The main objective of the current project is the synthesis and characterization of new compounds containing the P=C-P=E or P=C=P=E (E=chalcogen) units stabilized with various organic groups on the phosphorus atoms and their use as ligands to two different d-block metal fragments or a transition metal and a p-metal or semimetal from group 14. The diphosphapropenes having a dicoordinated trivalent phosphorus atom and a chalcogen atom have two coordination sites, through the lone pairs of the above mentioned atoms. We expect for them to be able to coordinate to transition metals selectively, depending on the hardness of the d-block metal to one or the other atom. By choosing the proper metal we could obtain species with two different metals, or a metal and a semimetal from the group 14 (Si, Ge, Sn). For instance, the preference of gold fragments to coordinate to phosphorus as well as sulfur is well known, while the bonding with oxygen is less favorable. On the other hand, if an oxygen atom is bonded on the phosphaalkenyl unit, coordination towards Fe or Co metal fragments can be favored. Although a number of compounds underlining the coordination properties of this class of diphosphapropenes have been described in the literature, no mixed-metal coordination compound with this class of ligands have been reported up to date. Furthermore, depending on the nature of the metal (or semimetal) coordinated to the diphosphapropene ligand, we can modulate their properties towards compounds with possible biological activity.

The results of the research will be disseminated through minimum of 4 scientific articles in journals with impact factor, published in top 50%, red and yellow areas, according to the scores of influence (AIS). The participation of the team members to conferences (2 participants) in the topic of organometallic and coordination chemistry is also planned in the second and third year of the research project. The research activity performed in each year will be detailed in yearly activity reports (3 reports).

The design, synthesis and characterization of new compounds containing the P=C-P=E with chalcogens (O, S, Se) stabilized with various organic groups. (Objective 1, part I; the objective will continue in the second stage).

Activities 2020:

A.1.1. The design of new diphosophapropenic compounds; the development of new molecular architectures containing the P=C-P=E moiety using scientific data available in the literature.
A.1.2. Computational study (through DFT techniques) of systems containing the P=C-P=E unit (evaluation of stability and electronic features, depending on the nature of the chalcogen atom as well as the organic R groups grafted onto the studied systems).

Estimated results for the 2020 stage: 1 scientific report, the design of the project website.

2020 stage summary:

In the 2020 stage, scientific activities related to activities A1.1 and A.1.2. have been carried out, namely a study of literature which, corroborated with the experience of the team members, led to the design of diphosphaalkenyl derivatives that can present an increased stability and through their multiple coordination sites can lead to mono-, di- or multinuclear coordination derivatives with controlled properties. We also synthesized and characterized 2 diphosphapropenic compounds, possible precursors for diphosphaalenic systems and transition metal ligands, using (and adapting) the methods described in the literature. On the other hand, the DFT analysis was started to determine the geometric parameters and the electronic distribution.

Results obtained in 2020:

(a) Scientific report

(b) Design of the project website

The design, synthesis and characterization of new compounds containing the P=C-P=E with chalcogens (O, S, Se) stabilized with various organic groups. (Objective 1, part II); Assessment of diphosphapropenes as precursors to new diphosphaallene species (Objective 2); Synthesis of bimetallic compounds with diphosphapropenic or diphosphaallenic ligands coordinated to two metal fragments (Objective 3, part I).

Activities 2021:

A.2.1. Synthesis, purification and phisico-chemical characterization of derivatives containing P=C-P=E unit.
A.2.2. Synthesis of coordination compounds containing diphosphapropenic or diphosphaallenic ligands and transition metals and/or a metal or semimetal from group 14.
A.2.3. DFT study of coordination compounds with diphosphapropenic ligands. Conformational analysis and the study regarding the nature and strengths of the coordinative chemical bond.

Estimated results fo the 2021 stage: 1 scientific report, 2 research articles published or accepted for publication in top 50% indexed scientific journals, the attendence of at least one member of the research team to a conference in the field of the project, the updating of the project's website.

2021 stage summary:

Some of the results of the 2021 stage (comparative studies on the reactivity of mono- and diphosphaalkenyl systems towards lithium-organic derivatives) have been published and another important part (assessment of coordination capacity) are being refined for publication.
In the 2021 stage, in order to fulfill the objectives of the research project, all the scientific stages provided in activities A2.1, A2.2 and A.2.3 have been succesfully carried out, namely: synthesis and characterization of new compounds containing the unit P=C-P=E with chalcogens (O, S, Se) stabilized with different organic groups and their characterization; the study of diphosphapropenic compounds as precursors for cumulenic species to deepen the fundamental knowledge on diphosphaalenes (by testing the reactivity of obtained diphosphopropenes towards lithiated derivatives); Obtaining coordinating compounds with diphosphapropenic or diphosphaalene units coordinated to two different d-block metals or two d and p metal fragments. For this purpose, coordination compounds with Au, Cu, Fe, Ni, Zn, Pd were obtained using phosphapropenic derivatives as ligands. It should be noted that results describing the coordination ability of diphosphapropenes towards earth-abundant metals (Cu, Ni, Zn) have not been reported so far in the literature.
The characterisation of the newly obtained species was completed with the study of the in silico coordination capacitiy of the newly obtained diphosphapropenic derivatives by means of DFT computational methods. Throughout the 2021 stage, the main goal was to design new diphosphopropenic species, to synthesize and characterize such species. An important activity was also to find the most effective methods of stabilizing these species, in order to use them as ligands in coordinating compounds.

