Self-assembly of Ru-4 and Ru-8 assemblies by coordination using organometallic Ru(II)(2) precursors: Synthesis, characterization and properties

Coordination-driven self-assembly of binuclear half-sandwich p-cymene ruthenium(II) complexes [Ru-2(mu-eta(4)-C2O4)(MeOH)(2)(eta(6)-p-cymene)(2)](O3SCF3)(2) (1a) or [Ru-2(mu-eta(4)-N,N'-diphenyloxamidato)(MeOH)(2)(eta(6)-p-cymene)(2)]( O3SCF3)(2) (1b) separately with an imidazole-based tetratopic donor L in methanol affords two tetranuclear metallamacrocycles 2a and 2b, respectively. Conversely, the similar combination of L with 2,5-dihydroxy-1,4-benzoquinonato (dhbq) bridged binuclear complex [Ru-2(mu-eta(C6H2O4)-C-4)(MeOH)(2)(eta(6)-p-cymene)(2)](O3SCF3)(2) (1c) in 1:2 molar ratio resulted in an octanuclear macrocyclic cage 2c. All the self-assembled macrocycles 2a-2c were isolated as their triflate salts in high yields and were characterized fully by multinuclear (H-1, C-13 and F-19) NMR, infrared (IR) and electrospray ionization mass spectrometry (ESIMS). In addition, the molecular structure of macrocycle 2a was established unequivocally by single-crystal X-ray diffraction analysis and adopts a tetranuclear rectangular geometry with the dimensions of 5.53 angstrom x 12.39 angstrom. Furthermore, the photo-and electrochemical properties of these newly synthesized assemblies have been studied by using UV-vis absorption and cyclic voltammetry analysis.

Coordination-Driven Self-Assembly of 2D-Metallamacrocycles Using a New Carbazole-Based Dipyridyl Donor: Synthesis, Characterization, and C-60 Binding Study

A new carbazole-based 90 degrees dipyridyl donor 3,6-di(4-pyridylethynyl)carbazole (L) containing carbazole-ethynyl functionality is synthesized in reasonable yield using the Sonagashira coupling reaction. Multinuclear NMR, electrospray ionization-mass spectrometry (ESI-MS), including single crystal X-ray diffraction analysis characterized this 90 degrees building unit. The stoichiometry combination of L with several Pd(II)/Pt(II)-based 90 degrees acceptors (1a-1d) yielded 2 + 2] self-assembled metallacycles (2a-2d) under mild conditions in quantitative yields 1a = cis-(dppf)Pd(OTf)(2); 1b = cis-(dppf)Pt(OTf)(2); 1c = cis-(tmen)Pd(NO3)(2); 1d = 3,6-bis{trans-Pt(C C) (PEt3)(2)(NO3))carbazole]. All these macrocycles were characterized by various spectroscopic techniques, and the molecular structure of 2a was unambiguously determined by single crystal X-ray diffraction analysis. Incorporation of ethynyl functionality to the carbazole backbone causes the resulted macrocycles (2a-2d) to be pi-electron rich and thereby exhibit strong emission characteristics. The macrocycle 2a has a large internal concave aromatic surface. The fluorescence quenching study suggests that 2a forms a similar to 1:1 complex with C-60 with a high association constant of K-sv = 1.0 X 10(5) M-1.

Photoactivated DNA cleavage and anticancer activity of pyrenyl-terpyridine lanthanide complexes

Lanthanide(III) complexes Ln(R-tpy)(acac)(NO3)(2)] (Ln = La(III) in 1, 2; Gd(III) in 4, 5) and Ln(py-tpy)(sacac)(NO3)(2)] (Ln = La(III), Gd(III), 6), where R-tpy is 4'-phenyl-2,2':6',2 `'-terpyridine (ph-tpy in 1, 4), 4'-(1-pyrenyl)-2,2':6',2 `'-terpyridine (py-tpy in 2, 3, 5 and 6), acac is acetylacetonate and sacac is 4-hydroxy-6-{4-(beta-D-glucopyranoside)oxy]phenyl}hex-3,5-dien-2-on ate, were prepared to study their DNA photocleavage activity and photocytotoxicity. Complexes La(ph-tpy)(acac)(E-tOH)(NO3)(2)] (1a) and Gd(ph-tpy)(acac)(NO3)(2)] (4) were characterized by X-ray crystallography. The 1:1 electrolytic complexes bind to calf thymus DNA. The py-tpy complexes cleave pUC19 DNA and exhibit remarkable photocytotoxicity in HeLa cells in UV-A light of 365 nm with apoptotic cell death (IC50: similar to 40 nM in light, >200 mu M in dark). Confocal microscopy using HeLa cells reveal primarily cytosolic localization of the complexes. (C) 2012 Elsevier Masson SAS. All rights reserved.

