The transmetalation reactions of a mercury precursor, [Pentyl(N^C^N)HgCl] (19), with selenium halides (SeCl4, SeBr4, and SeCl2) were attempted to obtain the corresponding organoselenium trichloride [Pentyl(N^C^N)SeCl3], tribromide [Pentyl(N^C^N)SeBr3], and monochloride [Pentyl(N^C^N)SeCl], respectively [(N^C^N) = 5-tert-butyl-1,3-bis-(N-pentyl-benzimidazol-2'-yl)phenyl]. However, in all the cases, a very facile ionization of the Se-halogen bond was observed leading to the isolation of a new class of air stable arylselenium(ii) complexes: [Pentyl(N^C^N)Se+]2[HgCl4]2- (20) and [Pentyl(N^C^N)Se+]2[HgBr4]2- (21). This is the first report on the formation of NCN pincer-based arylselenium(ii) cations via the transmetalation route. Similar reactions were further investigated with several tellurium precursors: {TeCl4, TeBr4 and TeI2} which resulted in the formation of analogous aryltellurium(ii) complexes: [Pentyl(N^C^N)Te+]2[HgCl4]2- (22), [Pentyl(N^C^N)Te+][Cl]- (23), [Pentyl(N^C^N)Te+]2[HgBr4]2- (24), [Pentyl(N^C^N)Te+][Br]- (25) and [Pentyl(N^C^N)Te+]4[Hg2Cl4.72I3.28]4- (26). These are only the second set of examples of aryltellurium cations (hypervalent 10-Te-3 species) with the NCN pincer-based ligand, characterised by X-ray crystallographic studies. The crystallographic studies show a strong SeN/TeN intramolecular interaction, which is confirmed by NBO calculations suggesting the donation of a lone pair of electrons on nitrogen to a lone p-vacancy on selenium/tellurium atoms. The analysis based on NPA derived charges indicates that the contribution of SeN interactions to the electrostatic stabilization energy is in the range of 40-60%, whereas TeN interactions have a contribution of about 84% and more, attributed to the differences in the electronegativity of selenium and tellurium. Furthermore, the formation of arylselenium(ii) and aryltellurium(ii) complexes was favoured due to the presence of the σ-hole on the Se/Te centres.

We report controlled doping in graphene monolayers through charge-transfer interaction by trapping selected organic molecules between graphene and underneath substrates. Controllability has been demonstrated in terms of shifts in Raman peaks and Dirac points in graphene monolayers. Under field effect transistor geometry, a shift in the Dirac point to the negative (positive) gate voltage region gives an inherent signature of n- (p-)type doping as a consequence of charge-transfer interaction between organic molecules and graphene. The proximity of organic molecules near the graphene surface as a result of trapping is evidenced by Raman and infrared spectroscopies. Density functional theory calculations corroborate the experimental results and also indicate charge-transfer interaction between certain organic molecules and graphene sheets resulting p- (n-)type doping and reveals the donor and acceptor nature of molecules. Interaction between molecules and graphene has been discussed in terms of calculated Mulliken charge-transfer and binding energy as a function of optimized distance.

We investigate the charge transport mechanism in copper phthalocyanine thin films with and without traps. Previously, charge transport in polycrystalline thin films has been widely described by the multiple trapping and release (MTR) model, without emphasizing the origin of the traps. In this work, polycrystalline organic thin films with and without traps have been grown by engineering different growth conditions. We find that the density of interface states at the grain boundaries can decide the mechanism of charge transport in organic thin films and completely different charge transport mechanisms can be observed in thin films with and without traps.

New bis(selone)‐based metal complexes, [MnLxCly] {M = Pd, L = 3,3′‐[(2‐bromo‐1,3‐phenylene)bis(methylene)]bis(1‐mesityl‐1,3‐dihydro‐2H‐imidazole‐2‐selone) (15), n = 2, x = 2, y = 4, C64H66N8Cl4Br2Se4Pd2) (17); M = Pt, L = 15, n = 2, x = 2, y = 4, C64H66N8Cl4Br2Se4Pt2 (18); M = Au, L = 15, n = 1, x = 1, y = 1, C32H33N4Se2BrAuCl (19)} were synthesized by the reaction of bis(selone) (15) with Pd(COD)Cl2 (yield 31 %), Pt(COD)Cl2 (yield 34 %), and [AuCl(SMe2)] (yield 57 %), respectively. Single‐crystal X‐ray diffraction analysis reveals that 17 and 18 exist as [2+2] dinuclear self‐assembled 24‐membered metallamacrocycles, while the spectroscopic data for the gold(III) complex 19 indicate that it exists as a new organogold(III) bromide, where a facile oxidative addition occurs across the C–Br bond. Natural bond orbital analysis showed the variation of the natural population analysis (NPA) charge on the Se atoms, from negative to positive, after complexation (15: –0.25; 17: 0.08; 18: 0.09–0.13). Moreover, the NPA charge on the metal atom is found to be negative for complexes 17 and 18 (Pd: –0.133 for 17; Pt: –0.23 and –0.251 for 18). However, for complex 19, the gold atom carries a positive charge (0.15).

The NCN palladium­(II) pincer complex [Benzoyl(N∧C∧N)­PdBr] (16) was synthesized by the oxidative addition of Benzoyl(N∧C∧N)Br to Pd­(dba)2 in 85% yield [(N∧C∧N) = 5-tert-butyl-1,3-bis­(N-substituted benzimidazol-2′-yl)­phenyl)]. Then treatment of complex 16 with KI yielded the iodopalladium complex [Benzoyl(N∧C∧N)­PdI] (17) in 92% yield. Furthermore, a series of cationic palladium­(II) complexes, including [Benzoyl(N∧C∧N)­Pd­(MeCN)]+[BF4]− (18), [Benzoyl(N∧C∧N)­Pd­(MeCN)]+[SbF6]− (19), and [Benzoyl(N∧C∧N)­Pd­(OTf)] (20), were prepared in 68–79% yields by the reaction of the neutral palladium­(II) complex (16) with AgBF4, AgSbF6, and AgOTf, respectively. Similarly, previously synthesized Tosyl(N∧C∧N)­PdBr [5-tert-butyl-1,3-bis­(N-tosylbenzimidazol-2′-yl)­phenyl]­palladium bromide (5b) was treated with AgSO3CF3 and AgSbF6 to afford cationic palladium­(II) complexes [Tosyl(N∧C∧N)­Pd­(OTf)] (21) and [Tosyl(N∧C∧N)­Pd­(MeCN)]+[SbF6]− (22) in 41 and 61% yields, respectively. 5-tert-Butyl-1,3-bis­[{(N-tosylbenzimidazol-2′-yl)­phenyl}­palladium­(II)] triflate (21) exhibited an unsupported metallophillic Pd···Pd interaction [3.166(8) Å] that is corroborated by X-ray crystallographic studies. Compared to other cationic palladium complexes, complex 21 was found to be less stable. In Atoms in Molecule (AIM) analysis, the bond critical point (ρ) between Pd and Pd atoms is 0.000865 au, supporting the presence of metallophillic interaction in complex 21. The bond strength of the Pd···Pd bond was also measured by density functional theory calculations that indicated that the calculated bond order was approximately one-fourth of the normal covalent Pd–Pd bond (natural atomic orbital bond order method). All eight complexes, two neutral and six cationic, were characterized by common spectroscopic techniques, and six complexes were corroborated by X-ray diffraction studies.