[1]Benzothieno[3,2-b][1]benzothiophene-Phthalocyanine Derivatives: A Subclass of Solution-Processable Electron-Rich Hole Transport Materials

The [1]benzothieno[3,2-b][1]benzothiophene (BTBT) planar system was used to functionalize the phthalocyanine ring aiming at synthesizing novel electron-rich π-conjugated macrocycles. The resulting ZnPc-BTBT and ZnPc-(BTBT)₄ derivatives are the first two examples of a phthalocyanine subclass having potential use as solution-processable p-type organic semiconductors. In particular, the combination of experimental characterizations and theoretical calculations suggests compatible energy level alignments with mixed halide hybrid perovskite-based devices. Furthermore, ZnPc-(BTBT)₄ features a high aggregation tendency, a useful tool to design compact molecular films. When tested as hole transport materials in perovskite solar cells under 100 mA cm^-2 standard AM 1.5G solar illumination, ZnPc-(BTBT)₄ gave power conversion efficiencies as high as 14.13 %, irrespective of the doping process generally required to achieve high photovoltaic performances. This work is a first step toward a new phthalocyanine core engineerization to obtain robust, yet more efficient and cost-effective materials for organic electronics and optoelectronics.

Stability of Cubic FAPbI3 from X-ray Diffraction, Anelastic, and Dielectric Measurements

Among the hybrid metal-organic perovskites for photovoltaic applications, FAPbI₃ (FAPI) has the best performance regarding efficiency and the worst regarding stability, even though the reports on its stability are highly contradictory. In particular, since at room temperature the cubic α phase, black and with high photovoltaic efficiency, is metastable against the yellow hexagonal δ phase, it is believed that α-FAPI spontaneously transforms into δ-FAPI within a relatively short time. We performed X-ray diffraction and thermogravimetric measurements on loose powder of FAPI, and present the first complete dielectric and anelastic spectra of compacted FAPI samples under various conditions. We found that α-FAPI is perfectly stable for at least 100 days, the duration of the experiments, unless extrinsic factors induce its degradation. In our tests, degradation was detected after exposure to humidity, strongly accelerated by grain boundaries and the presence of δ phase, but it was not noticeable on the loose powder kept in air under normal laboratory illumination. These findings have strong implications on the strategies for improving the stability of FAPI without diminishing its photovoltaic efficiency through modifications of its composition.

Understanding the influence of disorder on the exciton dynamics and energy transfer in Zn-phthalocyanine H-aggregates

The photophysics of 9(19),16(17),23(24)-tri-tert-butyl-2-[ethynyl-(4-carboxymethyl)phenyl]phthalocyaninatozinc(ii) and its H-aggregates is studied in different solvents by means of ultrafast non-linear optical spectroscopy and computational modeling. In non-coordinating solvents, both stationary and time-resolved spectroscopies highlight the formation of extended molecular aggregates, whose dimension and spectral properties depends on the concentration. In all the explored experimental conditions, time-resolved transient absorption experiments show multi exponential decay of the signals. Additional insights into the excited state relaxation mechanisms of the system is obtained with 2D electronic spectroscopy, which is employed to compare the deactivation channels in the absence or presence of aggregates. In ethanol and diethylether, where only monomers are present, an ultrafast relaxation process among the two non-degenerate Q-states of the molecule is evidenced by the appearance of a cross peak in the 2D-maps. In chloroform or CCl4, where disordered H-aggregates are formed, an energy transfer channel among aggregates with different composition and size is observed, leading to the non-radiative decay towards the lower energy dark state of the aggregates. Efficient coupling between less and more aggregated species is highlighted in two-dimensional electronic spectra by the appearance of a cross peak. The kinetics and intensity of the latter depend on the concentration of the solution. Finally, the linear spectroscopic properties of the aggregate are reproduced using a simplified structural model of an extended aggregate, based on Frenkel Hamiltonian Calculations and on an estimate of the electronic couplings between each dimer composing the aggregate computed at DFT level.

Competition between Polar and Antiferrodistortive Modes and Correlated Dynamics of the Methylammonium Molecules in MAPbI3 from Anelastic and Dielectric Measurements

The mechanisms behind the exceptional photovoltaic properties of the metallorganic perovskites are still debated and include a ferroelectric (FE) state from the ordering of the electric dipoles of the organic molecules. We present the first anelastic (complex Young's modulus) and new dielectric measurements on CH₃NH₃PbI₃, which provide new insight into the reorientation dynamics of the organic molecules and the reason why they do not form a FE state. The permittivity is fitted within the tetragonal phase with an expression that includes the coupling between FE and octahedral tilt modes, indicating that the coupling is competitive and prevents FE ordering. The onset of the orthorhombic phase is accompanied by sharp stiffening, analogous to the drop of permittivity, due to the hindered molecular dynamics. On further cooling, an intense anelastic relaxation process without a dielectric counterpart suggests the reorientation of clusters of molecules with strong antiferroelectric correlations.