Low cost calibrated mechanical noisemaker for hearing screening of neonates in resource constrained settings

Background & objectives: There is a need to develop an affordable and reliable tool for hearing screening of neonates in resource constrained, medically underserved areas of developing nations. This study valuates a strategy of health worker based screening of neonates using a low cost mechanical calibrated noisemaker followed up with parental monitoring of age appropriate auditory milestones for detecting severe-profound hearing impairment in infants by 6 months of age. Methods: A trained health worker under the supervision of a qualified audiologist screened 425 neonates of whom 20 had confirmed severe-profound hearing impairment. Mechanical calibrated noisemakers of 50, 60, 70 and 80 dB (A) were used to elicit the behavioural responses. The parents of screened neonates were instructed to monitor the normal language and auditory milestones till 6 months of age. This strategy was validated against the reference standard consisting of a battery of tests - namely, auditory brain stem response (ABR), otoacoustic emissions (OAE) and behavioural assessment at 2 years of age. Bayesian prevalence weighted measures of screening were calculated. Results: The sensitivity and specificity was high with least false positive referrals for. 70 and 80 dB (A) noisemakers. All the noisemakers had 100 per cent negative predictive value. 70 and 80 dB (A) noisemakers had high positive likelihood ratios of 19 and 34, respectively. The probability differences for pre- and post- test positive was 43 and 58 for 70 and 80 dB (A) noisemakers, respectively. Interpretation & conclusions: In a controlled setting, health workers with primary education can be trained to use a mechanical calibrated noisemaker made of locally available material to reliably screen for severe-profound hearing loss in neonates. The monitoring of auditory responses could be done by informed parents. Multi-centre field trials of this strategy need to be carried out to examine the feasibility of community health care workers using it in resource constrained settings of developing nations to implement an effective national neonatal hearing screening programme.

Photocytotoxic Oxidovanadium(IV) Complexes of Polypyridyl Ligands Showing DNA-Cleavage Activity in Near-IR Light

Oxidovanadium(IV) complexes VO(pyphen)(L)]Cl2 (1, 2) and VO(pydppz)(L)]Cl2 (3, 4), where L is 1,10-phenanthroline (phen in 1 and 3) and dipyrido3,2-a:2',3'-c]phenazine (dppz in 2 and 4) are prepared and characterized. The crystal structure of VO(pyphen)(phen)](ClO4)2 (1a) shows a six-coordinate VN5O geometry with a VO2+ moiety in which the polypyridyl ligand binds in a meridional fashion and the phen ligand displays a chelating binding mode with an N-donor site trans to the oxidovanadyl group. The complexes show a dd band within 720-750 nm in DMF. The one-electron paramagnetic complexes are 1:2 electrolytes in DMF. The complexes exhibit an irreversible VIV/VIII redox response near -0.85 V vs. SCE in DMF/0.1 M TBAP. The complexes bind to calf thymus (ct) DNA giving Kb values within 7.5 x 104 to 1.1 x 106 M1. The complexes show poor chemical nuclease activity in the dark and exhibit significant DNA-photocleaving activity in near-IR light of 705 and 785 nm forming .OH radicals. Complexes 2-4 show remarkable photocytotoxicity in HeLa cancer cells. FACS analysis of the HeLa cells treated with complex 4 shows cell death as highlighted by the sub G1 peak. Propidium iodide staining data indicate apoptosis as the primary mode of cell death.

