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The synthesis and characterization of two novel and isomeric hybrid ferrocenyl/cyrhetrenyl aldimines [(η-CH)Fe{(η-CH)-CH[double bond, length as m-dash]N-(η-CH)}Re(CO)] (1) and [(η-CH)Fe{(η-CH)-N[double bond, length as m-dash]CH-(η-CH)}Re(CO)] (2) are reported. Their X-ray crystal structures reveal that both adopt the E form. However, molecules of 1 and 2 differ in the relative arrangement of the "Fe(η-CH)" and "Re(CO)" units (anti in 1 and syn in 2). This affects the type of intermolecular interactions, the assembly of the molecules and therefore their crystal architecture. Comparative studies of their electrochemical, spectroscopic and photo-physical properties have allowed us to clarify the effect produced by the location of the organometallic arrays (ferrocenyl or cyrhetrenyl) on electronic delocalization, the proclivity of the metals to undergo oxidation and their emissive properties. Theoretical studies based on Density Functional Theory (DFT) calculations on the two compounds have also been carried out in order to rationalize the experimental results and to assign the bands detected in their electronic spectra. The cytotoxic activities of compounds 1 and 2 against human adenocarcinoma cell lines [breast (MCF7 and MDA-MB-231) and colon (HCT-116)] reveal that imine 2 has a greater inhibitory growth effect than 1 and it is ca. 1.8 times more potent than cisplatin in the triple negative MDA-MB 231 and in the cisplatin resistant HCT-116 cell lines. A comparative study of their effect on the normal and non-tumour human skin fibroblast BJ cell lines is also reported.

The understanding of the mean free path (MFP) distribution of the energy carriers in materials (e.g., electrons, phonons, magnons, etc.) provides a key physical insight into their transport properties. In this context, MFP spectroscopy has become an important tool to describe the contribution of carriers with different MFP to the total transport phenomenon. In this work, we revise the MFP reconstruction technique and present a study on the impact of the regularization parameter on the MFP distribution of the energy carriers. By using the L-curve criterion, we calculate the optimal mathematical value of the regularization parameter. The effect of the change from the optimal value in the MFP distribution is analyzed in three case studies of heat transport by phonons. These results demonstrate that the choice of the regularization parameter has a large impact on the physical information obtained from the reconstructed accumulation function, and thus cannot be chosen arbitrarily. The approach can be applied to various transport phenomena at the nanoscale involving carriers of different physical nature and behavior.

A b s t r a c t:The synthesis of novel cyrhetrenyl hydrazones of general formula [Re{(η 5 -C 5 H 4 )-C(R 1 )=NNHR 2 }(CO) 3 ] {with R 1 = H and R 2 = 4-NO 2 -C 6 H 4 (4a), C 6 H 5 (4b) or H (4c) or R 1 = Me and R 2 = 4-NO 2 -C 6 H 4 (5a), C 6 H 5 (5b) or H (5c)} is described. Compounds 4a-4c and 5a-5c were characterized by mass spectrometry and IR spectroscopy. 1 H and 13 C{ 1 H} NMR studies revealed that 4a-4c and 5a-5c adopt the anti-(E) configuration in solution. X-ray crystal structures of compounds 4a and 5c confirmed the trans-arrangement of the cyrhetrenyl "Re(η 5 -C 5 H 4 )(CO) 3 " and the -NHR 2 moieties and the existence of strong hydrogen bonds involving the -NH-unit. Molecular Orbital calculations at a DFT level have also been carried out in order to rationalize the influence of the nature of the substituent R 3 of [R 3 CH=NNH(4-NO 2 -C 6 H 4 )] (R 3 = ferrocenyl, (3a), cyrhetrenyl (4a) and phenyl (6a) on the electronic delocalization, the nucleophilicity of the imine carbon, the polarizability and hyperpolarizability of these compounds, and computational studies using time-dependent density functional (TD-DFT) calculations have also been carried out in order to assign the bands detected in their electronic spectra and to explain the effect produced by the solvent.