-C _m H_(2m?+?1)COOK crystals were similar, they were able to form mixed crystals with the structure n-C _x H_(2m?+?1)COOLi _x K_(1???x). DSC thermograms of the mixed crystals showed a small entropy change at the melting point (ΔS _mp?<?13 J K^???1 mol^???1), in addition, large ΔS values at the solid-solid phase transition temperature. The σ values obtained for mixed crystals were roughly one order of magnitude greater than those determined for n-C₂₁H₄₃COOK crystals. ⁷Li NMR spectra of the mixed crystals recorded at various temperatures suggested that the self-diffusion of Li^?+? ions was excited in the highest-temperature solid phase. Based on these results, we have classified these mixed crystals as rotator crystals.     

Synthesis, characterization, DNA binding and cleavage studies of mixed-ligand Cu(II) complexes of 2,6-bis(benzimidazol-2-yl)pyridine

Four novel copper(II) complexes of the composition [CuLX] where L = 2,6-bis(benzimidazole-2yl)pyridine, X = dipyridophenazine (L₁), 1,10-phenanthroline (L₂), hydroxyproline (L₃) and 2,6-pyridine dicarboxylic acid (L₄) were synthesized and characterized by using elemental analysis, FT-IR, UV–vis, ESI-MS, molar conductance and magnetic susceptibility measurements. The complexes [CuLL₁](NO₃)₂ [1], [CuLL₂](NO₃)₂ [2], [CuLL₃](NO₃) [3] and [CuLL₄] (NO₃) [4] are stable at room temperature. In DMSO the complexes [1] and [2] are 1:2 electrolytes, [3] and [4] are 1:1 electrolytes. Based on elemental and spectral studies five coordinated geometry is assigned to all the four complexes. The interaction of four copper ion complexes with calf thymus DNA were carried out by UV–vis titrations, fluorescence spectroscopy, thermal melting and viscosity measurements .The binding constant (K_b) of the above four metal complexes were determined as 5.43 × 10⁴ M_,⁻¹ 2.56 × 10⁴ M⁻¹, 1.21 × 10⁴ M⁻¹ and 1.57 × 10⁴ M⁻¹ respectively. Quenching studies of the four complexes indicates that these complexes strongly bind to DNA, out of all complex 1 is binding more strongly. Viscosity measurements indicate the binding mode of complexes with CT DNA by intercalation through groove. Thermal melting studies also support intercalative binding. The nuclease activity of the above metal complexes shows that 1, 2 and 3 complexes cleave DNA through redox chemistry.     

Pressure-Tuning Raman Spectra of the Arene Chromium(0) Chalcocarbonyl Complexes, (η6-C6H5CO2CH3)Cr(CO)2(CX) (X = O,S)

The pressure-tuning Raman spectra of the two methylbenzoate complexes, (η⁶-C₆H₅CO₂CH₃)Cr(CO)₂(CX) (X = O, S), have been examined up to ～35 kbar. Structural changes occurred for both complexes in the 10–15 kbar pressure range, most probably as the result of second-order phase transitions. From the observed pressure dependences, replacement of a CO group in the piano-stool (η⁶-C₆H₅CO₂CH₃)Cr(CO)₃ molecule by a CS group has a marked influence on the Cr-arene ring vibrational modes, and the arene ring clearly plays a role in determining the nature of the Cr-CO and Cr-CS bonding interactions.     

Enhanced fluorescence of Tb(III), Dy(III) perchlorate by salicylic acid in bis(benzoylmethyl) sulfoxide complexes and luminescence mechanism

Two novel ternary rare earth perchlorate complexes had been synthesized by using bis(benzoylmethyl) sulfoxide as first ligand (L=C₆H₅COCH₂SOCH₂COC₆H₅), salicylic acid as second ligand (L^′=C₆H₄OHCOO⁻). The compounds were characterized by elemental analysis, TG-DSC and molar conductivities in DMF solution. The composition was suggested as [REL₅L′](ClO₄)₂·nH₂O (RE=Tb, Dy; n=6, 8 ). Based on IR, ¹HNMR and UV spectra, it showed that the first ligand, bis(benzoylmethyl) sulfoxide (L), bonded with Tb(III), Dy(III) ions by the oxygen atom of sulfinyl group. The second ligand, salicylic acid group (L′), not only bonded with RE(III) ions by one oxygen atom of carboxyl group but also bonded with RE(III) ions by oxygen atom of phenolic hydroxyl group. In bis(benzoylmethyl) sulfoxide system, fluorescent spectra of the complexes showed that the luminescence of Tb(III), Dy(III) ions was enhanced by the second ligand salicylic acid. The ternary complexes had stronger fluorescence than the binary ones where only bis(benzoylmethyl) sulfoxide acted as ligand. Phosphorescent spectra of the two ligands indicated that the coordination of salicylic acid resulted in the matching extent increasing between the triplet state of ligand and excited state of the rare earths. The relationship between fluorescence lifetime and fluorescence intensity was also discussed.     

An Infrared Spectroscopic Study of Crystalline Copper (II) Propionate and Butyrate

Abstract

Abstract: The vibrational spectra of crystalline anhydrous copper (II) propionate and butyrate were studied by FT-IR spectroscopy. A detailed assignment of the spectra of both compounds is presented and discussed. It is shown that the presence of two non-equivalent sets of carboxylate ligands within the crystals gives rise to several band splittings, which are particularly evident in those bands ascribable to normal modes involving predominantly the -C_βH₃ or -C_βH₂-fragments. In addition, the vibrational assignments made for the studied molecules are shown to be very useful to help understanding the much more complex spectra of long chain copper carboxylates.     