Reactions of Titanocene Bis(trimethylsilyl)acetylene Complexes with Carbodiimides: An Experimental and Theoretical Study of Complexation versus C-N Bond Activation

The reaction of the low valent metallocene(II) sources Cp'Ti-2(eta(2)-Me3SiC2SiMe3) (Cp' = eta(5)-cyclopentadienyl, 1a or eta(5)-pentamethylcyclopentadienyl, 1b) with different carbodiimide substrates RN=C=NR' 2-R-R' (R = t-Bu; R' = Et; R = R' = i-Pr; t-Bu; SiMe3; 2,4,6-Me-C6H2 and 2,6-i-Pr-C6H3) was investigated to explore the frontiers of ring strained, unusual four-membered heterometallacycles 5-R. The product complexes show dismantlement, isomerization, or C-C coupling of the applied carbodiimide substrates, respectively, to form unusual mono-, di-, and tetranuclear titanium(III) complexes. A detailed theoretical study revealed that the formation of the unusual complexes can be attributed to the biradicaloid nature of the unusual four-membered heterometallacycles 5-R, which presents an intriguing situation of M-C bonding. The combined experimental and theoretical study highlights the delicate interplay of electronic and steric effects in the stabilization of strained four-membered heterometallacycles, accounting for the isolation of the obtained complexes.

Nuclear targeting terpyridine iron(II) complexes for cellular imaging and remarkable photocytotoxicity

Iron(II) complexes Fe(L)(2)](2+) as perchlorate (1-3) and chloride (1a-3a) salts, where L is 4'-phenyl-2,2':6',2 `'-terpyridine (phtpy in 1, 1a), 4'-(9-anthracenyl)-2,2':6',2 `'-terpyridine (antpy in 2, 2a) and 4'-(1-pyrenyl)-2,2':6',2 `'-terpyridine (pytpy in 3, 3a), were prepared and their photocytotoxicity studied. The diamagnetic complexes 1-3 having an FeN6 core showed an Fe(III)-Fe(II) redox couple near 1.0 V vs. saturated calomel electrode in MeCN-0.1 M tetrabutylammonium perchlorate. Complexes 2 and 3, in addition, displayed a quasi-reversible ligand-based redox process near 0.0 V. The redox and spectral properties are rationalized from the theoretical studies. The complexes bind to DNA in a partial intercalative mode. The pytpy complex efficiently photo-cleaves DNA in green light via superoxide and hydroxyl radical formation. The antpy and pytpy complexes exhibited a remarkable photocytotoxic effect in HeLa cancer cells (IC50, similar to 9 mu M) in visible light (400-700 nm), while remaining essentially nontoxic in dark (IC50, similar to 90 mu M). Formation of reactive oxygen species (ROS) inside the HeLa cells was evidenced from the fluorescence enhancement of dichlorofluorescein upon treatment with the pytpy complex followed by photo-exposure. The antpy and pytpy complexes were used for cellular imaging. Confocal imaging and dual staining study using propidium iodide (PI) showed nuclear localization of the complexes. (c) 2012 Elsevier Inc. All rights reserved.

Photoactivated DNA cleavage and anticancer activity of oxovanadium(IV) complexes of curcumin

Oxovanadi um(IV) complexes VO(Fc-pic)(acac)](ClO4) (1), VO(Fc-pic)(cur)](ClO4) (2), VO(Ph-pic)(acac)](ClO4) (3) and VO(Ph-pic)(cur)](ClO4) (4), where Fc-pic and Ph-pic are ferrocenylmethyl-bis-(2-pyridylmethylamine) (in 1, 2) and bis-(2-pyridylmethyl)benzylamine (in 3, 4), respectively, acac is acetylacetonate anion (in 1, 3) and cur is curcumin anion (in 2, 4) were prepared, characterized and their photo-induced DNA cleavage and anticancer activity studied. The crystal structure of 1 as its PF6 salt (1a) shows the presence of a VO2+ moiety in VO3N3 coordination geometry. The complexes show a d-d band at similar to 790 nm in DMF and display V(IV)/V(III) redox couple near -1.45 V vs. SCE in DMF-0.1 M TBAP. The complexes are avid binders to calf thymus DNA. Complex 2 efficiently photo-cleaves plasmid DNA in near-IR light of 785 nm forming (OH)-O-center dot radicals. The curcumin complexes show photocytotoxicity in HeLa cancer cells in visible light of 400-700 nm with significant cellular uptake within 4 h of incubation time.