Reply to the ‘Comment on “Metal–organic green dye: chemical and physical insight into a modified Zn-benzoporphyrin for dye-sensitized solar cells”’ by R. Steer, RSC Advances, 2018, DOI: 10.1039/c8ra00213d

The authors reply to the comment by R. P. Steer discussing the reasons for their incorrect assignment of the luminescence decay of the novel compound 5,10,15-(triphenyl),20-[ethynyl-(4-carboxy)phenyl]tetrabenzoporphyrinate Zn(ii) (PETBP). Further DFT and TDDFT calculations have been performed on the compound to investigate the possibility of a direct S₂–S₀ decay instead of a S₂–S₁ conversion with a subsequent emission to the ground state. In addition, the presence of traces of very luminescent contaminants of the ring-opened type has been considered on the grounds of calculated absorption and fluorescence spectra. The results of these investigations confirm that the S₂–S₀ emission reported in the commented paper is not attributable to the target molecule but rather to a neglected luminescent impurity.

The authors reply to the comment by R. P. Steer discussing the reasons for their incorrect assignment of the luminescence decay of the novel compound 5,10,15-(triphenyl),20-[ethynyl-(4-carboxy)phenyl]tetrabenzoporphyrinate Zn(ii) (PETBP).

A Ru–Ru pair housed in ruthenium phthalocyanine: the role of a “cage” architecture in the molecule coupling with the Ag(111) surface

A combined experimental and theoretical study on the Ru–Pc dimer on Ag(111) proves surface-to-molecule charge transfer and predicts magnetic moment quenching.

Modifications of an unsymmetrical phthalocyanine: Towards stable blue dyes for dye-sensitized solar cells

A new copper phthalocyanine, namely 9(10),16(17),23(24)-tri-tert-butyl-2-[acetynyl-(4-carboxy)phenyl]phthalocyaninatocopper and its related free base have been synthesized as potential stable blue dyes for dye sensitized solar cells. The molecule structure consists on an unsymmetrically-substituted macrocycle bearing three tert-butyl groups and one phenylethynyl moiety as peripheral substituents and it is analogue to that of a previously published zinc derivative. Chemical and optical characterizations, as well as theoretical calculations of the frontier orbitals of both molecules are discussed. To evaluate the effect of the central metal on the photovoltaic behavior of this dye, the novel molecules have been both tested and confronted with the zinc derivative. This last one has shown efficiency values significantly higher than those previously published with a 2.10% maximum efficiency, while the other two dyes yielded 1.66% and 1.38% maximum efficiency respectively.

Metal–organic green dye: chemical and physical insight into a modified Zn-benzoporphyrin for dye-sensitized solar cells

A novel green benzoporphyrin has been synthesized, characterized, studied by theoretical methods and tested in DSSC devices. Ab initio simulations predict the actual charge displacement during S₀ → S₁ excitation.

TCR Vβ repertoire in an Italian longeval population including centenarians

During the last years, the hypothesis that aging and diseases are two distinct phenomena, and that successful aging is possible for most humans, has been put forward. We studied the TCR Vβ repertoire of T lymphocytes of healthy longevals and centenarians as crossing point of genetic predisposition and environmental effects to longevity, using the Spectra-typing method. TCR Vβ1, Vβ8, and Vβ20 were found to be expanded in the longeval population, compared with the younger control population. This repertoire can have been shaped by the selective action of particular HLA alleles, or by the clonal expansion of specific T cell clones, able to modulate the immune response to endogenous and exogenous antigens. Moreover, the skewed Vβ usage and the clonal expansion seem to be the effects of physiological changes occurring with aging and not pathological signs of malignity.

Iodine doping of substituted μ-carbido iron diphthalocyanines

Hemi and amphi-substituted μ-carbido iron diphthalocyanine having general formula (t- bu ) 4PcFe-C-FePc and (t- bu ) 4PcFe-C-FePc (t- bu )4 have been oxidized with I2. The oxidized compounds have been characterized and their physicochemical properties have been studied; the results obtained lead to assign them the formula [(t- Bu ) 4PcFe-C-FePc ] (I5)0.66 and [[(t- Bu ) 4PcFe ]2 C ]] (I5)0.66 respectively. The conduction properties, related to the role played by the pushing groups inserted in the peripheral macrocycles, are discussed. Moreover, an effective purification method for improving the yield and purity of iron tetra-tert-butyl phthalocyanine is described, the difficulty being able to obtain this precursor with a high purity grade.