Results obtained in 2021:

(a) Scientific report.

(b) Scientific articles accepted for publication:

1. The modulation of 9-Chloro-9-Phosphaalkenylchloro-9-Germafluorene reactivity through organolithium reagents, Lavinia Buta, Raluca Septelean*, Albert Soran, Iulia-Andreea Aghion, Ionut-Tudor Moraru, Gabriela Nemes, Polyhedron, 2021, vol 210, available online DOI 10.1016/j.poly.2021.115505.

(c) Conferences:
1. Sinteza și Reactivitatea Unor Noi Derivați Fosfaalchenilici de Tipul P=C-P=Y , R. Septelean, A. Aghion, G. Nemes, Zilele Academice Clujene – 2021, october 21-22, 2021, Cluj-Napoca, oral presentation.

(d) Updatind the project's website.

Synthesis of bimetallic compounds with diphosphapropenic or diphosphaallenic ligands coordinated to two metal fragments (Objective 3, part II); Preliminary studies regarding the biologic activity of newly designed compounds bearing the P=C-P=E or P=C=P=E moieties (Objective 4).

Activities 2022:

A.3.1. The complete structural characterization of obtained coordination comopunds by means of phisico-chemical methods (NMR, MS, X-Ray diffraction, UV-VIS, IR etc.).
A.3.2. Preliminary studies of biological activity of the prepared coordination compounds.

Estimated results for the 2022 stage: 1 scientific final report, 2 research articles published or accepted for publication in top 50% indexed scientific journals, the attendence of at least one member of the research team to a conference in the field of the project, the updating of the project's website.

2022 stage summary:

The 2022 stage had as a main objective the synthesis of coordinative compounds bearing diphosphapropenic or diphosphaallenic ligands coordinated to two different d- or p-block metals and a preliminary study regarding the biological activity of the newly obtained compounds having the P=C-P or P=C-P=E moieties. In this stage of the current research, new diphosphapropenic compounds have been obtained and characterized and their ability to coordinate to metal fragments with tin, germanium and gold has been tested. The obtained compounds were characterized through NMR spectroscopy. The study of coordination ability of phosphaalkenyl compounds was completed by the synthesis of derivatives containing the P=C-Ge unit and transition metal fragments. For this, a series of Au and Pd complexes with phospha- and diphosphaalkenyl ligands were obtained and completely characterized. The complete results of this study have been published this year in a scientific article in the journal POLYHEDRON (Novel coordination compounds featuring 9-chloro-9-phosphaalkenylchloro-9-germafluorene ligands, N. Deak, R. Septelean, L. Buta, I-T Moraru, I-A. Cretoiu, A. Soran, G. Nemes, Polyhedron, Volume 221, 15 July 2022, 115866). The scientific results obtained throughout the 2022 stage were further disseminated by two poster presentations at the 8th INTERNATIONAL CONFERENCE ON NEW TRENDS IN CHEMISTRY, May 16-18, Famagusta, Cyprus: Novel 1,3-Diphosphapropenes And Their Use As Ligands Towards Transition Metal Fragments, Iulia-Andreea Aghion, Raluca-Anamaria Șeptelean, Gabriela-Nicoleta Nemeș and Reactivity Of 9-Chloro-9-Phosphaalkenylchloro-9-Germafluorene Towards Lithium Reagents, Raluca-Anamaria Șeptelean, Iulia-Andreea Aghion, Gabriela-Nicoleta Nemeș. The antibacterian activity of compounds containing the Mes*P=C(Cl)-P(X)Ph2 backbone (where E is an O or S atom) (Objective 4 of the research project) has been tested, in a preliminary phase, through the disk diffusimetric method on E-Coli type cells.

Results obtained in 2022:

(a) Scientific report

(b) Scientific articles accepted for publication:

1. Novel coordination compounds featuring 9-chloro-9-phosphaalkenylchloro-9-germafluorene ligands, Noemi Deak, Raluca Septelean, Lavinia Buta, Ionut-Tudor Moraru, Iulia-Andreea Cretoiu, Albert Soran, Gabriela Nemes, Polyhedron, 2022, vol 221, available online DOI 10.1016/j.poly.2022.115866.

(c) Conferences:
1. Novel 1,3-diphosphapropenes and their use as ligands towards transition metal fragments, Iulia Andreea Aghion, Raluca Anamaria Septelean, Gabriela-Nicoleta Nemes, International Conference on New Trends in Chemistry, Cyprus, may 16-18, 2022, Famagusta, Cyprus, poster presentation.

2. Reactivity of 9-Chloro-Phosphaalkenyl-9-Germafluorene towards Lithium Reagents, Raluca Anamaria Septelean, Iulia Andreea Aghion, Gabriela-Nicoleta Nemes, International Conference on New Trends in Chemistry, Cyprus, may 16-18, 2022, Famagusta, Cyprus, poster presentation.

(d) Updatind the project's website.