Influence of steric effect on the structural aspects of N,N `,N `'-triarylguanidine derived six-membered C,N] palladacycles

Guanidine derived six-membered C,N] palladacycles of the types (C,N)Pd(mu-OC(O)R)](2) (1a-d), (C,N)Pd(mu-Br)](2) (2a,b), cis-(C,N)PdBr(L)] (3a-d, 4, and 5), and ring contracted guanidine derived five-membered C,N] palladacycle, (C,N)PdBr(C NXy)] (6) were prepared in high yield following the established methods with a view aimed at understanding the influence of the substituents on the aryl rings of the guanidine upon the solid state structure and solution behaviour of palladacycles. Palladacycles were characterised by microanalytical, IR, NMR and mass spectral data. The molecular structures of 1a, 1c, 2a, 2b, 3a, 3c, 3d, and 4-6 were determined by single crystal X-ray diffraction data. Palladacycles 1a and 1c were shown to exist as a dimer in transoid in-in conformation in the solid state but as a mixture of a dimer in major proportion and a monomer (kappa(2)-O,O'-OAc) in solution as deduced from H-1 NMR data. Palladacycles 2a and 2b were shown to exist as a dimer in transoid conformation in the solid state but the former was shown to exist as a mixture of a dimer and presumably a trimer in solution as revealed by a variable temperature H-1 NMR data in conjunction with ESI-MS data. The cis configuration around the palladium atom in 3a, 3c, and 3d was ascribed to steric influence of the aryl moiety of =NAr unit and that in 4-6 was ascribed to antisymbiosis. The solution behaviour of 3d was studied by a variable concentration (VC) H-1 NMR data.

Multiple molecular alterations in phosphodegrons 1-3 within AAV2 capsid demonstrates higher hepatic gene transfer efficiency

The success of AAV2 mediated hepatic gene transfer in human trials for diseases such as hemophilia has been hampered by a combination of low transduction efficiency and a robust immune response directed against these vectors. We have previously shown that AAV2 is targeted for destruction in the cytoplasm by the host-cellular kinase/ubiquitination/proteasomal degradation machinery and modification of the serine(S)/threonine(T) kinase and lysine(K) targets on AAV capsid is beneficial. Thus targeted single mutations of S/T>A(S489A, S498A, T251A) and K>R (K532R) improved the efficiency of gene transfer in vivo as compared to wild type (WT)-AAV2 vectors (∼6-14 fold). In the present study, we evaluated if combined alteration of the phosphodegrons (PD), which are the phosphorylation sites recognized as degradation signals by ubiquitin ligases, improves further the gene transfer efficiency. Thus, we generated four multiple mutant vectors (PD: 1+3, S489A+K532R, PD: 1+3, S489A+K532R together with T251 residue which did not lie in any of the phosphodegrons but had shown increased transduction efficiency compared to the WT-AAV2 vector (∼6 fold) and was also conserved in 9 out of 10 AAV serotypes (AAV 1 to 10), PD: 1+3, S489A+K532R+S498A and a fourth combination of PD: 3, K532R+T251. We then evaluated them in vitro and in vivo and compared their gene transfer efficiency with either the WT-AAV2 or the best single mutant S489A-AAV2 vector. The novel multiple mutations on the AAV2 capsid did not affect the overall vector packaging efficiency. All the multiple AAV2 mutants showed superior transduction efficiency in HeLa cells in vitro when compared to either the WT (62-72% Vs 21%) or the single mutant S489A (62-72% Vs 50%) AAV2 vectors as demonstrated by FACS analysis (Fig. 1A). On hepatic gene transfer with 5x10^10 vgs per animal in C57BL/6 mice, all the multiple mutants showed increased transgene expression compared to either the WT-AAV2 (∼15-23 fold) or the S489A single mutant vector (∼2-3 fold) (Fig.1B and C). These novel multiple mutant AAV2 vectors also showed higher vector copy number in murine hepatocytes 4 weeks post transduction, as compared to the WT-AAV2 (∼5-6 Vs 1.4 vector copies/diploid genome) and further higher when compared to the single mutant S489A(∼5-6 fold Vs 3.8 fold) (Fig.1D). Further ongoing studies will demonstrate the therapeutic benefit of one or more of the multiple mutants vectors in preclinical models of hemophilia.