High-accuracy Z-scan measurements of the optical nonlinearity of bis-phthalocyanines

The usage of a modified Z-scan setup for the study of optical nonlinearities of bis-phthalocyanines is discussed. The setup leads to the selection of the pure electronic nonlinear optical response purged from other possible contributions such as molecular reorientation or thermal effects. The described experimental method is based on the capability to extract the instantaneous nonlinear response of the sample, by monitoring and managing cumulative effects and taking full advantage of the large number of probing laser pulses. This kind of approach has been applied on some sandwich-type metal bis-phthalocyanines confirming its potential for an in-depth analysis of the nonlinear response of such molecules. First results on titanium, niobium and tin bis-phthalocyanines provide information on the role of the conjugation length in their nonlinear optical response.

Regulatory influence of scaffolds on cell behavior: how cells decode biomaterials

A stem cell is defined as a cell able to self-renew and at the same time to generate one or more specialized progenies. In the adult organism, stem cells need a specific microenvironment where to reside. This tissue-specific instructive microenvironment, hosting stem cells and governing their fate, is composed of extracellular matrix and soluble molecules. Cell-matrix and cell-cell interactions also contribute to the specifications of this milieu, regarded as a whole unitary system and referred to as "niche". For many stem cell systems a niche has been identified, but only partially defined. In regenerative medicine and tissue engineering, biomaterials are used to deliver stem cells in specific anatomical sites where a regenerative process is needed. In this context, biomaterials have to provide informative microenvironments mimicking a physiological niche. Stem cells may read and decode any biomaterial and modify their behavior and fate accordingly. Any material is therefore informative in the sense that its intrinsic nature and structure will anyway transmit a signal that will have to be decoded by colonizing cells. We still know very little of how to create local microenvironments, or artificial niches, that will govern stem cells behavior and their terminal fate. Here we will review some characteristics identifying specific niches and some of the requirements allowing stem cells differentiation processes. We will discuss on those biomaterials that are being projected/engineered/manufactured to gain the informative status necessary to drive proper molecular cross-talk and cell differentiation; specific examples will be proposed for bone and cartilage substitutes.

Synthesis of a novel unsymmetrical Zn(II) phthalocyanine bearing a phenyl ethynyl moiety as sensitizer for dye-sensitized solar cells

A new unsymmetrical zinc phthalocyanine sensitizer has been synthesised. The anchoring of the molecule to nanocrystalline TiO(2) films is realised by a carboxylic group connected to a phenyl ethynyl moiety. Density Functional Theory (DFT) calculations show significant and positive effects of such a functionalization. Electron injection into the semiconductor and photocurrent generation in DSSC are also presented.

X-ray Absorption Spectroscopy Studies of Ruthenoxane Phthalocyanine Derivative HO-[(Pc)RuO](n)()-H

Comprehensive EXAFS investigation carried out on ruthenoxane phthalocyanine and on its chemical precursors ruthenium phthalocyanine dimer and ruthenium bis-pyridine phthalocyanine are reported. The distances around the ruthenium atom were obtained by data analysis and confirm the structural models already proposed for the first two compounds and indicate two pyridines axially coordinated to the central metal for the adduct.

TCR repertoire of suppressor CD8+CD28- T cell populations

The cellular basis of graft rejection and the development of strategies for specific suppression of T cell responses against allogeneic and xenogeneic transplants represents an area of active investigation. Recently, a population of MHC-class I restricted CD8+CD28- T suppressor cells (Ts) which are able to inhibit specifically the proliferative response of allospecific, xenospecific and nominal-antigen specific CD4+ T helper cells (Th) has been identified. We have studied the TCR V beta gene repertoire expressed by CD8+CD28- Ts isolated from allospecific, xenospecific, and nominal antigen-specific T cell lines (TCL). A limited V beta repertoire has been found in all TCLs studied. The most restricted TCR V beta usage was observed within the population of Ts from xenospecific TCLs. The TCR V beta usage within the Ts subset of TCL differs from the TCR repertoire expressed by the CD4+ Th subset of the same TCL. This is consistent with the fact that Ts and Th cells recognize distinct MHC/ antigen complexes. The finding that the TCR repertoire used by Ts is limited opens new avenues for studying the mechanisms of transplant rejection.