The Syntheses,Structures, Fluorescence Properties and Biological Activity of two Novel Zinc(II) Complexes Controlled by the Tripodal Imidazole Ligand

Two new zinc complexes, namely Zn(L¹)ClCH₂NO(1) and {Zn(L²)CH₂NO}_n?N(CH₃)₃?ClO₄(2) (L¹ = 3,5-di(1H-imidazol-1-yl)pyridine L² = 1,3,5-tris(1-imidazolyl) benzene), have been synthesized, and characterized by IR spectra, elemental analysis, and a single crystal X-ray diffraction. Fluorescence spectroscopy indicated that two complexes presented strong DNA binding affinity constants to fish sperm DNA (FS-DNA). Gel electrophoresis assay demonstrated the ability of the complex to cleave the HL-60 DNA. Apoptotic study showed the complex exhibited significant cancer cell(KB) inhibitory rate.     

Optical properties of red, green and blue emitting rare earth benzenetricarboxylate compounds

Red, blue and green emitting rare earth compounds (RE³⁺=Eu³⁺, Gd³⁺ and Tb³⁺) containing the benzenetricarboxylate ligands (BTC) [hemimellitic (EMA), trimellitic (TLA) and trimesic (TMA)] were synthesized and characterized by elemental analysis, complexometric titration, X-ray diffraction patterns, thermogravimetric analysis and infrared spectroscopy. The complexes presented the following formula: [RE(EMA)(H₂O)₂], [RE(TLA)(H₂O)₄] and [RE(TMA)(H₂O)₆], except for Tb-TMA compound, which was obtained only as anhydrous. Phosphorescence data of Gd³⁺-(BTC) complexes showed that the triplet states (T) of the BTC³⁻ anions have energy higher than the main emitting states of the Eu³⁺ (⁵D₀) and Tb³⁺ (⁵D₄), indicating that BTC ligands can act as intramolecular energy donors for these metal ions. The high values of experimental intensity parameters (Ω₂) of Eu³⁺-(BTC) complexes indicate that the europium ion is in a highly polarizable chemical environment. Based on the luminescence spectra, the energy transfer from the T state of BTC ligands to the excited ⁵D₀ and ⁵D₄ levels of the Eu³⁺ and Tb³⁺ ions is discussed. The emission quantum efficiencies (η) of the ⁵D₀ emitting level of the Eu³⁺ ion have been also determined. In the case of the Tb³⁺ ion, the photoluminescence data show the high emission intensity of the characteristic transitions ⁵D₄→⁷F_J (J=0-6), indicating that the BTC ligands are good sensitizers. The RE³⁺-(BTC) complexes act as efficient light conversion molecular devices (LCMDs) and can be used as tricolor luminescent materials.     

A cross-relaxation mechanism of fluorescence quenching in complexes of lanthanide ions with organic ligands

For the first time, direct experimental evidence of a new mechanism for the quenching of fluorescence of organic ligands (L) in complex compounds with lanthanide ions (Ln³⁺) is obtained. By analogy with the mechanism of luminescence quenching upon pair interactions of Ln³⁺ ions in inorganic systems, this mechanism is called the cross-relaxation mechanism. The experiments are performed with complexes of Tb³⁺ with dianions of halogen-substituted fluoresceins (HSFs): 4,5-dibromo-and 4,5-diiodofluorescein, eosin B, eosin, erythrosin, and Rose Bengal in dimethyl sulfoxide. In accordance with this mechanism—exchange energy transfer, L^2?(*S ₁), Tb³⁺(⁷ F ₆)→L^2?(T ₁), Tb³⁺(⁷ F _{5, 4}), allowed by the spin selection rules—an increase in the quantum yield of formation of the triplet state (Φ_T) of a ligand L^2? and a decrease in the quantum yield of fluorescence (Φ_fl) are found to take place upon complexation. The efficiency of this process amounts to ～1 in accordance with the equality Φ_fl+Φ_T=1, valid for solutions of HSFs. The possibility of other processes leading to a similar effect, specifically, recharging of the system (as for complexes of HSFs with Eu³⁺ and ³⁺) is considered. An example of inductive resonance interactions in complexes of HSFs with Pr³⁺ is given. The manifestation of equilibrium between outer-sphere and inner-sphere complexes in the photophysics of complexes of metals with HSFs is discussed.

     

The effect of ligands on the first hyperpolarizabilities of rich d electron molecular system: iridium clusters,a TDDFT study

A systematically varied series of tetrahedral iridium clusters have been studied using a TDDFT method focusing on their electronic and nonlinear optical properties. The clusters W₂Ir₂(CO)₁₀(η⁵-C₅H₄Me)₂ (1), WIr₃(μ-dppe)(CO)₉(η⁵-C₅H₄Me (2), W₂Ir₂(μ-L)(CO)₈(η⁵-C₅H₄Me)₂(L = dppe 3, dppf 4), Ir₄(μ-L)(CO)₁₀(L = dppm 5, dppe 6, Ph₂P(CH₂)₃PPh₂ 7, Ph₂P(CH₂)₄PPh₂ 8, (Ph₂P)₂CHMe 9), Ir₄(CO)₁₀(phen)(phen = 1,10-phenanthroline) (10) exhibit the first static hyperpolarizabilities of medium magnitude (β _tot ～ 10 × 10^?30esu). The origination of β is discussed in terms of the electronic structure calculation and the expanded orbital decomposition scheme. The result suggests the origination of β for all the clusters are mainly d–d electron transitions intra metal skeleton, and d–π* electron transitions from metals to carbonyls. For cluster 5, which contains the ferrocenyl group, the main origination of β involves charge transfer from d orbitals of ferrocene to d orbirals of Ir and W.