A novel adeno-associated virus serotype (AAV)-8 capsid mutant improves human coagulation factor IX expression in vivo

Recombinant AAV-8 vectors have shown significant promise for hepatic gene therapy of hemophilia B. However, the theme of AAV vector dose dependent immunotoxicity seen with AAV2 vectors earlier seem to re-emerge with AAV8 vectors as well. It is therefore important to develop novel AAV8 vectors that provide enhanced gene expression at significantly less vector doses. We hypothesized that AAV8 during its intracellular trafficking, are targeted for destruction in the cytoplasm by the host-cellular kinase/ubiquitination/proteasomal degradation machinery and modification of specific serine/threonine kinase or ubiquitination targets on AAV8 capsid (Fig.1A) may improve its transduction efficiency. To test this, point mutations at specific serine (S)/threonine (T) > alanine (A) or lysine (K)>arginine (R) residues were generated on AAV8 capsid. scAAV8-EGFP vectors containing the wild-type (WT) and each one of the 5 S/T/K-mutant(S276A, S501A, S671A, T251A and K137R) capsids were evaluated for their liver transduction efficiency at a dose of 5 X 1010 vgs/ animal in C57BL/6 mice in vivo. The best performing mutant was found to be the K137R vector in terms of either the gene expression (46-fold) or the vector copy numbers in the hepatocytes (22-fold) compared to WT-AAV8 (Fig.1B). The K137R-AAV8 vector that showed significantly decreased ubiquitination of the viral capsid had reduced activation of markers of innate immune response [IL-6, IL-12, tumor necrosis factor α, Kupffer cells and TLR-9]. In addition, animals injected with the K137R mutant also demonstrated decreased (2-fold) levels of cross-neutralizing antibodies when compared to animals that received the WT-AAV8 vector. To study further the utility of the novel AAV8-K137R mutant in a therapeutic setting, we delivered human coagulation factor IX (h.FIX) under the control of liver specific promoters (LP1 or hAAT) at two different doses (2.5x10^10 and 1x10^11 vgs per mouse) in 8-12 weeks old male C57BL/6 mice. As can be seen in Fig.1C/D, the circulating levels of h.FIX were higher in all the K137R-AAV8 treated groups as compared to the WT-AAV8 treated groups either at 2 weeks (62% vs 37% for hAAT constructs and 47% vs 21% for LP1 constructs) or 4 weeks (78% vs 56% for hAAT constructs and 64% vs 30% for LP1 constructs) post hepatic gene transfer. These studies demonstrate the feasibility of the use of this novel vector for potential gene therapy of hemophilia B.

Solvent-templated supramolecular isomerism in 2D coordination polymer constructed by (Ni2CoII)-Co-II nodes and dicyanamido spacers: drastic change in magnetic behaviours

Two heterometallic coordination polymers (CPs) have been prepared using (NiL)-L-II](2)Co-II (where H2L = N,N'-bis(salicylidene)-1,3-propanediamine) as nodes and dicyanamido spacers by varying the solvent for synthesis. Structural characterizations revealed that methanol assisted the formation of a two-dimensional (4,4) connected rhombic grid network of (NiL)(2)Co(NCNCN)2](infinity) (1a) whereas relatively less polar acetonitrile afforded a different superstructure {(NiL)(2)Co(NCNCN)(2)]center dot CH3CN}(infinity) (1b) with a two-dimensional (4,4) connected square grid network. The presence of acetonitrile molecules in the structure of 1b seems to change the spatial orientation of the terminal metalloligands NiL] from pseudo-eclipsed in 1a to staggered-like in 1b around the central Co(II). These structural changes in the nodes together with the conformationally flexible dicyanamido spacers, which are cis coordinated to the Co(II) in both trinuclear units, led to the differences in the final 2D network. Variable-temperature magnetic susceptibility measurements revealed that this supramolecular isomerism led to a drastic transition from spin-frustrated antiferromagnetism for 1a to a dominant ferromagnetic behaviour for 1b. The geometrical differences in Ni2Co coordination clusters (CCs) which are scalene triangular in 1a but nearly linear in 1b, are held responsible for the changes of the magnetic properties. The DFT calculations of exchange interactions between metal centres provide a clear evidence of the role played by the fundamental geometrical factors on the nature and magnitude of the magnetic coupling in these pseudo-polymorphic CPs.