Chromosome 6p-encoded HLA-DR2 determination discriminates migraine without aura from migraine with aura

Segregation analysis indicates that migraine without aura (MWoA) and migraine with aura (MWA) have multifactorial inheritance, but involved genetic and environmental factors are largely unknown. A controlled study was performed to assess the HLA-driven liability to migraine and to verify if the heterogeneity between MWoA and MWA is HLA-linked. Forty-five migraine patients (31 MWoA, 14 MWA) and 53 healthy blood donors as controls, coming from the same geographic area, were studied. Tissue typing was performed using the standard complement-dependent microlymphocytotoxicity technique for HLA Class I and by PCR-SSP (Sequences Specific Primers) typing for HLA Class II. Data emerging from the present study showed no altered distribution for HLA Class I A, B, C antigen frequency in migraine (MWoA, MWA) if compared to the control group. HLA Class II DR2 antigen showed a decreased frequency in MWA group if compared with both MWoA (p = 0.01) and control group (p = 0.039, RR = 0.21). These results seem to support the hypothesis of a protective role of DR2 antigen in MWA and provide additional basis for the proposed difference within MWoA and MWA.

Specific suppression of human CD4+ Th cell responses to pig MHC antigens by CD8+CD28- regulatory T cells

Evidence that T cells can down-regulate the immune response by producing or consuming certain cytokines or by lysing APCs or Th cells has been provided in various systems. However, the generation and characterization of suppressor T cell lines have met with limited success. Here we show that xenospecific suppressor T cells can be generated by in vitro stimulation of human T cells with pig APCs. Similar to allospecific suppressors, these xenospecific suppressor T cells carry the CD8+CD28- phenotype and react to MHC class I Ags expressed by the APCs used for priming. TCR spectratyping of T suppressor cells showed oligoclonal usage of TCR-Vbeta families, indicating that xenostimulation of CD8+CD28- T cells results in Ag-driven selection of a limited Vbeta repertoire. Xenospecific T suppressor cells prevent the up-regulation of CD154 molecules on the membrane of Th cells, inhibiting their ability to react against the immunizing MHC class II xenoantigens. The mechanism of this suppression, therefore, appears to be blockade of CD154/CD40 interaction required for efficient costimulation of activated T cells.

Induction of MHC-class I restricted human suppressor T cells by peptide priming in vitro

The induction of regulatory T cells may offer an effective means for specific immunosuppression of autoimmune disease and allograft rejection. The existence of suppressor T cells has been previously documented, yet their mechanism of action remains poorly characterized. Our studies demonstrate that T suppressor (Ts) cell lines can be generated by in vitro immunization of human PBMCs, with synthetic peptides or soluble proteins coupled to beads. Such Ts cells express the CD8+CD28- phenotype and show the following characteristics: (a) antigen specificity and restriction by self MHC Class I molecules; (b) limited TCR V beta gene usage; (c) ability to inhibit antigen-specific, MHC Class II restricted, Th proliferative responses; and (d) capacity to downregulate and/or inhibit the upregulation by Th of CD40, CD80, and CD86 molecules on APCs. The inhibitory activity of Ts on Th proliferation requires the tripartite interaction between Th, Ts, and APCs and results from inefficient costimulation of Th.

HLA and complement factors alleles sharing in Italian couples with recurrent spontaneous abortions

Recurrent Spontaneous Abortion (RSA) is postulated to be due to several factors including immunogenetic mechanisms. Many studies have been conducted on the effect of the MHC region in the reproductive phenomena suggesting an immunological or genetic involvement in RSA. We studied couples with 3 or more abortions among a larger group of couples in which female partners were anti-cardiolipin antibodies negative, resulting in a population of 43 couples typed for HLA-A, B, C, DR, DQ. In 16 of these 43 couples, complement factors C4A, C4B, and Bf were typed. The data shows a statistically significant increase of C4B*Q0 in RSA patients (N = 32) compared with the control population (N = 44) (pc = .00147) and also a statistically significant increase of C4B*Q0 sharing in aborting couples (43.75%) against the expected sharing rate in the control population (1.86%) (p < .001). Frequency increase of C4B*Q0 allele in aborting population leads to the hypothesis that an imbalance of complement factors expression and activity can have detrimental effects on implantation and embryo survival. Additionally, the significant sharing rate of C4B*Q0 in couples with RSA could indicate the existence of a gene in linked to this allele predisposing to RSA and acting in a recessive manner if present in double copies in the fetus.

HLA-DR and -DQ alleles in Italian patients with melanoma

Controversial data have been reported about HLA alleles and susceptibility to melanoma. Our investigation was undertaken to analyze the relationship between HLA alleles distribution in patients with melanoma and susceptibility to the tumor, in order to study the possible correlation between HLA class II DQA1, DQB1 and DRB1 genes involved in immune recognition, and melanoma, usually considered a highly immunogenic tumor. We therefore typed by means of PCR-SSP (sequence-specific primers) 53 Italian patients and 53 healthy random controls coming from the same geographic area. We observed a decrease of all haplotypes bearing DQB1*0301, DQB1*0302 and DQB1*0303 alleles but not of haplotype DRB1*11;DQA1*0501;DQB1*0301. Our results seem to support the hypothesis of a protective role of some DQ3-bearing haplotypic combinations in melanoma.