Quantum coherence governs macroscopic polymorphism in organic semiconductors

Abstract

The wave-particle duality of massive macromolecules -- such as the fullerene C$_{60}$ -- is a well-established quantum phenomenon. However, whether the quantum behavior of large organic molecules actively dictates the macroscopic structure and function of synthetic materials remains unknown. In organic semiconductors, crystal polymorphism fundamentally determines optoelectronic performance, yet classical thermodynamic models consistently fail to resolve the microscopic origins of phase selection. This includes the long-standing anomaly of divergent polymorph formation under identical thermodynamic parameters across different reactor scales. Here we show that the polymorphism of copper phthalocyanine (CuPc, 576 Da) -- a planar macromolecule comparable in mass to C$_{60}$ -- is governed by quantum coherence during atmospheric-pressure organic vapor phase deposition (OVPD). We establish the Dissipative structure field-Induced Multipartite Entanglement (DIME) framework, which integrates ambient blackbody radiation, molecular de Broglie wavelengths, and frontier orbital directionality to model field-driven quantum entanglement. We demonstrate that exceptionally weak environmental decoherence at room temperature preserves the coherence of molecular matter waves, enabling the self-assembly of ultralong ($>1$ cm) single-crystalline $η$-CuPc nanowires. By leveraging the DIME framework to manipulate environmental decoherence, we rationally designed an OVPD reactor to synthesize a previously undiscovered polymorph, designated $ω$-CuPc. Our findings reveal that multipartite quantum entanglement acts as the decisive regulator of organic crystal assembly, opening a deterministic, quantum-level pathway for engineering organic semiconductor polymorphism.

Figures (5)

• Figure 1: Morphological transformation from irregular bulk CuPc to highly ordered omega-CuPc architectures. a, b, Macroscopic photograph (a) and corresponding scanning electron microscopy (SEM) image (b) of the commercial CuPc precursor powder. The initial source material consists of irregular, classically aggregated microparticles exhibiting a broad size distribution and an absence of preferential structural order. c, d, Photograph (c) and SEM image (d) of the novel omega-CuPc polymorph synthesized via atmospheric-pressure organic vapor phase deposition (OVPD). The macroscopic product (c) exhibits a distinct chromic shift, while the nanoscale architecture (d) reveals a profound spontaneous self-assembly into geometrically uniform, high-aspect-ratio 1D nanowires and nanoribbons. This extreme anisotropic growth---departing entirely from the thermodynamic isotropy of the bulk precursor---provides direct physical evidence of the long-range, quantum-coherent molecular stacking along the compressed b-axis dictated by the DIME framework.
• Figure 2: Low-angle X-ray diffraction establishes the distinct double-layer lattice geometry of the novel $\omega$-CuPc phase. Comparative X-ray diffraction (XRD) patterns (Cu K$\alpha$ radiation, $\lambda = 1.5406$ Å) of the newly synthesized $\omega$-CuPc polymorph (red curve) and the $\eta$-CuPc reference phase (black curve). Vertical markers denote the standard characteristic reflections for the classical $\alpha$-CuPc (ICDD PDF #36-1883, blue) and thermodynamically stable $\beta$-CuPc (ICDD PDF #37-1846, magenta) phases. The severe structural deviation of the $\omega$-phase from these established thermodynamic minimums is anchored by its three strongest low-angle experimental peaks at $6.980^\circ$, $7.601^\circ$, and $9.140^\circ$. These primary reflections index with extreme precision to the theoretical $(100)$, $(001)$, and $(010)$ crystal planes of the proposed monoclinic cell. This perfect geometric alignment definitively validates the expanded structural framework of the $\omega$-lattice, mathematically confirming a fundamental departure from classical stacking motifs.
• Figure 3: TEM characterization of $\omega$-CuPc crystals. a, Bright-field TEM image showing the uniform diameter ($\sim$110 nm) of the $\omega$-CuPc crystals, consistent with SEM observations. b, High-resolution TEM (HRTEM) image revealing well-resolved lattice fringes across the entire crystallite, attesting to its excellent crystallinity. The corresponding fast Fourier transform (FFT) pattern (inset, lower left) exhibits sharp, periodic spots that further confirm the long-range structural order. c, Magnified HRTEM view of the region outlined by the red dashed box in b. The measured interplanar spacing of 1.11 nm corresponds precisely to the (001) reflection identified in the X-ray diffraction pattern at $2\theta=7.60^\circ$ (calculated $d=11.62$ Å), providing direct crystallographic verification of the $\omega$-phase.
• Figure 4: Davydov splitting reveals enhanced intermolecular quantum coupling and extended excitonic delocalization in $\omega$-CuPc. Solid-state ultraviolet-visible (UV-Vis) absorption spectra of the novel $\omega$-CuPc polymorph (red curve), the thermodynamically stable $\beta$-CuPc phase (blue curve), and the initial reference CuPc powder (black curve). While the high-energy Soret (B) band is maintained at 337 nm in the $\omega$-phase, the low-energy Q-band region (600–800 nm) demonstrates profound excitonic coupling. The $\omega$-CuPc phase exhibits an unprecedented Davydov splitting of 154 nm, defined by dual absorption maxima at 612 nm and 766 nm with near-equivalent oscillator strengths. In accordance with molecular exciton theory, this extreme splitting magnitude directly reflects maximized intermolecular transfer integrals. This provides quantitative optical validation of the ultra-tight, double-layer b-axis stacking geometry, confirming that the hydrodynamic and triboelectric conditions of the OVPD reactor successfully trap the molecules in a highly coupled, quantum-coherent lattice distinct from the classical $\beta$-phase.
• Figure 5: Vibrational spectroscopic signatures of symmetry breaking and extended pi-conjugation in $\omega$-CuPc. Comparative Fourier-transform infrared (FTIR) transmission spectra (400–1800 cm$^{-1}$) of the newly synthesized $\omega$-CuPc polymorph (red curve), thermodynamically stable $\beta$-CuPc (blue curve), and reference CuPc powder (black curve). While the preservation of core skeletal vibrations (e.g., 728, 1333, and 1505 cm$^{-1}$) confirms the chemical integrity of the phthalocyanine macrocycle, the $\omega$-phase exhibits three distinct crystallographic deviations. In the low-frequency regime, explicit symmetry breaking in the out-of-plane ring deformation modes is evidenced by the emergence of a novel, structure-defining resonance at 780 cm$^{-1}$. In the mid-frequency regime, suppressed inhomogeneous broadening of the in-plane breathing modes (1089, 1165, and 1287 cm$^{-1}$) denotes a highly uniform local dielectric environment and superior long-range crystalline order. Crucially, the primary conjugated C=C stretching vibration exhibits a definitive 4 cm$^{-1}$ red shift, migrating from 1636 cm$^{-1}$ in $\beta$-CuPc to 1632 cm$^{-1}$ in $\omega$-CuPc. This softening of the intramolecular force constant is governed by transition dipole coupling, physically validating the ultra-tight orthogonal pi–pi orbital overlap and extended electron delocalization inherent to the compressed double-layer geometry of the $\omega$-lattice.