Self-assembly of discrete metallamacrocycles employing half-sandwich octahedral diruthenium(II) building units and imidazole-based ligands

Equimolar combination of a series of binuclear half-sandwich p-cymene ruthenium(II) building units Ru-2(mu-eta(4)-C2O4)(MeOH)(2)(eta(6)-p-cymene)(2)](OTf)(2) 1a](OTf)(2), Ru-2(mu-eta(4)-N,N'-diphenyloxamidato)( MeOH)(2)(eta(6)-p-cymene)(2)](OTf)(2) 1b](OTf)(2) and Ru-2(mu-eta(4)-C6H2O4)(MeOH)(2)(eta(6)-p-cymene)(2)](OTf)(2) 1c](OTf)(2) separately with imidazole-based ditopic ligands (L-1-L-2) in methanol yielded a series of tetranuclear metallamacrocycles 2-7](OTf)(4), respectively L-1 = 1,4-bis(imidazole-1-yl)benzene; L-2 = 4,4'-bis(imidazole-1-yl)biphenyl; OTf- = O3SCF3-]. Similarly, the reaction of Ru-2(mu-eta(4)-C2O4)(MeOH)(2)(eta(6)-p-cymene)2](OTf)(2) 1a](OTf)(2) with a triazine-based tritopic ligand 1,3,5-tris(imidazole-1-yl) triazine (L3) in 3: 2 M ratio afforded an unexpected tetranuclear macrocycle 8](OTf)(4) instead of an expected trigonal prismatic cage 8a](OTf)(6). All the self-assembled macrocycles 2-8](OTf)(4) were isolated in moderate to high yields and were fully characterized by multinuclear H-1, F-19] NMR, IR and electrospray ionization mass spectrometry (ESI-MS). In addition, X-ray diffraction study on the single crystals of 3](OTf)(4) and 8](OTf)(4) also indicated the formation 2 + 2] self-assembled macrocycles. Despite the possibility of formation of different conformational isomeric macrocycles (syn-and anti) and polymeric product due to free rotation of ligand sites of imidazole linkers, the selective formation of single conformational isomer (anti) as the only product is quite interesting. Furthermore, the photo-and electrochemical properties of these assemblies have been studied using UV/Vis absorption and cyclic voltammetry analysis. (c) 2013 Elsevier B.V. All rights reserved.

Dynamics of H-atom exchange in stable cis-dihydrogen/hydride complexes of ruthenium( II) bearing phosphine and N-N bidentate ligands

Synthesis and characterization of cis, trans-RuH(eta(2)-H-2)(PPh3)(2)(N-N)]OTf] (N-N = 2,2'-bipyridyl (bpy) 1a, 2,2'-bipyrimidine (bpm) 2a; OTf = trifluoromethane sulfonate (CF3SO3)) complexes are reported. The cis-H-2/hydride ligands are involved in H-atom site exchange between the two moieties. This dynamics was investigated by variable temperature NMR spectral studies based on which the mechanism of the exchange process was deduced. The Delta G(#) for the exchange of H-atoms between the eta(2)-H-2 and hydride ligands was determined to be around 8 and 13 kJ mol(-1), respectively, for 1a and 2a. The H-H distances (d(HH), A) in complexes 1a and 2a have been calculated from the T-1(minimum) and (1)J(H, D) and are found to be 1.07 A (slow) and 0.95 A for 1a and 1.04 A (slow) and 0.94 A for 2a, respectively. The molecular structure of 1a was determined by X-ray crystallography.

A general methodology for calculating mixed mode stress intensity factors and fracture toughness of solder joints with interfacial cracks

Solder joints in electronic packages undergo thermo-mechanical cycling, resulting in nucleation of micro-cracks, especially at the solder/bond-pad interface, which may lead to fracture of the joints. The fracture toughness of a solder joint depends on material properties, process conditions and service history, as well as strain rate and mode-mixity. This paper reports on a methodology for determining the mixed-mode fracture toughness of solder joints with an interfacial starter-crack, using a modified compact mixed mode (CMM) specimen containing an adhesive joint. Expressions for stress intensity factor (K) and strain energy release rate (G) are developed, using a combination of experiments and finite element (FE) analysis. In this methodology, crack length dependent geometry factors to convert for the modified CMM sample are first obtained via the crack-tip opening displacement (CTOD)-based linear extrapolation method to calculate the under far-field mode I and II conditions (f(1a) and f(2a)), (ii) generation of a master-plot to determine a(c), and (iii) computation of K and G to analyze the fracture behavior of joints. The developed methodology was verified using J-integral calculations, and was also used to calculate experimental fracture toughness values of a few lead-free solder-Cu joints. (C) 2014 Elsevier Ltd. All rights reserved.